{"collection":"philosophy-ethics","full_text_available":true,"graph_url":"https://unchartedknowledge.5gfusion.net/v2/api/page/gutenberg_46652/graph","html_url":"https://unchartedknowledge.5gfusion.net/v2/page/gutenberg_46652","id":"gutenberg_46652","license":"Public Domain (US)","rights_basis":"gutenberg_metadata_copyright_false","source":"gutenberg","source_url":"https://www.gutenberg.org/ebooks/46652","summary":null,"tags":["Biology","Category: Philosophy & Ethics","Category: Science - Biology","Evolution (Biology)","Life -- Origin"],"text":"THE\n\n WONDERS OF LIFE\n\n A POPULAR STUDY\n OF BIOLOGICAL PHILOSOPHY\n\n BY\n\n ERNST HAECKEL\n (Ph.D., M.D., LL.D., Sc.D., and Professor at the\n University of Jena)\n\n AUTHOR OF\n \"THE RIDDLE OP THE UNIVERSE\"\n \"THE HISTORY OF CREATION\"\n \"THE EVOLUTION OF MAN\"\n ETC.\n\n TRANSLATED BY\n JOSEPH McCABE\n\n SUPPLEMENTARY VOLUME TO\n \"THE RIDDLE OF THE UNIVERSE\"\n\n [Illustration: LOGO]\n\n HARPER & BROTHERS PUBLISHERS\n\n NEW YORK AND LONDON\n\n 1905\n\n\n\n\n Copyright, 1904, by HARPER & BROTHERS.\n\n _All rights reserved._\n\n Published January, 1905.\n\n\n\n\n CONTENTS\n\n\n PART I.--METHODOLOGICAL SECTION:\n KNOWLEDGE OF LIFE\n\n PAGE\n\n PREFACE v\n\n CHAPTER I\n\n TRUTH 1\n\n\n CHAPTER II\n\n LIFE 27\n\n\n CHAPTER III\n\n MIRACLES 54\n\n\n CHAPTER IV\n\n THE SCIENCE OF LIFE 77\n\n\n CHAPTER V\n\n DEATH 97\n\n\n PART II.--MORPHOLOGICAL SECTION:\n NATURE OF LIFE\n\n\n CHAPTER VI\n\n PLASM 121\n\n\n CHAPTER VII\n\n UNITIES OF LIFE 147\n\n\n CHAPTER VIII\n\n FORMS OF LIFE 170\n\n\n CHAPTER IX\n\n MONERA 190\n\n\n PART III.--PHYSIOLOGICAL SECTION:\n FUNCTIONS OF LIFE\n\n\n CHAPTER X\n\n NUTRITION 210\n\n\n CHAPTER XI\n\n REPRODUCTION 239\n\n\n CHAPTER XII\n\n MOVEMENT 258\n\n\n CHAPTER XIII\n\n SENSATION 287\n\n\n CHAPTER XIV\n\n MENTAL LIFE 315\n\n\n PART IV.--GENEALOGICAL SECTION:\n HISTORY OF LIFE\n\n\n CHAPTER XV\n\n THE ORIGIN OF LIFE 336\n\n\n CHAPTER XVI\n\n THE EVOLUTION OF LIFE 359\n\n\n CHAPTER XVII\n\n THE VALUE OF LIFE 386\n\n\n CHAPTER XVIII\n\n MORALITY 411\n\n\n CHAPTER XIX\n\n DUALISM 433\n\n\n CHAPTER XX\n\n MONISM 452\n\n\n INDEX 475\n\n\n\n\nPREFACE\n\n\nThe publication of the present work on _The Wonders of Life_ has been\noccasioned by the success of _The Riddle of the Universe_, which I\nwrote five years ago. Within a few months of the issue of this study\nof the monistic philosophy, in the autumn of 1899, ten thousand copies\nwere sold. Moreover, the publisher having been solicited on many sides\nto issue a popular edition of the work, more than a hundred thousand\ncopies of this were sold within a year.[1] This extraordinary and--as\nfar as I was concerned--unexpected success of a philosophical work\nwhich was by no means light reading, and which had no particular charm\nof presentation, affords ample proof of the intense interest taken by\neven the general reader in the object of the work--the construction of\na rational and solid philosophy of life.\n\nNaturally, the clear opposition of my monistic philosophy, based\nas it was on the most advanced and sound scientific knowledge, to\nthe conventional ideas and to an outworn \"revelation,\" led to the\npublication of a vast number of criticisms and attacks. During the\nfirst twelve months more than a hundred reviews and a dozen large\npamphlets appeared, full of the most contradictory strictures and the\nmost curious observations. One of the ablest of my pupils, Heinrich\nSchmidt, gave a summary and criticism of them in his _Der Kampf\num die Weltr\u00e4thsel_, in the autumn of 1900. However, the literary\nstruggle went on to assume gigantic proportions when twelve different\ntranslations of the _Riddle_ appeared, and led to an ever-increasing\nagitation in every educated country of the Old and the New World.\n\nI gave a brief reply to the chief of these attacks in April, 1903,\nin the appendix to the popular edition of the _Riddle_. It would be\nuseless to go further into this controversy and meet the many attacks\nthat have since been made. It is a question here of that profound\nand irreconcilable opposition between knowledge and faith, between\na real knowledge of nature and an alleged \"revelation,\" which has\noccupied the thoughtful and inquiring mind for thousands of years.\nI base my monistic philosophy exclusively on the convictions which\nI have gained during fifty years' close and indefatigable study of\nnature and its harmonious working. My dualistic opponents grant only a\nrestricted value to these experiences; they would subordinate them to\nthe fantastic ideas which they have reached by faith in a supernatural\nworld of spirits. An honest and impartial consideration of this\npalpable contradiction discovers it to be irreconcilable--_either_\nscience and experience, or faith and revelation!\n\nFor this reason I do not propose to make any further reply to the\nopponents of _The Riddle of the Universe_, and I am still less disposed\nto take up the personal attacks which some of my critics have thought\nfit to make on me. In the course of this controversy I have grown\npainfully familiar with the means with which it is sought to silence\nthe detested free-thinker--misrepresentation, sophistry, calumny, and\ndenunciation. \"Critical\" philosophers of the modern Kantist school\nvie in this with orthodox theologians. What I have said in this\nconnection of the theologian Loofs, of Halle, the philologist Dennert,\nof Godesberg, and the metaphysician Paulsen, of Berlin, in the appendix\nto the cheap German edition of the _Riddle_, applies equally to many\nother opponents of the same type. These heated partisans may continue\nto attack and calumniate my person as they will; they will not hurt the\nsacred cause of truth in which I labor.\n\nMuch more interesting to me than these attacks were the innumerable\nletters which I have received from thoughtful readers of the _Riddle_\nduring the last five years, and particularly since the appearance\nof a popular edition. Of these I have already received more than\nfive thousand. At first I conscientiously replied to each of these\ncorrespondents, but I had at length to content myself with sending\na printed slip with the intimation that my time and strength did\nnot permit me to make an adequate reply. However, though this\ncorrespondence was very exacting, it afforded a very welcome proof of\nthe lively sympathy of a large number of readers with the aim of the\nmonistic philosophy, and a very interesting insight into the mental\nattitude of the most varied classes of readers. I especially noticed\nthat the same remarks and questions occurred in many of these five\nthousand letters, very often expressed in the same terms. Most of the\ninquiries related to biological questions, which I had cursorily and\ninadequately touched both in _The Riddle of the Universe_ and _The\nHistory of Creation_. The natural desire to remedy these deficiencies\nof my earlier writings and give a general reply to my interrogators was\nthe immediate cause of the writing of the present work on _The Wonders\nof Life_.\n\nI was confirmed in this design by the circumstance that another\nscientist, the botanist Johannes Reinke, of Kiel, had published\ntwo works in which he had treated the general problems of natural\nphilosophy, especially of biology, from a purely dualistic and\nteleological point of view; these works were his _Die Welt als That_\n(1899) and _Einleitung in die theoretische Biologie_ (1902). As both\nthese works are well written and present the principles of dualism and\nteleology with admirable consistency--as far as this is possible--it\nseemed to me that it was desirable to give a thorough exposition of my\nown monistic and causative system.\n\nHence the present work on the wonders of life is, as the title\nindicates, a supplementary volume to _The Riddle of the Universe_.\nWhile the latter undertook to make a comprehensive survey of the\ngeneral questions of science--as cosmological problems--in the light\nof the monistic philosophy, the present volume is confined to the\nrealm of organic science, or the science of life. It seeks to deal\nconnectedly with the general problems of biology, in strict accord with\nthe monistic and mechanical principles which I laid down in 1866 in my\n_General Morphology_. In this I laid special stress on the universality\nof the law of substance and the substantial unity of nature, which I\nhave further treated in the second and fourteenth chapters of _The\nRiddle of the Universe_.\n\nThe arrangement of the vast material for this study of the wonders\nof life has been modelled on that of the _Riddle_. I have retained\nthe division into larger and smaller sections and the synopses of\nthe various chapters. Thus the whole biological content falls into\nfour sections and twenty chapters. I should much have liked to add\nillustrations in many parts of the text to make the subject plainer,\nespecially as regards chapters vii., viii., xi., and xvi.; but this\nwould have led to a considerable increase in the size and price of\nthe book. Moreover, there are now many illustrated works which will\nhelp the reader to go more fully into the various sections of the\nstudy. Among others, my _History of Creation_ (English translation) and\n_Evolution of Man_ (English translation now in course of preparation)\nwill be found helpful in this way. The German reader will also find\nmany illustrations to elucidate the text of this book in my recently\ncompleted work, _Kunstformen der Natur_ (10 parts, with 100 tables,\n1899-1904).\n\nI had said, in the preface to _The Riddle of the Universe_ in 1899,\nthat I proposed to close my study of the monistic system with that\nwork, and that \"I am wholly a child of the nineteenth century, and\nwith its close I draw the line under my life's work.\" If I now seem\nto run counter to this observation, I beg the reader to consider that\nthis work on the wonders of life is a _necessary_ supplement to the\nwidely circulated _Riddle of the Universe_, and that I felt bound to\nwrite it in response to the inquiries of so many of my readers. In this\nsecond work, as in the earlier one, I make no pretension to give the\nreader a comprehensive statement of my monistic philosophy in the full\nmaturity it has reached--for me personally, at least--at the close of\nthe nineteenth century. A subjective theory of the world such as this\ncan, naturally, never hope to have a complete objective validity. My\nknowledge is incomplete, like that of all other men. Hence, even in\nthis \"biological sketch-book,\" I can only offer studies of unequal\nvalue and incomplete workmanship. There still remains the great design\nof embracing all the exuberant phenomena of organic life in one general\nscheme and explaining all the wonders of life from the monistic point\nof view, as forms of one great harmoniously working universe--whether\nyou call this Nature or Cosmos, World or God.\n\nThe twenty chapters of _The Wonders of Life_ were written\nuninterruptedly in the course of four months which I spent at Rapallo,\non the shore of the blue Mediterranean. The quiet life in this tiny\ncoast-town of the Italian Riviera gave me leisure to weigh again all\nthe views on organic life which I had formed by many-sided experience\nof life and learning since the beginning of my academic studies (1852)\nand my teaching at Jena (1861). To this I was stimulated by the\nconstant sight of the blue Mediterranean, the countless inhabitants\nof which had, for fifty years, afforded such ample material for my\nbiological studies; and my solitary walks in the wild gorges of the\nLigurian Apennines, and the moving spectacle of its forest-crowned\nmountain altars, inspired me with a feeling of the unity of living\nnature--a feeling that only too easily fades away in the study of\ndetail in the laboratory. On the other hand, such a situation did not\nallow a comprehensive survey of the boundless literature which has been\nevoked by the immense advances in every branch of biology. However,\nthe present work is not intended to be a systematic manual of general\nbiology. In the revision of the text, on which I was engaged during\nthe summer at Jena, I had to restrict myself to occasional additions\nand improvements. In this I had the assistance of my worthy pupil, Dr.\nHeinrich Schmidt, to whom also I am indebted for the careful revision\nof the proofs.\n\nWhen I completed my seventieth year at Rapallo, on February 16th, I\nwas overwhelmed with a mass of congratulations, letters, telegrams,\nflowers, and other gifts, most of which came from unknown readers of\n_The Riddle of the Universe_ in all parts of the world. If my thanks\nhave not yet reached any of them, I beg to tender them in these lines.\nBut I should be especially gratified if they would regard this work on\nthe wonders of life as an expression of my thanks, and as a literary\ngift in return. May my readers be moved by it to penetrate deeper and\ndeeper into the glorious work of Nature, and to reach the insight of\nour greatest German natural philosopher, Goethe:\n\n \"What greater thing in life can man achieve\n Than that God-Nature be revealed to him?\"\n\n ERNST HAECKEL.\n\n JENA, _June 17, 1904_.\n\n\n\n\nTHE WONDERS OF LIFE\n\n\n\n\nTHE WONDERS OF LIFE\n\n\n\n\nI\n\nTRUTH\n\n Truth and the riddle of the universe--Experience\n and thought--Empiricism and speculation--Natural\n philosophy--Science--Empirical science--Descriptive\n science--Observation and experiment--History and\n tradition--Philosophic science--Theory of knowledge--Knowledge\n and the brain--\u00c6stheta and phroneta--Seat of the soul, or\n organ of thought: phronema--Anatomy, physiology, ontogeny, and\n phylogeny of the phronema--Psychological metamorphoses--Evolution\n of consciousness--Monistic and dualistic theories of\n knowledge--Divergence of the two ways of attaining the truth.\n\n\nWhat is truth? This great question has occupied the more thoughtful of\nmen for thousands of years, and elicited myriads of attempts to answer\nit, myriads of truths and untruths. Every history of philosophy gives a\nlonger or shorter account of these countless efforts of the advancing\nmind of man to attain a clear knowledge of the world and of itself.\nNay, even \"world-wisdom\" itself, or philosophy in the proper sense\nof the word, is nothing but a connected effort to unite the general\nresults of man's investigation, observation, reflection, and thought,\nand bring them to a common focus. Without prejudice and without fear,\nphilosophy would tear the mantle from \"the veiled statue of Sais,\" and\nattain a full vision of the truth. True philosophy, taken in this\nsense, may proudly and justly style itself \"the queen of the sciences.\"\n\nWhen philosophy, as a search for truth in the highest sense, thus\nunites our isolated discoveries and seeks to weld them into one unified\nsystem of the world, it comes at length to state certain fundamental\nproblems, the answer to which varies according to the degree of culture\nand the point of view of the inquirer. These final and highest objects\nof scientific inquiry have been of late comprehended under the title\nof _The Riddle of the Universe_, and I gave this name to the work I\npublished in 1899, which dealt with them, in order to make its aim\nperfectly clear. In the first chapter I dealt briefly with what have\nbeen called \"the seven great cosmic problems,\" and in the twelfth\nchapter I endeavored to show that they may all be reduced to one\nfinal \"problem of substance,\" or one great \"riddle of the universe.\"\nThe general formulation of this problem is effected by blending the\ntwo chief cosmic laws--the chemical law of the constancy of matter\n(Lavoisier, 1789), and the physical law of the constancy of force\n(Robert Mayer, 1842). This monistic association of the two fundamental\nlaws, and establishment of the unified law of substance, has met with\na good deal of agreement, but also with some opposition; but the most\nviolent attacks were directed against my monistic theory of knowledge,\nor against the method I followed in seeking to solve the riddle of\nthe universe. The only paths which I had recognized as profitable\nwere those of experience and thought--or empirical knowledge and\nspeculation. I had insisted that these two methods supplemented each\nother, and that they alone, under the direction of reason, lead to the\nattainment of truth. At the same time I had rejected as false two other\nmuch-frequented paths which purported to lead directly to a profounder\nknowledge, the ways of emotion and revelation; both of these are in\nopposition to reason, since they demand a belief in miracles.\n\n\"All natural science is philosophy, and all true philosophy is natural\nscience. All true science is natural philosophy.\" I expressed in\nthese words the general result of my monistic studies in 1866 (in the\ntwenty-seventh chapter of my _Generelle Morphologie_). I then laid it\ndown as the fundamental principle of the monistic system that the unity\nof nature and the unity of science follow absolutely from any connected\nstudy of modern philosophic science, and I expressed my conviction\nin these terms: \"All human science is knowledge based on experience,\nor empirical philosophy; or, if the title be preferred, philosophic\nempiricism. Thoughtful experience, or thought based on experience, is\nthe only way and method to be followed in the search for truth.\" I\nendeavored to establish these theses conclusively in the first book\nof the _Generelle Morphologie_, which contains (p. 108) a critical\nand methodological introduction to this science. Not only are those\nmethods considered \"which must necessarily supplement each other\" (I.\nEmpiricism and Philosophy; II. Analysis and Synthesis; III. Induction\nand Deduction), but also those \"which necessarily exclude each other\"\n(IV. Dogmatism and Criticism; V. Teleology and Causality, or Vitalism\nand Mechanicism; VI. Dualism and Monism). The monistic principles which\nI developed there thirty-eight years ago have only been confirmed by\nmy subsequent labors, and so I may refer the interested reader to\nthat work. _The Riddle of the Universe_ is in the main an attempt to\nintroduce to the general reader in a convenient form the chief points\nof the monistic system I established. However, the opposition which has\nbeen aroused by the general philosophic observations of the _Riddle_\ncompels me to give a further explanation of the chief features of my\ntheory of knowledge.\n\nAll true science that deserves the name is based on a collection of\nexperiences, and consists of conclusions that have been reached by\na rational connection of these experiences. \"Only in experience is\nthere truth,\" says Kant. The external world is the object that acts\non man's organs of sense, and in the internal sense-centres of the\ncortex of the brain these impressions are subjectively transformed into\npresentations. The thought-centres, or association centres, of the\ncortex (whether or no one distinguishes them from the sense-centres)\nare the real organs of the mind that unite these presentations into\nconclusions. The two methods of forming these conclusions--induction\nand deduction, the formation of arguments and concepts, thought and\nconsciousness--make up together the cerebral function we call reason.\nThese long familiar and fundamental truths, the recognition of which\nI have described for thirty-eight years as the first condition for\nsolving the riddle of life, are still far from being generally\nappreciated. On the contrary, we find them combated by the extreme\nrepresentatives of both tendencies of science. On the one side, the\nempirical and descriptive school would reduce the whole task to\nexperience, without calling in the aid of philosophy; while philosophic\nspeculation, on the other side, would dispense with experience and\nendeavor to construct the world by pure thought.\n\nStarting from the correct principle that all science originally has its\nsource in experience, the representatives of \"experimental science\"\naffirm that their task consists solely in the exact observation of\n\"facts\" and the classification and description of them, and that\nphilosophic speculation is nothing more than an idle play of ideas.\nHence this one-sided sensualism, as Condillac and Hume especially\nmaintained it, affirmed that the whole action of the mind consists in\na manipulation of sense-impressions. This narrow empirical conception\nspread very widely during the nineteenth century, particularly in the\nsecond half, among the rapidly advancing sciences; it was favored by\nthe specialism which grew up in the necessary division of labor. The\nmajority of scientists are still of opinion that their task is confined\nto the exact observation and description of facts. All that goes beyond\nthis, and especially all far-reaching philosophic conclusions from\ntheir accumulated observations, are regarded by them with suspicion.\nRudolph Virchow strongly emphasized this narrow empirical tendency ten\nyears ago. In his speech on the foundation of the Berlin University\nhe explained the \"transition from the philosophic to the scientific\nage\"; he said that the sole aim of science is \"the knowledge of\nfacts, the objective investigation of natural phenomena in detail.\"\nThe former politician seemed to forget that he had maintained a\nprecisely opposite view forty years before (at W\u00fcrtzburg), and that\nhis own great achievement, the creation of cellular pathology, was a\nphilosophic construction--the formation of a new and comprehensive\ntheory of disease by the combination of countless observations and the\nconclusions deduced therefrom.\n\nNo science of any kind whatever consists solely in the description of\nobserved facts. Hence we can only regard it as a pitiful contradiction\nin terms when we find biology classed in official documents to-day as\na \"descriptive science,\" and physics opposed to it as an \"explanatory\nscience.\" As if in both cases we had not, after describing the observed\nphenomena, to pass on to trace them to their causes--that is, to\n_explain_ them--by means of rational inferences! But it is even more\nregrettable to find that one of the ablest scientists of Germany,\nGustav Kirchhoff, has claimed that description is the final and the\nhighest task of science. The famous discoverer of spectrum analysis\nsays in his _Lectures on Mathematical Physics and Mechanics_\n(1877): \"It is the work of science to describe the movements perceived\nin Nature, in the most complete and simplest fashion.\" There is no\nmeaning in this statement unless we take the word \"description\" in a\nquite unusual sense--unless \"complete description\" is meant to include\nexplanation. For thousands of years true science has been, not merely\na simple description of individual facts, but an explanation of them\nby tracing them to their causes. It is true that our knowledge of them\nis always imperfect, or even hypothetical; but this is equally true\nof the description of facts. Kirchhoff's statement is in flagrant\ncontradiction to his own great achievement, the founding of spectrum\nanalysis; for the extraordinary significance of this does not lie in\nthe discovery of the wonderful facts of spectroscopic optics and the\n\"complete description\" of individual spectra, but in the rational\ngrouping and interpretation of them. The far-reaching conclusions that\nhe has drawn from them have opened out entirely new paths to physics\nand chemistry. Hence Kirchhoff is in as sad a plight as Virchow when\nhe formulates so precarious a principle. However, these statements of\nthe two great scientists have done a great deal of harm, as they have\nwidened still more the deep gulf between science and philosophy. It\nmay be of some service if a few thousand of the thoughtless followers\nof \"descriptive science\" are persuaded to refrain from attempts at\nexplanation of facts. But the master-builders of science cannot be\ncontent with the collection of dead material; they must press on to the\nknowledge of causes by a rational manipulation of their facts.\n\nThe accurate and discriminating observation of facts, supported by\ncareful experiment, is certainly a great advantage that modern science\nhas over all earlier efforts to attain the truth. The distinguished\nthinkers of classic antiquity were far superior to most modern\nscientists and philosophers in regard to judgment and reasoning, or\nall the subtler processes of thought; but they were superficial and\nunpractised observers, and were barely acquainted with experiment.\nIn the Middle Ages scientific work degenerated in both its aspects,\nas the dominant creed demanded only faith and the recognition of\nits supernatural revelation, and depreciated observation. The great\nimportance of this as a foundation of real knowledge was first\nappreciated by Bacon of Verulam, whose _Novum Organon_ (1620) laid down\nthe principles of scientific knowledge, in opposition to the current\nscholasticism derived from Aristotle and his _Organon_. Bacon became\nthe founder of modern empirical investigation, not only by making\ncareful and exact observation of phenomena the basis of all philosophy,\nbut also in demanding the supplementing of this by experiment; by\nthis experiment he understood the putting of a question to Nature, as\nit were, which she must herself answer--a kind of observation under\ndefinite and deliberate conditions.\n\nThis more rigorous method of \"exact observation,\" which is hardly\nthree hundred years old, was very strongly aided by the inventions\nwhich enable the human eye to penetrate into the farthest abysses of\nspace and the profoundest depths of smaller bodies--the telescope and\nmicroscope. The great improvement in these instruments during the\nnineteenth century, and the support given by other recent inventions,\nhave led to triumphs of observation in this \"century of science\"\nthat surpassed all anticipation. However, this very refinement of\nthe technique of observation has its drawbacks, and has led to many\nan error. The effort to obtain the utmost accuracy in _objective_\nobservation has often led to a neglect of the part which is played by\nthe _subjective_ mental action of the observer; his judgment and reason\nhave been depreciated in comparison with the acuteness and clearness\nof his vision. Frequently the means has been turned into the end of\nknowledge. In the reproduction of the thing observed the objective\nphotograph, presenting all parts of the object with equal plainness,\nhas been more valued than the subjective design that reproduces only\nwhat is essential and leaves out what is superfluous; yet the latter\nis in many cases (for instance, in histological observation) much more\nimportant and correct than the former. But the greatest fault has been\nthat many of these \"exact\" observers have refrained altogether from\nreflection and judgment on the phenomena observed, and have neglected\nsubjective criticism; hence it is that so often a number of observers\nof the same phenomenon contradict each other, while each one boasts of\nthe \"exactness\" of his observations.\n\nLike observation, experimentation has been wonderfully improved\nof late years. The experimental sciences which make most use of\nit--experimental physics, chemistry, physiology, pathology, etc.--have\nmade astounding progress. But it is just as important in the case of\nexperiment--or observation under artificial conditions--as of simple\nobservation that it be undertaken and carried out with a sound and\nclear judgment. Nature can only give a correct and unambiguous answer\nto the question you put it when it is clearly and distinctly proposed.\nThis is very often not the case, and the experimenter loses himself in\nmeaningless efforts, with the foolish hope that \"something may come\nof it.\" The modern province of experimental or mechanical embryology\nis especially marred by these useless and perverse experiments.\nEqually foolish is the conduct of those biologists who would transfer\nthe experiment that is valuable in physiology to the field of\nanatomy, where it is rarely profitable. In the modern controversy\nabout evolution the attempt is frequently made to prove or refute\nexperimentally the origin of species. It is quite forgotten that the\nidea of species is only relative, and that no man of science can give\nan absolute definition of it. Nor is it less perverse to attempt to\napply experimentation to historical problems where all the conditions\nfor a successful application are lacking.\n\nThe knowledge which we obtain directly by observation and experiment is\nonly sound when it refers to present events. We have to turn to other\nmethods for the investigation of the past--to history and traditions;\nand these are less easily accessible. This branch of science has been\ninvestigated for thousands of years, as far as the history of man\nand civilization, of peoples and states, and their customs, laws,\nlanguages, and migrations, is concerned. In this, the oral and written\ntradition from generation to generation, the ancient monuments, and\ndocuments, and weapons, etc., furnish an abounding empirical material\nfrom which critical judgment can draw a host of conclusions. However,\nthe door to error lies wide open here, as the documents are usually\nimperfect, and the subjective interpretation of them is often no\nclearer than their objective validity.\n\nNatural history, properly so called, or the study of the origin and\npast history of the universe, the earth, and its organic population,\nis much more recent than the history of mankind. Immanuel Kant was\nthe first to lay the foundations of a mechanical cosmogony in his\nremarkable _Natural History of the Heavens_ (1755), and Laplace gave\nmathematical shape to his ideas in 1796. Geology, also, or the story of\nthe evolution of the earth, was not founded until the beginning of the\neighteenth century, and did not assume a definite shape until the time\nof Hoff and Lyell (1830). Later still (1866) were laid the foundations\nof the science of organic evolution, when Darwin provided a sound\nfoundation, in his theory of selection, for the theory of descent\nwhich Lamarck had proposed fifty years before.\n\nIn sharp contrast to this purely empirical method, which is favored\nby most men of science in our day, we have the purely speculative\ntendency which is current among our academic philosophers. The great\nregard which the critical philosophy of Immanuel Kant obtained during\nthe nineteenth century has recently been increased in the various\nschools of philosophy. As is known, Kant affirmed that only a part of\nour knowledge is empirical, or _a posteriori_--that is, derived from\nexperience; and that the rest of our knowledge (as, for instance,\nmathematical axioms) is _a priori_--that is to say, reached by the\ndeductions of pure reason, independently of experience. This error\nled to the further statement that the foundations of science are\nmetaphysical, and that, though man can attain a certain knowledge\nof phenomena by the innate forms of space and time, he cannot grasp\nthe \"thing in itself\" that lies behind them. The purely speculative\nmetaphysics which was built up on Kant's apriorism, and which found its\nextreme representative in Hegel, came at length to reject the empirical\nmethod altogether, and insisted that all knowledge is obtained by pure\nreason, independently of experience.\n\nKant's chief error, which proved so injurious to the whole of\nsubsequent philosophy, lay in the absence of any physiological and\nphylogenetic base to his theory of knowledge; this was only provided\nsixty years after his death by Darwin's reform of the science of\nevolution, and by the discoveries of cerebral physiologists. He\nregarded the human mind, with its innate quality of reason, as a\ncompletely formed entity from the first, and made no inquiry into\nits historical development. Hence, he defended its immortality as a\npractical postulate, incapable of proof; he had no suspicion of the\nevolution of man's soul from that of the nearest related mammals.\nThe curious predisposition to _a priori_ knowledge is really the\neffect of the inheritance of certain structures of the brain, which\nhave been formed in man's vertebrate ancestors slowly and gradually,\nby adaptation to an association of experiences, and therefore of\n_a posteriori_ knowledge. Even the absolutely certain truths of\nmathematics and physics, which Kant described as synthetic judgments _a\npriori_, were originally attained by the phyletic development of the\njudgment, and may be reduced to constantly repeated experiences and\n_a priori_ conclusions derived therefrom. The \"necessity\" which Kant\nconsidered to be a special feature of these _a priori_ propositions\nwould be found in all other judgments if we were fully acquainted with\nthe phenomena and their conditions.\n\nAmong the censures which the academic metaphysicians, especially in\nGermany, have passed on my _Riddle of the Universe_, the heaviest\nis perhaps the charge that I know nothing whatever about the theory\nof knowledge. The charge is correct to this extent, that I do _not_\nunderstand the current dualistic theory of knowledge which is based\non Kant's metaphysics; I cannot understand how their introspective\npsychological methods--disdaining all physiological, histological, or\nphylogenetic foundations--can satisfy the demands of \"pure reason.\" My\nmonistic theory of knowledge is assuredly very different from this.\nIt is firmly and thoroughly based on the splendid advances of modern\nphysiology, histology, and phytogeny--on the remarkable results of\nthese empirical sciences in the last forty years, which are entirely\nignored by the prevailing system of metaphysics. It is on the ground of\nthese experiences that I have adopted the views on the nature of the\nhuman mind which are expounded in the second part of _The Riddle of the\nUniverse_ (chapters vi.-xi.). The following are the chief points:\n\n1. The soul of man is--objectively considered--essentially similar\nto that of all other vertebrates; it is the physiological action or\nfunction of the brain.\n\n2. Like the functions of all other organs, those of the brain are\neffected by the cells, which make up the organ.\n\n3. These brain-cells, which are also known as soul-cells, ganglionic\ncells, or neurona, are real nucleated cells of a very elaborate\nstructure.\n\n4. The arrangement and grouping of these psychic cells, the number of\nwhich runs into millions in the brain of man and the other mammals, is\nstrictly regulated by law, and is distinguished within this highest\nclass of the vertebrates by several characteristics, which can only be\nexplained by the common origin of the mammals from one primitive mammal\n(or pro-mammal of the Triassic period).\n\n5. Those groups of psychic cells which we must regard as the agents of\nthe higher mental functions have their origin in the fore-brain, the\nearliest and foremost of the five embryonic brain-vesicles; they are\nconfined to that part of the surface of the fore-brain which anatomists\ncall the cortex, or gray bed, of the brain.\n\n6. Within the cortex we have localized a number of different mental\nactivities, or traced them to certain regions; if the latter are\ndestroyed, their functions are extinguished.\n\n7. These regions are so distributed in the cortex that one part of\nthem is directly connected with the organs of sense, and receives\nand elaborates the impressions from these: these are the inner\nsense-centres, or sensoria.\n\n8. Between these central organs of sense lie the intellectual\nor thought-organs, the instruments of presentation and thought,\njudgment and consciousness, intellect and reason; they are called\nthe thought-centres, or association-centres, because the various\nimpressions received from the sense-centres are associated, combined,\nand united in harmonious thought by them.[2]\n\nThe anatomic distinction between the two regions of the cortex\nwhich we oppose to each other as the internal sense-centres and the\nthought or association-centres seems to me of the highest importance.\nCertain physiological considerations had for some time suggested\nthis distinction, but the sound anatomic proof of it has only been\nfurnished during the last ten years. In 1894 Flechsig showed that\nthere are four central sense-regions (\"internal sense-spheres,\" or\n\u00e6stheta) in the gray cortex of the brain, and four thought-centres\n(\"association-centres\" or phroneta) between these: the most important\nof the latter, from the psychological point of view, is the \"principal\nbrain,\" or the \"great occipito-temporal association-centre.\" The\nanatomic determination of the two \"psychic regions\" which Flechsig\nfirst introduced was afterwards modified by himself and substantially\naltered by others. The distinguished works of Edinger, Weigert,\nHitzig, and others, lead to somewhat discrepant conclusions. But\nfor the general conception of psychic action, and especially of\nthe cognitive functions, which interests us at present, it is not\nnecessary to have this delimitation of the regions. The chief point\nholds, that we can to-day anatomically distinguish between the two\nmost important organs of mental life; that the neurona, which compose\nboth, differ histologically (or in finer structure) and ontogenetically\n(or in origin); and that even chemical differences (or a different\nrelation to certain coloring matters) may be perceived. We may\nconclude from this that the neurona or psychic cells which compose\nboth organs also differ in their finer structure; there is probably a\ndifference in the complicated fibrils which extend in the cytoplasm\nof both organs, although our coarse means of investigation have not\nyet succeeded in detecting this difference. In order to distinguish\nproperly between the two sets of neurona, I propose to call the\nsensory-cells or sense-centres _\u00e6sthetal cells_, and the thought-cells\nor thought-centres _phronetal cells_. The former are, anatomically and\nphysiologically, the intermediaries between the external sense-organs\nand the internal thought-organs.\n\nTo this anatomic delimitation of the internal sense-centres and\nthought-organs in the cortex corresponds their physiological\ndifferentiation. The sensorium, or sense-centre, works up the external\nsense-impressions that are conveyed by the peripheral sense-organs\nand the specific energy of their sensory nerves; the _\u00e6stheta_, or\nthe central sense-instruments that make up the sensorium, and their\norganic units, the _\u00e6sthetal cells_, prepare the sense-impressions for\nthought and judgment in the proper sense. This work of \"pure reason\" is\naccomplished by the _phronema_ of the thought-centres, the _phroneta_\n(or the various thought-organs that compose it) and their histological\nelements, the phronetal cells, bringing about an association or\ncombination of the prepared impressions. By this important distinction\nwe avoid the error of the older sensualism (of Hume, Condillac,\netc.)--namely, that all knowledge depends on sense-action alone. It\nis true that the senses are the original source of all knowledge;\nbut, in order to have real knowledge and thought, the specific task\nof reason, the impressions received from the external world by the\nsense-organs, and their nerves and centres, must be combined in the\nassociation-centres and elaborated in the conscious thought-centres.\nThen there is the important, but frequently overlooked, circumstance\nthat there is in advance in the phronetal cells of the civilized man\na valuable quality in the shape of inherited potential nerve-energy,\nwhich was originally engendered by the actual sense-action of the\n\u00e6sthetal cells in the course of many generations.\n\nAn impartial and critical study of the action of the brain in\nvarious scientific leaders shows that, as a rule, there is a certain\nopposition, or an antagonistic correlation, between the two sections\nof the highest mental power. The empirical representatives of science,\nor those who are devoted to physical studies, have a preponderant\ndevelopment of the sensorium, which means a greater disposition and\ncapacity for the observation of phenomena in detail. On the other hand,\nthe speculative representatives of what is called mental science and\nphilosophy, or of metaphysical studies, have the phronema more strongly\ndeveloped, which means a preponderant tendency to, and capacity for,\na comprehensive perception of the universal in particulars. Hence it\nis that metaphysicians usually look with disdain on \"materialistic\"\nscientists and observers; while the latter regard the play of ideas\nof the former as an unscientific and speculative dissipation.\nThis physiological antagonism may be traced histologically to the\ncomparative development of the \u00e6sthetal and the phronetal cells in\nthe two cases. It is only in natural philosophers of the first rank,\nsuch as Copernicus, Newton, Lamarck, Darwin, and Johannes M\u00fcller, that\nboth sections are harmoniously developed, and thus the individual is\nequipped for the highest mental achievements.\n\nIf we take the ambiguous term \"soul\" (_psyche_ or _anima_) in the\nnarrower sense of the higher mental power, we may assign as its\n\"seat\" (or, more correctly, its organ), in man and the other mammals,\nthat part of the cortex which contains the phroneta and is made up\nof the phronetal cells; a short and convenient name for this is the\n_phronema_. According to our monistic theory, the phronema is the\norgan of thought in the same sense in which we consider the eye the\norgan of vision, or the heart the central organ of circulation. With\nthe destruction of the organ its function disappears. In opposition\nto this biological and empirically grounded theory, the current\nmetaphysical psychology regards the brain as the seat of the soul,\nonly in a very different sense. It has a strictly dualistic conception\nof the human soul as a being apart, only dwelling in the brain (like\na snail in its shell) for a time. At the death of the brain it is\nsupposed to live on, and indeed for all eternity. The immortal soul,\non this theory (which we can trace to Plato), is an immaterial entity,\nfeeling, thinking, and acting independently, and only using the\nmaterial body as a temporary implement. The well-known \"piano-theory\"\ncompares the soul to a musician who plays an interesting piece (the\nindividual life) on the instrument of the body, and then deserts it, to\nlive forever on its own account. According to Descartes, who insured\nthe widest acceptance for Plato's dualistic mysticism, the proper\nhabitation of the soul in the brain--in the music-room--is the pineal\ngland, a posterior section of the middle-brain (the second embryonic\ncerebral vesicle). The famous pineal gland has lately been recognized\nby comparative anatomists as the rudiment of a single organ of vision,\nthe pineal eye (which is still found in certain reptiles). Moreover,\nnot one of the innumerable psychologists who seek the seat of the\nsoul in some part of the body, after the fashion of Plato, has yet\nformulated a plausible theory of the connection of mind and body and\nthe nature of their reciprocal action. On our monistic principles the\nanswer to this question is very simple, and consonant with experience.\nIn view of its extreme importance, it is advisable to devote at least a\nfew lines to the consideration of the phronema in the light of anatomy,\nphysiology, ontogeny, and phylogeny.\n\nWhen we conceive the phronema as the real \"organ of the soul\" in the\nstrict sense--that is to say, as the central instrument of thought,\nknowledge, reason, and consciousness--we may at once lay down the\nprinciple that there is an anatomical unity of organ corresponding\nto the physiological and generally admitted unity of thought and\nconsciousness. As we assign to this phronema a most elaborate\nanatomical structure, we may call it the organic apparatus of the\nsoul, in the same sense in which we conceive the eye as a purposively\narranged apparatus of vision. It is true that we have as yet only made\na beginning of the finer anatomic analysis of the phronema, and are not\nyet able to mark off its field decisively from the neighboring spheres\nof sense and motion. With the most improved means of modern histology,\nthe most perfect microscopes and coloring methods, we are only just\nbeginning to penetrate into the marvellous structure of the phronetal\ncells and their complicated grouping. Yet we have advanced far enough\nto regard it as the most perfect piece of cell-machinery and the\nhighest product of organic evolution. Millions of highly differentiated\nphronetal cells form the several stations of this telegraphic system,\nand thousands of millions of the finest nerve-fibrils represent\nthe wires which connect the stations with one another and with the\nsense-centres on the one hand, and with the motor-centres on the other.\nComparative anatomy, moreover, acquaints us with the long and gradual\ndevelopment which the phronema has undergone within the higher class\nof the vertebrates, from the amphibia and reptiles up to the birds and\nmammals, and, within the last class, from the monotremes and marsupials\nup to the apes and men. The human brain seems to us to-day to be the\ngreatest marvel that plasm, or the \"living substance,\" has produced in\nthe course of millions of years.\n\nThe remarkable progress which has been made in the last few decades\nin the anatomic and histological investigation of the brain does not\nyet, it is true, enable us to make a clear delimitation of the region\nof the phronema and its relations to the neighboring sensory and\nmotor spheres in the cortex. We must, in fact, assume that there is\nno sharp distinction in the lower stages of the vertebrate soul; in\nthe older and phylogenetically more distant stages they were not yet\ndifferentiated. Even now there are still intermediaries between the\n\u00e6sthetal and phronetal cells. But we may expect with confidence that\nfurther progress in the comparative anatomy of the brain will, with\nthe aid of embryology, throw more and more light on these complicated\nstructures. In any case, the fundamental fact is now empirically\nestablished that the phronema (the real organ of the soul) forms a\ndefinite part of the cortex of the brain, and that without it there can\nbe no reason, no mental life, no thought, and no knowledge.\n\nSince we regard psychology as a branch of physiology, and examine\nthe whole of the phenomena of mental life from the same monistic\nstand-point as all other vital functions, it follows that we can make\nno exception for knowledge and reason. In this we are diametrically\nopposed to the current systems of psychology, which regard psychology,\nnot as a natural science, but as a mental science. In the next chapter\nwe shall see that this position is wholly unjustified. Unfortunately,\nthis dualistic attitude is shared by a number of distinguished modern\nphysiologists, who otherwise adopt the monistic principles; they\ntake the soul to be, in the Cartesian sense, a supernatural entity.\nDescartes--a pupil of the Jesuits--only applied his theory to man,\nand regarded animals as soulless automata. But the theory is quite\nabsurd in modern physiologists, who know from innumerable observations\nand experiments that the brain, or psychic organ, in man behaves\njust as it does in the other mammals, and especially the primates.\nThis paradoxical dualism of some of our modern physiologists may be\npartly explained by the perverse theory of knowledge which the great\nauthority of Kant, Hegel, etc., has imposed on them; and partly by\na concern for the current belief in immortality, and the dread of\nbeing decried as \"materialists\" if they abandon it. As I do not share\nthis belief, I examine and appreciate the physiological work of the\nphroneta just as impartially as I deal with the organs of sense or the\nmuscles. I find that the one is just as much subject as the other to\nthe law of substance. Hence we must regard the chemical processes in\nthe ganglionic cells of the cortex as the real factors of knowledge and\nall other psychic action. The chemistry of the neuroplasm determines\nthe vital function of the phronema. The same must be said of its most\nperfect and enigmatic function, consciousness. Although this greatest\nwonder of life is only directly accessible by the introspective method,\nor by the mirroring of knowledge in knowledge, nevertheless the use of\nthe comparative method in psychology leads us to believe confidently\nthat the lofty self-consciousness of man differs only in degree, and\nnot in kind, from that of the ape, dog, horse, and other higher mammals.\n\nOur monistic conception of the nature and seat of the soul is strongly\nconfirmed by psychiatry, or the science of mental disease. As an\nold medical maxim runs, _Pathologia physiologiam illustrat_--the\nscience of disease throws light on the sound organism. This maxim is\nespecially applicable to mental diseases, for they can all be traced to\nmodifications of parts of the brain which discharge definite functions\nin the normal state. The localization of the disease in a definite part\nof the phronema diminishes or extinguishes the normal mental function\nwhich is discharged by this section. Thus disease of the speech-centre,\nin the third frontal convolution, destroys the power of speech; the\ndestruction of the visual region (in the occipital convolutions) does\naway with the power of sight; the lesion of the temporal convolutions\ndestroys hearing. Nature herself here conducts delicate experiments\nwhich the physiologist could only accomplish very imperfectly or not at\nall. And although we have in this way only succeeded as yet in showing\nthe functional dependence of a certain part of the mental functions on\nthe respective parts of the cerebrum, no unprejudiced physician doubts\nto-day that it is equally true of the other parts. Each special mental\nactivity is determined by the normal constitution of the relevant part\nof the brain, a section of the phronema. Very striking examples of this\nare afforded in the case of idiots and microcephali, the unfortunate\nbeings whose cerebrum is more or less stunted, and who have accordingly\nto remain throughout life at a low stage of mental capacity. These\npoor creatures would be in a very pitiable condition if they had a\nclear consciousness of it, but that is not the case. They are like\nvertebrates from which the cerebrum has been partly or wholly removed\nin the laboratory. These may live for a long time, be artificially\nfed, and execute automatic or reflex (and in part purposive) motions,\nwithout our perceiving a trace of consciousness, reason, or other\nmental function in them.\n\nThe embryology of the child-soul has been known in a general way for\nthousands of years, and has been an object of keen interest to all\nobservant parents and teachers; but it was not until about twenty years\nago that a strictly scientific study was made of this remarkable and\nimportant phenomenon. In 1884 Kussmaul published his _Untersuchungen\n\u00fcber das Seelenleben des neugeborenen Menschen_, and in 1882 W. Preyer\npublished his _Mind of the Child_ [English translation; Dr. J. Sully\nhas several works on the same subject]. From the careful manuals which\nthese and other observers have published, it is clear that the new-born\ninfant not only has no reason or consciousness, but is also deaf, and\nonly gradually develops its sense and thought-centres. It is only by\ngradual contact with the outer world that these functions successively\nappear, such as speech, laughing, etc.; later still come the power of\nassociation, the forming of concepts and words, etc. Recent anatomic\nobservations quite accord with these physiological facts. Taken\ntogether, they convince us that the phronema is undeveloped in the\nnew-born infant; and so we can no more speak in this case of a \"seat of\nthe soul\" than of a \"human spirit\" as a centre of thought, knowledge,\nand consciousness. Hence the destruction of abnormal new-born\ninfants--as the Spartans practised it, for instance, in selecting the\nbravest--cannot rationally be classed as \"murder,\" as is done in even\nmodern legal works. We ought rather to look upon it as a practice of\nadvantage both to the infants destroyed and to the community. As the\nwhole course of embryology is, according to our biogenetic law, an\nabbreviated repetition of the history of the race, we must say the same\nof psychogenesis, or the development of the \"soul\" and its organ--the\nphronema.\n\nComparative psychology comes next in importance to embryology as a\nmeans of studying the ancestral history of the soul. Within the ranks\nof the vertebrates we find to-day a long series of evolutionary stages\nwhich reach up from the lowest acrania and cyclostoma to the fishes\nand dipneusta, from these to the amphibia, and from these again to the\namniota. Among the latter, moreover, the various orders of reptiles and\nbirds on the one hand, and of mammals on the other, show us how the\nhigher psychic powers have been developed step by step from the lower.\nTo this physiological scale corresponds exactly the morphological\ngradation revealed by the comparative anatomy of the brain. The most\ninteresting and important part of this is that which relates to the\nhighest developed class--the mammals; within this class we find the\nsame ever-advancing gradation. At its summit are the primates (man, the\napes, and the half-apes), then the carnivora, a part of the ungulates,\nand the other placentals. A wide interval seems to separate these\nintelligent mammals from the lower placentals, the marsupials and\nmonotremes. We do not find in the latter the high quantitative and\nqualitative development of the phronema which we have in the former;\nyet we find every intermediate stage between the two. The gradual\ndevelopment of the cerebrum and its chief part--the phronema--took\nplace during the Tertiary period, the duration of which is estimated by\nmany recent geologists at from twelve to fifteen (at the least three to\nfive) million years.\n\nAs I have gone somewhat fully, in chapters vi.-ix. of the _Riddle_,\ninto the chief results of the modern study of the brain and its\nradical importance for psychology and the theory of knowledge, I\nneed only refer the reader thereto. There is just one point I may\ntouch here, as it has been attacked with particular vehemence by my\ncritics. I had made several allusions to the works of the distinguished\nEnglish zoologist, Romanes, who had made a careful comparative study\nof mental development in the animal and man, and had continued the\nwork of Darwin. Romanes partly retracted his monistic convictions\nshortly before his death, and adopted mystic religious views. As\nthis conversion was only known at first through one of his friends,\na zealous English theologian [Dr. Gore], it was natural to retain a\ncertain reserve. However, it turned out that there had really been\nin this case (just as in the case of the aged Baer) one of those\ninteresting psychological metamorphoses which I have described in\nchapter vi. of the _Riddle_. Romanes suffered a good deal from illness\nand grief at the loss of friends in his last years. In this condition\nof extreme depression and melancholy he fell under mystic influences\nwhich promised him rest and hope by belief in the supernatural. It\nis hardly necessary to point out to impartial readers that such a\nconversion as this does not shake his earlier monistic views. As in\nsimilar cases where deep emotional disturbance, painful experiences,\nand exuberant hope have clouded the judgment, we must still hold that\nit is the place of the latter, and not of the emotions or of any\nsupernatural revelation, to attain a knowledge of the truth. But for\nsuch attainment it is necessary for the organ of mind, the phronema, to\nbe in a normal condition.[3]\n\nOf all the wonders of life, consciousness may be said to be the\ngreatest and most astounding. It is true that to-day most physiologists\nare agreed that man's consciousness, like all his other mental powers,\nis a function of the brain, and may be reduced to physical and chemical\nprocesses in the cells of the cortex. Nevertheless, some biologists\nstill cling to the metaphysical view that this \"central mystery of\npsychology\" is an insoluble enigma, and not a natural phenomenon.\nIn face of this, I must refer the reader to the monistic theory of\nconsciousness which I have given in chapter x. of the _Riddle_, and\nmust insist that in this case again embryology is the best guide\nto a comprehension of the subject. Sight is next to consciousness,\nin many respects, as one of the wonders of life. The well-known\nembryology of the eye teaches us how sight--the perception of images\nfrom the external world--has been gradually evolved from the simple\nsensitiveness to light of the lower animals, by the development of a\ntransparent lens. In the same way the conscious soul, the internal\nmirror of the mind's own action, has been produced as a new wonder of\nlife out of the unconscious associations in the phronema of our earlier\nvertebrate ancestors.\n\nFrom this thorough and unprejudiced appreciation of the biology of\nthe phronema it follows that the knowledge of truth, the aim of all\nscience, is a natural physiological process, and that it must have\nits organs like all other psychic functions. These organs have been\nrevealed to us so fully in the advance of biology during the last\nhalf-century that we may be said to have a generally satisfactory idea\nof the natural character of their organization and action, though we\nare still far from enjoying a complete anatomical and physiological\ninsight into their details. The most important acquisition we have\nmade is the conviction that all knowledge was originally acquired _a\nposteriori_ and from experience, and that its first sources are the\nimpressions made on our organs of sense. Both these--the peripheral\nsense-organs--and the phronema, or central psychic organ, are subject\nto the law of substance; and the action of the phronema is just as\nreducible to chemical and physical processes as the action of the\norgans of sense.\n\nIn diametrical opposition to our monistic and empirical theory of\nknowledge, the prevailing dualistic metaphysics assumes that our\nknowledge is only partly empirical and _a posteriori_, and is partly\nquite independent of experience and _a priori_, or due to the original\nconstitution of our \"immaterial\" mind. The powerful authority of Kant\nhas lent enormous prestige to this mystic and supernatural view, and\nthe academic philosophers of our time are endeavoring to maintain it.\nA \"return to Kant\" is held to be the only means of salvation for\nphilosophy; in my opinion it should be a return to nature. As a fact,\nthe return to Kant and his famous theory of knowledge is an unfortunate\n\"crab-walk\" on the part of philosophy. Our modern metaphysicians\nregard the brain, as Kant did one hundred and twenty years ago, as a\nmysterious, whitish-gray, pulpy mass, the significance of which as an\ninstrument of the mind is very enigmatic and obscure. But for modern\nbiology the brain is the most wonderful structure in nature, a compound\nof innumerable soul-cells or neurona. These have a most elaborate\nfiner structure, are combined in a vast psychic apparatus by thousands\nof interlacing nerve-fibrils, and are thus fitted to accomplish the\nhighest mental functions.\n\nFIRST TABLE\n\nANTITHESIS OF THE TWO WAYS OF ATTAINING THE TRUTH\n\n MONISTIC THEORY OF KNOWLEDGE \u2502 DUALISTIC THEORY OF KNOWLEDGE\n \u2502\n 1. Knowledge is a natural process,\u2502 1. Knowledge is a supernatural\n not a miracle. \u2502 process, a miracle.\n \u2502\n 2. Knowledge, as a natural \u2502 2. Knowledge, as a transcendental\n process, is subject to the \u2502 process, is not subject\n general law of substance. \u2502 to the law of substance.\n \u2502\n 3. Knowledge is a physiological \u2502 3. Knowledge is not a physiological,\n process, with the brain for \u2502 but a purely spiritual,\n its anatomic organ. \u2502 process.\n \u2502\n 4. The part of the human brain \u2502 4. The part of the human brain\n in which knowledge is \u2502 which seems to act as\n exclusively engendered \u2502 organ of knowledge is\n is a definite and limited \u2502 really only the instrument\n part of the cortex, the \u2502 that allows the spiritual\n phronema. \u2502 process to appear.\n \u2502\n 5. The organ of knowledge, or \u2502 5. The organ of knowledge, or\n the phronema, consists of \u2502 the phronema (the sum of\n the association-centres, \u2502 the association-centres),\n and differs by its special \u2502 is merely a part of the\n histological structure from \u2502 instrument of mind, like\n the neighboring sensory \u2502 the neighboring and correlated\n and motor centres in the \u2502 sensory and motor-centres.\n cortex, and it is in close \u2502\n relation with these. \u2502\n \u2502\n 6. The innumerable cells which \u2502 6. The innumerable phronetal\n make up the phronema--the \u2502 cells, as the microscopic\n phronetal cells--are \u2502 elementary parts of the\n the elementary organs of \u2502 phronema, are, it is true,\n the cognitive process: the \u2502 indispensable instruments\n possibility of knowledge \u2502 of the cognitive process,\n depends on their normal \u2502 but not its real factors--merely\n physical texture and chemical \u2502 finer parts of its\n composition. \u2502 instrument.\n \u2502\n 7. The physical process of \u2502 7. The metaphysical process of\n knowledge consists in the \u2502 knowledge consists in the\n combination or association \u2502 combination or association\n of presentations, the \u2502 of presentations, which are\n first sources of which are \u2502 only partly traceable to\n the impressions transmitted \u2502 sense-impressions, and are\n to the sense-centres. \u2502 partly supersensual, transcendental\n \u2502 processes.\n \u2502\n 8. Hence all knowledge originally \u2502 8. Hence knowledge is of two\n comes from experience, \u2502 kinds: empirical and _a\n by means of the \u2502 posteriori_ knowledge, obtained\n organs of sense; partly \u2502 by experience, and\n directly (direct experience, \u2502 transcendental _a priori_\n observation, and experiment \u2502 knowledge, independent of\n of the present), \u2502 experience. Mathematics\n partly indirectly (historical \u2502 especially belongs to the\n and indirectly transmitted \u2502 latter class, its axioms\n past experiences). \u2502 differing from empirical\n All knowledge (even mathematical) \u2502 truths by their absolute\n is of empirical \u2502 certainty.\n origin and _a posteriori_. \u2502\n\n\n\n\nII\n\nLIFE\n\n Definition of life--Comparison with a flame--Organism and\n organization--Machine theory of life--Organisms without organs:\n monera--Organization and life of the chromacea--Stages of\n organization--Complex organisms--Symbolic organisms--Organic\n compounds--Organisms and inorganic bodies compared in regard\n to matter, form, and function--Crystalloid and colloid\n substances--Life of crystals--Growth of crystals--Waves of\n growth--Metabolism--Catalysis--Fermentation--Biogenesis--Vital\n force--Old and new vitalism--Palavitalism--Antivitalism--Neovitalism.\n\n\nAs the object of this work is the critical study of the wonders of\nlife, and a knowledge of the truth concerning them, we must first\nof all form a clear idea of the meaning of \"life\" and \"wonder,\" or\nmiracle. For thousands of years men have appreciated the difference\nbetween life and death, between living and lifeless bodies; the former\nare called organisms, and the latter known as inorganic bodies.\nBiology--in the widest sense--is the name of the science which treats\nof organisms; we might call the science which deals with the inorganic\n\"abiology,\" abiotik, or anorgik. The chief difference between the two\nprovinces is that organisms accomplish peculiar, periodically repeated,\nand apparently spontaneous movements, which we do not find in inorganic\nmatter. Hence life may be conceived as a special process of movement.\nRecent study has shown that this is always connected with a particular\nchemical substance, _plasm_, and consists essentially in a circulation\nof matter, or _metabolism_. At the same time modern science has shown\nthat the sharp distinction formerly drawn between the organic and the\ninorganic cannot be sustained, but that the two kingdoms are profoundly\nand inseparably united.\n\nOf all the phenomena of inorganic nature with which the life-process\nmay be compared, none is so much like it externally and internally as\nthe flame. This important comparison was made two thousand four hundred\nyears ago by one of the greatest philosophers of the Ionic school,\nHeraclitus of Ephesus--the same thinker who first broached the idea of\nevolution in the two words, _Panta rei_--all things are in a state of\nflux. Heraclitus shrewdly conceived life as a fire, a real process of\ncombustion, and so compared the organism to a torch.\n\nMax Verworn has lately employed this metaphor with great effect in his\nadmirable work on general physiology, and has especially dealt with\nthe comparison of the individual life-form with the familiar butterfly\nshape of the gas-flame. He says:\n\n The comparison of life to a flame is particularly suitable for\n helping us to realize the relation between form and metabolism. The\n butterfly-shape of a gas-flame has a very characteristic outline.\n At the base, immediately above the burner, there is still complete\n darkness; over this is a blue and faintly luminous zone; and over\n this again the bright flame expands on either side like the wings of\n a butterfly. This peculiar form of the flame, with its characteristic\n features, which are permanent, as long as we do not interfere with\n the gas or the environment, is solely due to the fact that the\n grouping of the molecules of the gas and the oxygen at various parts\n of the flame is constant, though the molecules themselves change\n every moment. At the base of the flame the molecules of the gas are\n so thickly pressed that the oxygen necessary for their combustion\n cannot penetrate; hence the darkness we find here. In the bluish\n zone a few molecules of oxygen have combined with the molecules of\n the gas: we have a faint light as the result. But in the body of\n the flame the molecules of the gas are so freely combined with the\n oxygen of the atmosphere that we have a lively combustion. However,\n the exchange of matter (metabolism) between the outpouring gas and\n the surrounding air is so regulated that we always find the same\n molecules in the same quantity at the same spot. Thus we get the\n permanent flame, with all its characteristics. But if we alter the\n circulation by lessening the stream of gas, the shape of the flame\n changes, because now the disposition of the molecules on both sides\n is different. Thus the study of the gas-jet gives us, even in detail,\n the features we find in the structure of the cell.\n\nThe scientific soundness of this metaphor is all the more notable as\nthe phrase, \"the flame of life,\" has long been familiar both in poetry\nand popular parlance.\n\nIn the sense in which science usually employs the word \"organism,\"\nand in which we employ it here, it is equivalent to \"living thing\" or\n\"living body.\" The opposite to it, in the broad sense, is the anorganic\nor inorganic body. Hence the word \"organism\" belongs to physiology,\nand connotes essentially the visible life-activity of the body, its\nmetabolism, nutrition, and reproduction.\n\nHowever, in most organisms we find, when we examine their structure\nclosely, that this consists of various parts, and that these parts\nare put together for the evident purpose of accomplishing the vital\nfunctions. We call them _organs_, and the manner in which they are\ncombined, apparently on a definite plan, is their _organization_. In\nthis respect, we compare the organism to a machine in which some one\nhas similarly combined a number of (lifeless) parts for a definite\npurpose, but according to a preconceived and rationally initiated\ndesign.\n\nThe familiar comparison of an organism to a machine has given rise to\nvery serious errors in regard to the former, and has, of late, been\nmade the base of false dualistic principles. The modern \"machine-theory\nof life\" which is raised thereon demands an intelligent design and\na deliberate constructing engineer for the origin of the organism,\njust as we find in the case of the machine. The organism is then very\nfreely compared to a watch or a locomotive. In order to secure the\nregular working of such a complicated mechanism, it is necessary to\narrange for a perfect co-operation of all its parts, and the slightest\naccident to a single wheel suffices to throw it out of gear. This\nfigure was particularly employed by Louis Agassiz (1858), who saw\n\"an incarnate thought of the Creator\" in every species of animal and\nplant. Of late years it has been much used by Reinke in the support of\nhis theosophic dualism. He described God, or \"the world-soul,\" as the\n\"cosmic intelligence,\" but ascribes to this mystic immaterial being\nthe same attributes that the catechism and the preacher give to the\nCreator of heaven and earth. He compares the human intelligence which\nthe watch-maker has put into the elaborate structure of the watch with\nthe \"cosmic intelligence\" which the Creator has put in the organism,\nand insists that it is impossible to deduce its purposive organization\nfrom its material constituents. In this he entirely overlooks the\nimmense difference between the \"raw material\" in the two cases. The\n\"organs\" of the watch are metallic parts, which fulfil their purpose in\nvirtue only of their physical properties (hardness, elasticity, etc.).\nThe organs of the living organism, on the other hand, perform their\nfunctions chiefly in virtue of their chemical composition. Their soft\nplasma-body is a chemical laboratory, the highly elaborate molecular\nstructure of which is the historical product of countless complicated\nprocesses of heredity and adaptation. This invisible and hypothetical\nmolecular structure must not (as is often done) be confused with the\nreal and microscopically discoverable structure of the plasm, which\nis of great importance in the question of organization. If one is\ndisposed to assume for this molecular structure a simple chemical\nsubstance, a deliberate design, and an \"intelligent natural force\"\nfor cause, one is bound to do the same for powder, and say that the\nmolecules of charcoal, sulphur, and saltpetre have been purposively\ncombined to produce an explosion. It is well known that powder was not\nmade according to a theory, but accidentally discovered in the course\nof experiment. The whole of this favorite machine-theory of life, and\nthe far-reaching dualistic conclusions drawn from it, tumble to pieces\nwhen we study the simplest organisms known to us, the monera; for these\nare really organisms without organs--and without organization!\n\nI endeavored in my _Generelle Morphologie_(1866) to draw the attention\nof biologists to these simplest and lowest organisms which have no\nvisible organization or composition from different organs. I therefore\nproposed to give them the general title of monera. The more I have\nstudied these structureless beings--cells without nuclei!--since that\ntime, the more I have felt their importance in solving the greatest\nquestions of biology--the problem of the origin of life, the nature\nof life, and so on. Unfortunately, these primitive little beings are\nignored or neglected by most biologists to-day. O. Hertwig devotes\none page of his three-hundred-page book on cells and tissues to them;\nhe doubts the existence of cells without nuclei. Reinke, who has\nhimself shown the existence of unnucleated cells among the bacteria\n(_beggiatoa_), does not say a word about their general significance.\nB\u00fctschli, who shares my monistic conception of life, and has given it\nconsiderable support by his own thorough study of plasma-structures\nand the artificial production of them in oil and soap-suds, believes,\nlike many other writers, that the \"composition of even the simplest\nelementary organism from cell-nucleus and protoplasm\" (the primitive\norgans of the cell) is indispensable. These and other writers suppose\nthat the nucleus has been overlooked in the protoplasm of the monera\nI have described. This may be true for one section of them; but\nthey say nothing about the other section, in which the nucleus is\ncertainly lacking. To this class belong the remarkable _chromacea_\n(_phycochromacea_ or _cyanophycea_), and especially the simplest\nforms of these, the _chroococcacea_ (_chroococcus_, _aphanocapsa_,\n_gl\u0153ocapsa_, etc.). These plasmodomous (plasma-forming) monera,\nwhich live at the very frontier of the organic and inorganic worlds,\nare by no means uncommon or particularly difficult to find; on the\ncontrary, they are found everywhere, and are easy to observe. Yet they\nare generally ignored because they do not square with the prevailing\ndogma of the cell.\n\nI ascribe this special significance to the chromacea among all\nthe monera I have instanced because I take them to be the oldest\nphyletically, and the most primitive of all living organisms known\nto us. In particular their very simple forms correspond exactly to\nall the theoretic claims which monistic biology can make as to the\ntransition from the inorganic to the organic. Of the chroococcacea,\nthe chroococcus, gl\u0153ocapsa, etc., are found throughout the world;\nthey form thin, usually bluish-green coats or jelly-like deposits on\ndamp rocks, stones, bark of trees, etc. When a small piece of this\njelly is examined carefully under a powerful microscope, nothing is\nseen but thousands of tiny blue-green globules of plasma, distributed\nirregularly in the common structureless mass. In some species we can\ndetect a thin structureless membrane enclosing the homogeneous particle\nof plasm; its origin can be explained on purely physical principles\nby \"superficial energy\"--like the firmer surface-layer of a drop of\nrain, or of a globule of oil swimming in water. Other species secrete\nhomogeneous jelly-like envelopes--a purely chemical process. In some\nof the chromacea the blue-green coloring matter (_phyocyan_) is stored\nin the surface-layer of the particle of plasm, while the inner part\nis colorless--a sort of \"central body.\" However, the latter is by no\nmeans a real, chemically and morphologically distinct, nucleus. Such a\nthing is completely lacking. The whole life of these simple, motionless\nglobules of plasm is confined to their metabolism (or _plasmodomism_,\nchapter x.) and the resulting growth. When the latter passes a certain\nstage, the homogeneous globule splits into two halves (like a drop\nof quicksilver when it falls). This simplest form of reproduction is\nshared by the chromacea (and the cognate bacteria) with the chromatella\nor chromatophora, the green particles of chlorophyll inside ordinary\nplant-cells; but these are only parts of a cell. Hence no unprejudiced\nobserver can compare these unnucleated and independent granules of\nplasm with real (nucleated) cells, but must conceive them rather\nas _cytodes_. These anatomic and physiological facts may easily be\nobserved in the chromacea, which are found everywhere. The organism\nof the simplest chromacea is really nothing more than a structureless\nglobular particle of plasm; we cannot discover in them any composition\nof different organs (or organella) for definite vital functions. Such a\ncomposition or organization would have no meaning in this case, since\nthe sole vital purpose of these plasma-particles is self-maintenance.\nThis is attained in the simplest fashion for the individual by\nmetabolism; for the species it is effected by self-cleavage, the\nsimplest conceivable form of reproduction.\n\nModern histologists have discovered a very intricate and delicate\nstructure in many of the higher unicellular protists and in many\nof the tissue-cells of the higher animals and plants (such as the\nnerve-cells). They wrongly conclude that this is universal. In my\nopinion, this complication of the structure of the elementary organism\nis always a secondary phenomenon, the slow and gradual result of\ncountless phylogenetic processes of differentiation, initiated by\nadaptation and transmitted to posterity by heredity. The earliest\nancestors of all these elaborate nucleated cells were at first simple,\nunnucleated cytodes, such as we find to-day in the ubiquitous monera.\nWe shall see more about them in the ninth and fifteenth chapters.\n\nNaturally, this lack of a visible histological structure in the\nplasma-globule of the monera does not exclude the possession of an\ninvisible molecular structure. On the contrary, we are bound to assume\nthat there is such a structure, as in all albuminoid compounds, and\nespecially all plasmic bodies. But we also find this elaborate chemical\nstructure in many lifeless bodies; some of these, in fact, show a\nmetabolism similar to that of the simplest organisms. We will return\nsubsequently to this subject of catalysis. Briefly, the only difference\nbetween the simplest chromacea and inorganic bodies that have catalysis\nis in the special form of their metabolism, which we call plasmodomism\n(formation of plasm), or \"carbon-assimilation.\" The mere fact that the\nchromacea assume a globular form is no sign whatever of a morphological\nvital process; drops of quicksilver and other inorganic fluids take the\nsame shape when the individual body is formed under certain conditions.\nWhen a drop of oil falls into a fluid of the same specific gravity with\nwhich it cannot mix (such as a mixture of water and spirits of wine),\nit immediately assumes a globular shape. Inorganic solids usually\ntake the form of crystals instead. Hence the distinctive feature of\nthe simplest organism, the plasma-particles of the monera, is neither\nanatomic structure nor a certain shape, but solely the physiological\nfunction of plasmodomism--a process of chemical synthesis.\n\nThe difference between the monera I have described and any higher\norganism is, I think, greater in every respect than the difference\nbetween the organic monera and the inorganic crystals. Nay, even the\ndifference between the unnucleated monera (as cytodes) and the real\nnucleated cells may fairly be regarded as greater still. Even in the\nsimplest real cell we find the distinction between two different\norganella, or \"cell-organs,\" the internal nucleus and the outer\ncell-body. The _caryoplasm_ of the nucleus discharges the functions\nof reproduction and heredity; the _cytoplasm_ of the cell-body\naccomplishes the metabolism, nutrition, and adaptation. Here we have,\ntherefore, the first, oldest, and most important process of division\nof labor in the elementary organism. In the unicellular protists the\norganization rises in proportion to the differentiation of the various\nparts of the cell; in the tissue-forming histona it rises again in\nproportion to the distribution of work (or ergonomy) among the various\norgans. Darwin has given us in his theory of selection a mechanical\nexplanation of the apparent design and purposiveness in this.\n\nIn order to have a correct monistic conception of organization, it\nis important to distinguish the individuality of the organism in its\nvarious stages of composition. We shall treat this important question,\nabout which there is a good deal of obscurity and contradiction, in a\nspecial chapter (vii.). It suffices for the moment to point out that\nthe unicellular beings (protists) are simple organisms both in regard\nto morphology and physiology. On the other hand, this is only true in\nthe physiological sense of the histona, the tissue-forming animals\nand plants. From the morphological point of view they are made up of\ninnumerable cells, which form the various tissues. These histonal\nindividuals are called sprouts in the plant world and persons in the\nanimal world. At a still higher stage of organization we have the\ntrunk or stem (cormus), which is made up of a number of sprouts or\npersons, like the tree or the coral-stem. In the fixed animal stems the\nassociated individuals have a direct bodily connection, and take their\nfood in common; but in the social aggregations of the higher animals\nit is the ideal link of common interest that unites the individuals,\nas in swarms of bees, colonies of ants, herds of mammals, etc. These\ncommunities are sometimes called \"animal-states.\" Like human polities,\nthey are organisms of a higher type.\n\nHowever, in order to avoid misunderstanding, we must take the word\n\"organism\" in the sense in which most biologists use it--namely, to\ndesignate an individual living thing, the material substratum of which\nis plasm or \"living substance\"--a nitrogenous carbon-compound in a\nsemi-fluid condition. It leads to a good deal of misunderstanding\nwhen separate functions are called organisms, as is done sometimes\nin speaking of the soul or of speech. It would be just as correct to\ncall seeing or running an organism. It is advisable also in scientific\ntreatises to refrain from calling inorganic compounds as such\n\"organisms,\" as, for instance, the sea or the whole earth. Such names,\nhaving a purely symbolical value, may very well be used in poetry. The\nrhythmic wave-movement of the ocean may be regarded as its respiration,\nthe surge as its voice, and so on. Many scientists (like Fechner)\nconceive the whole earth with all its organic and inorganic contents\nas a gigantic organism, whose countless organs have been arranged\nin an orderly whole by the world-reason (God). In the same way the\nphysiologist, Preyer, regards the glowing heavenly bodies as \"gigantic\norganisms, whose breath is, perhaps, the glowing vapor of iron, whose\nblood is liquid metal, and whose food may be meteorites.\" The danger of\nthis poetic application of the metaphorical sense of organism is very\nwell seen in this instance, as Preyer builds on it a quite untenable\nhypothesis of the origin of life (see chapter xv.).\n\nIn the wider sense the word \"organic\" has long been used in chemistry\nas an antithesis to inorganic. By organic chemistry is generally\nunderstood the chemistry of the compounds of carbon, that element being\ndistinguished from all the others (some seventy-eight in number) by\nvery important properties. It has, in the first place, the property of\nentering into an immense variety of combinations with other elements,\nand especially of uniting with oxygen, hydrogen, nitrogen, and sulphur\nto form the most complicated albuminoids (see the _Riddle_, chapter\nxiv.). Carbon is a biogenetic element of the first importance, as I\nexplained in my carbon-theory in 1866. It might even be called \"the\ncreator of the organic world.\" At first these organogenetic compounds\ndo not appear in the organism in organized form--that is to say, they\nare not yet distributed into organs with definite purposes. Such\norganization is a result, not the cause, of the life-process.\n\nI have already shown in the fourteenth chapter of the _Riddle_(and at\ngreater length in the fifteenth chapter of my _History of Creation_)\nthat the belief in the essential unity of nature, or the monism of\nthe cosmos, is of the greatest importance for our whole system. I\ngave a very thorough justification of this cosmic monism in 1866. In\nthe fifth chapter of the _Generelle Morphologie_ I considered the\nrelation of the organic to the inorganic in every respect, pointing\nout the differences between them on the one hand, and their points of\nagreement in matter, form, and force on the other. N\u00e4geli some time\nafterwards declared similarly for the unity of nature in his able\n_Mechanisch-physiologische Begr\u00fcndung_ _der Abstammungslehre_(1884).\nWilhelm Ostwald has recently done the same, from the monistic point of\nview of his system of energy, in his _Naturphilosophie_, especially in\nthe sixteenth chapter. Without being acquainted with my earlier work,\nhe has impartially compared the physico-chemical processes in the\norganic and inorganic worlds, partly adducing the same illustrations\nfrom the instructive field of crystallization. He came to the same\nmonistic conclusions that I reached thirty-six years ago. As most\nbiologists continue to ignore them, and as, especially, modern vitalism\nthrusts these inconvenient facts out of sight, I will give a brief\nsummary once more of the chief points as regards the matter, form, and\nforces of bodies.\n\nChemical analysis shows that there are no elements present in organisms\nthat are not found in inorganic bodies. The number of elements that\ncannot be further analyzed is now put at seventy-eight; but of these\nonly the five organogenetic elements already mentioned which combine\nto form plasm--carbon, oxygen, hydrogen, nitrogen, and sulphur--are\nfound invariably in living things. With these are generally (but not\nalways) associated five other elements--phosphor, potassium, calcium,\nmagnesium, and iron. Other elements may also be found in organisms; but\nthere is not a single biological element that is not also found in the\ninorganic world. Hence the distinctive features which separate the one\nfrom the other can be sought only in some special form of combination\nof the elements. And it is carbon especially, the chief organic\nelement, that by its peculiar affinity enters into the most diverse and\ncomplicated combinations with other elements, and produces the most\nimportant of all substances, the albuminoids, at the head of which is\nthe living plasm (_cf._ chapter vi.).\n\nAn indispensable condition of the circulation of matter (metabolism)\nwhich we call life is the physical process of osmosis, which is\nconnected with the variations in the quantity of water in the living\nsubstance and its power of diffusion. The plasm, which is of a spongy\nor viscous consistency, can take in dissolved matter from without\n(endosmosis) and eject matter from within (exosmosis). This absorptive\nproperty (or \"imbibition-energy\") of the plasm is connected with the\ncolloidal character of the albuminoids. As Graham has shown, we may\ndivide all soluble substances into two groups in respect of their\ndiosmosis--crystalloids and colloids. Crystalloids (such as soluble\nsalt and sugar) pass more easily into water through a porous wall\nthan colloids (such as albumen, glue, gum, caramel). Hence we can\neasily separate by dialysis two bodies of different groups which are\nmixed in a solution. For this we need a flat bottle with side walls\nof india-rubber and bottom of parchment. If we let this vessel float\nin a large one containing plenty of water, and pour a mixture of\ndissolved gum and sugar into the inner vessel, after a time nearly\nall the sugar passes through the parchment into the water, and an\nalmost pure solution of gum remains in the bottle. This process of\ndiffusion, or osmosis, plays a most important part in the life of all\norganisms; but it is by no means peculiar to the living substance,\nany more than the absorptive or viscous condition is. We may even\nhave one and the same substance--either organic or inorganic--in both\nconditions, as crystal or as colloid. Albumen, which usually seems\nto be colloidal, forms hexagonal crystals in many plant-cells (for\ninstance, in the aleuron-granules of the endosperm), and tetrahedric\nh\u0153moglobin-crystals in many animal-cells (as in the blood corpuscles\nof mammals). These albuminoid crystals are distinguished by their\ncapacity for absorbing a considerable quantity of water without losing\ntheir shape. On the other hand, mineral silicon, which appears as\nquartz in an immense variety (more than one hundred and sixty) of\ncrystalline forms, is capable in certain circumstances (as metasilicon)\nof becoming colloidal and forming jelly-like masses of glue. This\nfact is the more interesting because silicium behaves in other ways\nvery like carbon, is quadrivalent like it, and forms very similar\ncombinations. Amorphous (or non-crystalline) silicium (a brown powder)\nstands in relation to the black metallic silicon-crystals just as\namorphous carbon does to graphite-crystals. There are other substances\nthat may be either crystalloid or colloid in different circumstances.\nHence, however important colloidal structure may be for the plasm and\nits metabolism, it can by no means be advanced as a distinctive feature\nof living matter.\n\nNor is it possible to assign an absolute distinction between the\norganic and the inorganic in respect of morphology any more than of\nchemistry. The instructive monera once more form a connecting bridge\nbetween the two realms. This is true both of the internal structure\nand the outward form of both classes of bodies--of their individuality\n(chapter vii.) and their type (chapter viii.). Inorganic crystals\ncorrespond morphologically to the simplest (unnucleated) forms of the\norganic cells. It is true that the great majority of organisms seem to\nbe conspicuously different from inorganic bodies by the mere fact that\nthey are made up of many different parts which they use as organs for\ndefinite purposes of life. But in the case of the monera there is no\nsuch organization. In the simplest cases (chromacea, bacteria) they are\nstructureless, globular, discoid, or rod-shaped plasmic individuals,\nwhich accomplish their peculiar vital function (simple growth and\nsubdivision) solely by means of their chemical constitution, or their\ninvisible molecular structure.\n\nThe comparison of cells with crystals was made in 1838 by the founders\nof the cell-theory, Schleiden and Schwann. It has been much criticised\nby recent cytologists, and does not hold in all respects. Still it is\nof importance, as the crystal is the most perfect form of inorganic\nindividuality, has a definite internal structure and outward form,\nand obtains these by a regular growth. The external form of crystals\nis prismatic, and bounded by straight surfaces which cut each other\nat certain angles. But the same form is seen in the skeletons of many\nof the protists, especially the flinty shells of the diatomes and\nradiolaria; their silicious coverings lend themselves to mathematical\ndetermination just as well as the inorganic crystals. Midway between\nthe organic plasma-products and inorganic crystals we have the\n_bio-crystals_, which are formed by the united plastic action of the\nplasm and the mineral matter--for instance, the crystalline flint and\nchalk skeletons of many of the sponges, corals, etc. Further, by the\norderly association of a number of crystals we get compound crystal\ngroups, which may be compared to the communities of protists--for\ninstance, the branching ice-flowers and ice-trees on the frozen\nwindow. To this regular external form of the crystal corresponds a\ndefinite internal structure which shows itself in their cleavage, their\nstratified build, their polar axes, etc.\n\nIf we do not restrict the term \"life\" to organisms properly so-called,\nand take it only as a function of plasm, we may speak in a broader\nsense of the life of crystals. This is seen especially in their\ngrowth, the phenomenon which Baer regarded as the chief character of\nall individual development. When a crystal is formed in a matrix,\nthis is done by attracting homogeneous particles. When two different\nsubstances, A and B, are dissolved in a mixed and saturated solution,\nand a crystal of A is put in the mixture, only A is crystallized out of\nit, not B; on the other hand, if a crystal of B is put in, A remains in\nsolution and B alone assumes the solid crystalline form. We may, in\na certain sense, call this choice _assimilation_. In many crystals we\ncan detect internally an interaction of their parts. When we cut off\nan angle in a forming crystal, the opposite angle is only imperfectly\nformed. A more important difference between the growth of crystals and\nmonera is that the former only grow by _apposition_, or the deposit of\nfresh solid matter at their surface; while the monera grow, like all\ncells, by _intussusception_, or the taking of new matter into their\ninterior. But this difference is easily explained by their difference\nin consistency, the crystal being solid and the plasm semi-fluid.\nMoreover, the difference is not absolute; there are intermediary\nstages between apposition and intussusception. A colloid globule\nsuspended in a salt solution in which it is not dissolved may grow by\nintussusception.\n\nIt was once the custom to restrict sensation and movement to animals,\nbut they are now recognized to be present in nearly all living matter.\nThey are, in fact, not altogether lacking in crystals, as the molecules\nmove in crystallization in definite directions, and unite according to\nfixed laws; they must, therefore, also possess sensation, as we could\nnot otherwise understand the attraction of the homogeneous particles.\nWe find in crystallization, as in every chemical process, certain\nmovements which are unintelligible without sensation--unconscious\nsensation, of course. In this respect, also, then, the growth of all\nbodies follows the same laws (_cf._ chapters xiii. and xv.).\n\nThe growth of a crystal is restricted like the growth of a moneron or\nof any cell. If the limit is passed and the conditions remain favorable\nto growth, we find an instance of that excessive or _transgressive_\ngrowth which we call reproduction in the case of living individuals.\nBut we find just the same kind of extension in the inorganic crystal.\nEvery crystal grows in a supersaturated medium only up to a definite\nsize, which is determined by its chemical-molecular constitution. When\nthis limit is reached a number of small crystals appear on the large\none. Ostwald, who has made a thorough comparison of the process of\ngrowth in crystals and monera, especially notices the striking analogy\nbetween a bacterium (a plasmophagous moneron) growing and multiplying\nin its nutritive fluid and a crystal in its matrix. When the water\nslowly evaporates from a supersaturated solution of Glauber-salt, not\nonly does a crystal slowly grow in it, but several young crystals\nappear on it. The analogy with the bacterium multiplying in its\nnutritive fluid can even be followed as far as its permanent forms or\n\"spores.\" This quiescent form is assumed by the bacterium if its supply\nof food is exhausted; if fresh food is added, the multiplication by\ncleavage begins again. In the same way the crystals of Glauber-salt\nbegin to decay when the solution is evaporated; they lose their crystal\nwater, but not their power of multiplication. Even the amorphous powder\nof the salt causes again the formation of new watery crystals when put\nin a supersaturated solution. But the powder loses this property when\nit is heated, just as the dormant forms (or spores) of the bacteria\nlose their power of germination.\n\nThe exhaustive comparison of the growth of crystals and monera (as the\nsimplest forms of unnucleated cells) is important, because it shows\nthe possibility of tracing the vital function of reproduction--which\nhad usually been regarded as a quite special \"wonder of life\"--to\npurely physical conditions. The division of the growing individual\ninto several young ones must necessarily take place when the natural\nlimit of growth has been passed, and when the chemical composition of\nthe growing body and the cohesion of its molecules allow no further\nenlargement by the assumption of new matter. In order to illustrate\nthe limit of this transgressive growth by a simple physical example,\nOstwald imagines a ball placed in a small flat basin, built up high on\none side. The ball is in a state of equilibrium in the basin; when it\nis lightly pushed aside it always returns to its original position.\nBut when the push goes beyond a certain point, and the ball is thrust\nover the side of the basin, the balance is lost; the ball does not\nreturn, but falls to the ground. The crystal behaves just in the same\nway in a supersaturated solution when it exercises its power of forming\nnew crystals; and it is just the same with the bacterium growing in a\nnutritive fluid when it passes the limit of its volume of growth, and\ndivides into two individuals.\n\nAs we can find no morphological and little physiological difference\nbetween the living and non-living, we must look upon metabolism as\nthe chief characteristic of organic life. This process causes the\nconversion of food into plasm; it is determined by the vital force\nitself, and is the formation of new living matter. It thus effects\nthe nutrition and growth of the living being, and therefore its\nreproduction, which is merely transgressive growth. As I shall describe\nthis metabolism fully in the tenth chapter, I will do no more here\nthan emphasize the fact that this vital process also has analogies in\ninorganic chemistry, in the curious process of catalysis, especially\nthat form of it which we call fermentation.\n\nThe distinguished chemist Berzelius discovered in 1810 the\nremarkable fact that certain bodies, by their mere presence, apart\nfrom their chemical affinity, set other bodies in decomposition or\ncomposition without being themselves affected. Thus, for instance,\nsulphuric acid changes the starch in sugar without undergoing any\nalteration itself. Finely ground platinum brought in contact with\nhydrogen-superoxide divides it into hydrogen and oxygen. Berzelius\ncalled this process _catalysis_; Mitscherlich, who discovered the\ncause of it to be the peculiar surface-action of many bodies, gave\nit the name of \"contact-action.\" It was afterwards discovered that\ncatalysis of this kind is very general, and that a special form of\nit--fermentation--plays an important part in the life of organisms.\n\nThis special form of contact-action which we call fermentation is\nalways effected by catalytic bodies of the albuminoid class, and,\nin fact, of the group of non-coagulable proteins which are known as\npeptones. They have--in however small a quantity--the capacity to\nthrow into decomposition large masses of organic matter (in the form\nof yeast, putrid matter, etc.) without themselves taking part in the\ndecomposition. When these ferments are free and unorganized they\nare called enzyma, in opposition to organized ferments (bacteria,\nyeast-fungi, etc.); though the catalytic action of the latter\nalso consists essentially in the production of enzyma. The recent\ninvestigations of Verworn, Hofmeister, Ostwald, etc., have shown that\nthese catalyses play everywhere an important part in the life of the\nplasm. Many recent chemists and physiologists are of opinion that\nplasm is a _colloid catalysator_, and that all the varied activities\nof life are connected with this fundamental vital chemistry. Thus\nFranz Hofmeister (1901) says in his excellent work on _The Chemical\nOrganization of the Cell_:\n\n The belief that the agents of the chemical transformation in the\n cell are catalysators of a colloid nature is in complete accord\n with other facts that have been directly ascertained. What else are\n the chemists' ferments but colloid catalysators? The idea that the\n ferments are the essential chemical agency in the cell is calculated\n to meet the difficulty which arises from the smallness of the cell\n in appreciating its chemical processes. However large we suppose the\n colloid ferment molecules to be, there is room for millions of them\n in the smallest cell.\n\nIn the same way Ostwald attributes the greatest significance to\ncatalysis in connection with the vital processes, and seeks to explain\nthem on his theory of energy by reference to the duration of chemical\nprocesses. In the discourse \"On Catalysis\" that he delivered at Hamburg\nin 1901 he says:\n\n We must recognize the enzyma as catalysators that arise in the\n organism during the life of the cells, and by their action relieve\n the living being of the greater part of its duties. Not only are\n digestion and assimilation controlled by enzyma from first to last,\n but the fundamental vital action of most organisms, the production\n of the necessary chemical energy by combustion at the expense of\n the oxygen in the air, takes place with the explicit co-operation\n of enzyma, and would be impossible without them. Free oxygen is, as\n is well known, a very inert body at the temperature of the living\n body, and the maintenance of life would be impossible without some\n acceleration of its rate of reaction.\n\nIn his further observations on catalysis and metabolism he says that\nthey are both equally subject to the physico-chemical laws of energy.\n\nMax Verworn has given us a very searching analysis of the molecular\nprocess in the catalytic aspect of metabolism in his _Biogen\nHypothesis_ (1903), \"a critical and experimental study of the processes\nin living matter.\" He simplifies the catalytic theory of the enzyma\nby tracing all the phenomena of life to the catalytic metabolism\nof one single chemical compound, the plasm, and regards its active\nmolecules, the biogens, as the ultimate chemical factors of the vital\nprocess. While the enzyma hypothesis assumes that there are in each\ncell a great number of different enzyma which are all co-ordinated,\nand each of which only performs its little special work, the biogen\nhypothesis deduces all the vital phenomena from one compound, the\nbiogenetic plasm; and thus the biogen molecules, which increase by\ndivision into parts, are the sole factors of biological catalysis.\nVerworn also points out the analogy between this enzymatic process of\nmetabolism and the inorganic processes of catalysis--for instance,\nin the manufacture of English sulphuric acid. A small and constant\nquantity of nitromuriatic acid, with the aid of air and water, converts\nan unlimited mass of sulphuretted acid into sulphuric acid without\nbeing changed itself; the molecule of the nitromuriatic acid breaks\nup steadily by the giving-off of oxygen, and is then restored by the\nassumption of oxygen.\n\nThe manifold and changeful phenomena of life and their sudden\nextinction at death seem to every thoughtful man to be something\nso wonderful and so different from all the changes in inorganic\nnature that from the very beginning of biological philosophy special\nforces were assumed to explain it. This was particularly due to\nthe remarkable, orderly structure of the organism and the apparent\npurposiveness of the vital processes. Hence, in earlier days a\nspecial organic force (_arch\u00e6us insitus_) was assumed, controlling\nthe individual life and pressing the \"raw forces\" of inorganic matter\ninto its service. In the same way a special formative impulse was\nsupposed to preside over the wonderful processes of development. When\nphysiology began to win its independence, about the middle of the\neighteenth century, it explained the peculiar features of organic life\nby a specific vital force. The idea was generally received, and Louis\nDumas endeavored thoroughly to establish it at the beginning of the\nnineteenth century (_cf._ chapter iii. of the _Riddle_).\n\nAs the theory of a vital force, or vitalism, plays an important part\nin the study of the wonders of life, has undergone the most curious\nmodifications in the course of the nineteenth century, and has been\nlately revived with great force, we must give a short account of it\nin its various forms. The phrase can be interpreted in a monistic\nsense, if we understand by it the sum of the forms of energy which\nare especially distinctive of the organism, particularly metabolism\nand heredity. In this we pass no opinion on their nature, and do\nnot say that they are specifically different from the forces of\ninorganic nature. We might call this monistic conception \"physical\nvitalism.\" However, the usual metaphysical vitalism affirms in a\nthoroughly dualistic sense that the vital force is a teleological and\nsuper-mechanical principle, is essentially different from the ordinary\nforces of nature, and of a transcendental character. The special form\nin which this theory of a supernatural vital force has been presented\nfor the last twenty years is often called Neovitalism; we might call\nthe older form, by contrast, Palavitalism.\n\nThe older idea of the vital force as a special energy could very well\nbe accepted in the first third of the nineteenth century, and in the\neighteenth, because the physiology of the time was destitute of the\nmost important aids to the founding of a mechanical theory. There was\nthen no such thing as the cell-theory or as physiological chemistry;\nontogeny and paleontology were still in their cradles. Lamarck's\ntheory of descent (1809) had been done to death, like his fundamental\nprinciple: \"Life is only an elaborate physical phenomenon.\" Hence we\ncan easily understand how physiologists acquiesced in the vitalist\nhypothesis up to 1833, and supposed the wonders of life to be enigmatic\nphenomena that escaped physical explanation.\n\nBut the position of Palavitalism changed in the second third of the\nnineteenth century. In 1833 appeared Johannes M\u00fcller's classical\n_Manual of Human Physiology_, in which the great biologist not only\nmade a comparative study of the vital phenomena in man and the animals,\nbut sought to provide a sound basis for it in all its sections by his\nown observations and experiments. It is true that M\u00fcller retained\nto the last (1858) the current idea of a vital force, as the supreme\nregulator of all the vital activities. However, he did not regard it\nas a metaphysical principle (like Haller, Kant, and their followers),\nbut as a natural force, subject, like all others, to fixed chemical\nand physical laws, and subordinate to the whole. In his comprehensive\nstudy of every single vital function--the organs of sense and the\nnervous system, metabolism and the action of the heart, speech and\nreproduction--M\u00fcller endeavored above all to establish, by close\nobservation of the facts and careful experiments, the regularity\nof the phenomena, and to explain their development by a comparison\nof the higher and lower forms. Hence Johannes M\u00fcller is wrongly\ndescribed--as he has been of late--as a vitalist; he was rather the\nfirst physiologist to provide a physical foundation for the current\nmetaphysical vitalism. He really gives an indirect proof of the reverse\ntheory, as E. Dubois-Reymond rightly observed in his brilliant memorial\nspeech. In the same way Schleiden (1843) cut the ground from under\nvitalism in botany. By his cell-theory (1838) he showed the unity of\nthe multicellular organism to be the resultant of the functions of all\nthe cells which compose it.\n\nThe physical explanation of the vital processes and the rejection\nof Palavitalism were general in the last third of the nineteenth\ncentury. This was due most of all to the great advance in experimental\nphysiology, which Carl Ludwig and Felix Bernard led as regards the\nanimal body, and Julius Sachs and Wilhelm Preyer for the plant. While\nthese and other physiologists used the remarkable results of modern\nphysics and chemistry in the experimental study of the vital functions,\nand sought to determine their complicated course in terms of mass and\nweight and formulate their discoveries as mathematically as possible,\nthey brought a great number of the wonders of life under the same\nfixed laws that were recognized in the physics and chemistry of the\ninorganic world. On the other hand, vitalism met with a powerful\nopponent in Charles Darwin, who solved, by his theory of selection,\none of the most obscure biological problems, the constantly repeated\nquestion: How can we give a mechanical explanation of the orderly\nstructures of the living being? How was this ingenious machine of the\nanimal or plant body unconsciously produced by natural means, without\nsupposing that some intelligent artificer or creator had deliberately\ndesigned and produced it?\n\nThe further development of Darwin's theory of selection in the last\nfour decades, and the increasing support which has been given to\nthe theory of descent in the great advance of ontogeny, phylogeny,\ncomparative anatomy, and physiology, did much to establish the monistic\nconception of life. It took the shape more and more of a definite\nanti-vitalism. Hence it is strange to find that in the course of the\nlast twenty years the old vitalism that everybody had thought dead has\nlifted up its head once more, though in a new and modified form.[4]\nThis modern vitalism comprises two essentially different tendencies.\n\nThe partisans of the modern vital force are divided into two groups,\nwhich may be designated the sceptical and the dogmatic. Sceptical\nNeovitalism was first formulated by Bunge, of Basle (1887), in the\nintroduction to his _Manual of Physiological Chemistry_. While he\ngranted the possibility of a full explanation of one part of the vital\nphenomena by mechanical causes, or the physical and chemical forces\nof lifeless nature, he rejected it for the other half, especially for\npsychic activities. He insists that the latter cannot be explained\nmechanically, and that there is nothing analogous to them in inorganic\nnature; only a supra-mechanical vital force can produce them, and this\nis transcendental and beyond the range of scientific inquiry. Much the\nsame was said later by Rindfleisch (1888), more recently by Richard\nNeumeister in his _Studies of the Nature of Vital Phenomena_ (1903),\nand by Oscar Hertwig in the lecture on \"The Development of Biology in\nthe Nineteenth Century,\" which he delivered at Aachen in 1900.\n\nThis sceptical Neovitalism is far surpassed by the dogmatic system,\nthe chief actual representatives of which are the botanist Johannes\nReinke and the metaphysician Hans Driesch. The vitalist writings of the\nlatter, which are devoid of any grasp of historical development, have\ngained a certain vogue through the extraordinary arrogance of their\nauthor and the obscurity of his mystic and contradictory speculations.\nReinke, on the other hand, has presented his transcendental dualism\nin clever and attractive form in two works which deserve notice on\naccount of their consistent dualism. In the first of these, _The World\nas Reality_ (1899), Reinke gives us \"the outline of a scientific theory\nof the universe.\" The second work (1901) has the title, _Introduction\nto Theoretical Biology_. The two works have the same relation to each\nother as my _Riddle of the Universe_ and the present supplementary\nvolume. As our philosophic convictions are diametrically opposed in the\nmain issues, and as we both think ourselves consistent in developing\nthem, the comparison of them is not without interest in the great\nstruggle of beliefs. Reinke is an avowed supporter of dualism, theism,\nand teleology. He reduces all the phenomena of life to a supernatural\nmiracle.\n\nSECOND TABLE\n\nANTITHESIS OF THE MONISTIC AND DUALISTIC THEORIES OF ORGANIC LIFE\n\n MONISTIC THEORY OF LIFE \u2502 DUALISTIC THEORY OF LIFE\n (Biophysics) \u2502 (Vitalism)\n \u2502\n 1. The phenomena of life are \u2502 1. The phenomena of life are\n merely functions of plasm, \u2502 wholly or partly independent\n determined by the physical, \u2502 of the plasm, and\n chemical, and morphological \u2502 determined by a special\n character of the \u2502 immaterial force, the vital\n living matter. \u2502 force (_vis vitalis_).\n \u2502\n 2. The energy of the plasm (as \u2502 2. The energy of the plasm is\n the sum-total of the forces \u2502 wholly or partly subject\n which are connected with \u2502 to the immaterial vital\n the living matter) is subject \u2502 force, which controls and\n to the general laws of \u2502 directs the physical and\n physics and chemistry. \u2502 chemical forces of the\n \u2502 living matter.\n \u2502\n 3. The obvious regularity of the \u2502 3. The general regularity in the\n vital processes and the \u2502 organization and in the\n organization they produce \u2502 vital processes it accomplishes\n are the outcome of natural \u2502 is the outcome of\n evolution; their physiological \u2502 conscious creation; it can\n factors (heredity \u2502 only be explained by intelligent\n and adaptation) are subject \u2502 immaterial forces\n to the law of substance. \u2502 which are not subject to\n \u2502 the law of substance.\n \u2502\n 4. All the various functions \u2502 4. All the various functions of\n have thus been mechanically \u2502 organisms have been produced\n produced, orderly \u2502 by design, the\n structures having been \u2502 historical evolution (or\n created by adaptation and \u2502 phyletic transformation)\n transmitted to posterity \u2502 being directed to a preconceived\n by heredity. \u2502 ideal end.\n \u2502\n 5. Nutrition is a physico-chemical \u2502 5. Nutrition is an inexplicable\n process, the metabolism \u2502 miracle of life, and cannot\n of which has an \u2502 be understood by chemical\n analogy in inorganic catalysis. \u2502 and physical processes.\n \u2502\n 6. Reproduction is a mechanical \u2502 6. Reproduction is an inexplicable\n consequence of transgressive \u2502 miracle of life,\n growth, analogous \u2502 without any analogy in\n to the elective multiplication \u2502 inorganic nature.\n of crystals. \u2502\n \u2502\n 7. The movement of organisms \u2502 7. The movement of organisms\n is, in every form, not \u2502 is an inexplicable metaphysical\n essentially different from \u2502 miracle of life,\n the movements of inorganic \u2502 specifically different from\n dynamos. \u2502 all inorganic movements.\n \u2502\n 8. Sensation is a general form \u2502 8. The sensation of organisms\n of the energy of substance, \u2502 can only be explained by\n not specifically different \u2502 ascribing a soul to them,\n in sensitive organisms and \u2502 an immaterial, immortal\n irritable inorganic objects \u2502 being that only dwells for\n (such as powder, dynamite). \u2502 a time in the body. After\n There is no such \u2502 death this spirit lives an\n thing as an immaterial \u2502 independent life.\n soul. \u2502\n\n\n\n\nIII\n\nMIRACLES\n\n Miracle and natural law--Belief in miracles of savages (fetichism),\n of semi-civilized (idolatry), of civilized (theism), and of\n educated people (dualism)--Religious belief in miracles--Apostles'\n Creed--Article relating to creation--Article relating to\n redemption--Article relating to immortality--Philosophic belief in\n miracles--Academic thinkers and Free-thinkers--Dualism of Plato\n and Kant--Belief in miracles in the nineteenth century, in modern\n metaphysics, theology, and politics.\n\n\nIn ordinary parlance the word \"miracle\" means a number of different\nthings. We say a phenomenon is miraculous or wonderful[5] when we\ncannot explain it and trace its causes. But we say a natural object\nor a work of art is wonderful when it is unusually beautiful and\nimposing--when it passes the ordinary limits of our experience. In this\nwork I do not take the word in this relative sense, but in the absolute\nsense in which a phenomenon is said to transcend the limits of natural\nlaw and lie beyond the range of rational explanation. In this sense\nit means the same as \"supernatural\" or \"transcendental.\" We can know\nnatural phenomena by our reason and bring them within our cognizance.\nThe miraculous can only be accepted on faith.\n\nThe belief in supernatural miracles is in contradiction to pure reason,\nwhich lays the foundations of all science. Kant, who won so great a\nvogue for the term \"pure reason,\" understood by this originally \"reason\nas independent of experience.\" The phrase was used in a narrower sense\nsubsequently to express independence of dogma and prejudice, as the\nbase of pure and unprejudiced science. In this sense we oppose pure\nreason to superstition.\n\nI have dealt in the sixteenth chapter of the _Riddle_ with the\nimportant question of the relations of knowledge and faith. But I\nmust return to the subject here, as what I said has given rise to a\ngood deal of misunderstanding and criticism. I by no means claimed,\nas my opponents allege, to \"know everything,\" or to have solved every\nproblem. In fact, I said repeatedly that there are narrow limits to\nour knowledge, and always will be. I had also expressly stated that\nthe irresistible impulse to learn in the intelligent man, or reason's\nconstant demand to know causes, presses us to fill up the gaps in our\nknowledge by faith. But I had at the same time pointed out the contrast\nbetween scientific (natural) and religious (supernatural) faith. The\none leads us to form hypotheses and theories; the other ends in myths\nand superstition. Scientific faith fills the gaps in our knowledge\nof natural law with temporary hypotheses; but mystic religious faith\ncontradicts natural law, and transcends its limits in the form of a\nbelief in miracles.\n\nThe great triumph of the progress of science in the nineteenth century,\nits theoretical value in the formation of a rational philosophy\nof life, and its practical value on the various sides of modern\ncivilization, consist, above all, in the absolute recognition of fixed\nnatural laws. That relation of things to each other, which we call\ncausation, makes it possible for us to understand and explain facts.\nWe feel that our thirst for a knowledge of the causes of things is\ncontented when science points out the \"sufficient reason\" of them. In\nthe whole province of inorganic cosmology natural law is now generally\nrecognized to be all-powerful; in astronomy, geology, physics,\nand chemistry all phenomena are reduced to fixed laws, and in the\nlong-run to the all-embracing law of substance, the great law of the\nconservation of matter and force (_Riddle_, chapter xii.).\n\nIt is otherwise in biology, or the organic section of cosmology. Here\nwe still find miracles set up in opposition to the law of substance,\nand the transgression of natural laws by supernatural forces. The\nbelief in miracles of this kind, which pure reason calls superstition,\nis still very wide-spread--much more prevalent than is usually thought.\nFor my part, I hold that superstition and unreason are the worst\nenemies of the human race, while science and reason are its greatest\nfriends. Hence it is our duty and task to attack the belief in miracles\nwherever we find it, in the interest of the race. We have to prove that\nthe reign of natural law extends over the whole world of phenomena\nas far as we can reach it. A general survey of the history of faith\non the one hand and of science on the other clearly shows that the\nadvance of the latter has always been accompanied by an increasing\nknowledge of fixed natural laws and the shrinking of superstition\ninto an ever-lessening area. To-day we convince ourselves of this\nby an impartial examination of mental culture at the various stages\nof civilization. For this purpose I take the four chief stages of\nmental development which Fritz Schultze has given in his _Physiology\nof Uncivilized Races_, and Alexander Sutherland in his work, _On the\nOrigin and Growth of the Moral Instinct_: 1, savages; 2, barbarians; 3,\ncivilized races; 4, educated races (_cf._ chapter i.).\n\nThe mental life of savages rises little above that of the higher\nmammals, especially the apes, with which they are genealogically\nconnected. Their whole interest is restricted to the physiological\nfunctions of nutrition and reproduction, or the satisfaction of hunger\nand thirst in the crudest animal fashion. Without fixed habitation,\nconstantly struggling for existence, they live on the raw produce of\nnature--fruits, the roots of wild plants, and the animals they fish\nin the water or catch on land. Their intelligence moves within the\nnarrowest bounds, and one can no more (or no less) speak of their\nreason than of that of the more intelligent animals. Of art and science\nthere is no question. Their impulse to discover causes is satisfied\nwith the simplest association of phenomena which have a merely external\nconnection, but no intimate relation to each other. Thus arises\ntheir _fetichism_, that irrational trust in fetiches which Fritz\nSchultze has traced to four distinct causes: their false estimate of\nthe value of an object, their anthropomorphic conception of nature,\nthe imperfect association of their ideas, and the strength of their\nemotions, especially hope and fear. Any favorite object, a stone or\na bone, may work miracles as a fetich and exercise all kinds of good\nor evil influence, and is therefore honored, feared, and worshipped.\nAt first the worship was paid to the invisible spirit that dwelt in\nthe particular object; but it was often transferred afterwards to the\ndead object itself. Among the different savage races the belief in\nfetiches presents a number of stages, corresponding to the beginnings\nof reason. The lowest stage is found in the lowest races, such as the\nVeddahs of Ceylon, the Andaman Islanders, Bushmen, and Akkas (of New\nGuinea). A somewhat higher stage is met in the middle races (Australian\nnegroes, Tasmanians, Hottentots, and Tierra del Fuegians); and a still\nhigher intellectual development is shown by the next group (most of\nthe Indians of North and South America, the aboriginal inhabitants\nof India, etc.). Modern comparative ethnography and evolution and\nprehistoric and anthropological research have shown us that our own\nancestors, ten thousand and more years ago, were (like the prehistoric\nancestors of all races of men) savages, and that their earliest belief\nin miracles was a crude fetichism.\n\nBy barbarians we understand the races that are found between savage\nand civilized peoples. They show the first beginnings of civilization,\nand are superior to savages chiefly in the possession of agriculture\nand the keeping of cattle. They make a provident use of the productive\nforces of organic nature, artificially produce large quantities of\nfood, and are thus enabled by the abundance of food to turn their minds\nto other interests. We find that they have the rudiments of art and\nscience. Their religion does not at first rise much above fetichism,\nbut soon reaches the stage of animism, lifeless objects in nature\nbeing credited with souls. Worship is no longer paid to favorite dead\nobjects (stones, bones, etc.), but generally to living things, trees\nand animals, and especially to images of gods which have the form\nof animals or men, and are believed to possess souls. As demons or\nspirits, these have a great influence on the fortunes of men. At first\nthis soul is conceived to be purely material; it disappears at the\ndeath of the body and lives apart. As the breathing and the beat of the\npulse and heart cease when a man dies, the seat of the soul is thought\nto be the lungs, heart, or some other part of the body. The idea of the\nimmortality of the soul takes on innumerable forms among them, like the\nbelief in the miracles which are worked by the gods, demons, spirits,\netc. Evolution again points out a long gradation of forms of faith, if\nwe compare the lower, middle, and higher races.\n\nCivilized races are distinguished from barbaric by the formation of\nstates with an extensive division of labor. The social organism is\nnot only larger and more powerful, but is capable of a greater variety\nof achievements, the functions of the various states and classes of\nworkers being more highly differentiated and mutually complementary\n(like the cells and tissues in the higher animal body of the metazoa).\nNutrition is easier and more luxurious. Art and science are well\ndeveloped. A great advance is seen in regard to religion, the numerous\ngods being generally conceived as manlike spirits, and finally\nsubordinated to a chief god. The belief in miracles flourishes greatly\nin poetry; in philosophy it is more and more restricted. In the end,\nthe working of miracles is limited monotheistically to one god, or to\nhis priests and other men to whom he communicates the power.\n\nModern civilization in the narrower sense, as a contrast to the\nolder civilization, opens, in my opinion, at the beginning of the\nsixteenth century. At that time took place some of the greatest\nachievements of human thought among civilized peoples, and these\nbroke the chains of tradition and gave a fresh impetus to progress.\nMen's own mental outlook was widened by the system of Copernicus\nand the Reformation freed them from the yoke of the papacy. Shortly\nbefore, the discovery of the New World and the circumnavigation of\nthe globe had convinced men of the rotundity of the earth; geography,\nnatural history, medicine, and other sciences gained inspiration and\nindependence; printing and engraving provided an important means of\nspreading the new knowledge. This fresh impetus was chiefly of service\nto philosophy, which now more and more rejected the dictation of the\nChurch and superstition; though it was far from casting off the fetters\naltogether. This was not generally possible until the nineteenth\ncentury, when empirical science assumed an enormous importance, and in\nthe ensuing period of speculation the physical conception of the world\ngained more and more on the metaphysical. Pure knowledge, thus grounded\non science, entered into sharper conflict than ever with religious\nfaith. If, as in the preceding cases, we distinguish three stages in\nthe development of modern civilization, we recognize the progressive\nliberation from superstition by scientific knowledge.\n\nWhen we compare the higher forms of religion of civilized nations we\nfind the same emotional cravings and thought-processes constantly\nrecurring, and the belief in miracles developing in much the same\nway. The three founders of the great monotheistic Mediterranean\nreligion--Moses, Christ, and Mohammed--were equally regarded as\nwonder-working prophets, having direct intercourse with God in virtue\nof their special gifts, and transmitting his commands to men in the\nshape of laws. The extraordinary authority they enjoy, which has\ngiven so much prestige to the religions they founded, is grounded for\nordinary people on their miraculous powers--the healing of the sick,\nthe raising of the dead, the expulsion of devils, and so on. If we\nexamine the miracles of Christ as they are given in the gospels, they\nrun counter to the laws of nature and rational explanation just in\nthe same way as the similar miracles of Buddha and Brahma in Hindoo\nmythology, or of Mohammed in the Koran. The same must be said of the\nbelief in the miracle of the bread and wine in the Lord's supper,\nand the like. The Creed which was probably drawn up by the leaders\nof the Christian communities of the second century, and received its\nfinal and present form in the Church of South Gaul in the fourth\nand fifth centuries, has been obligatory for Christians for fifteen\nhundred years, and recognized by both Church and State as compulsory.\nThis Apostles' Creed was also recognized in Luther's catechism to\nbe fundamental, and is taught in all Protestant and Roman Catholic\nschools (though not in the Greek Catholic) as the foundation of\nreligious instruction. This extraordinary prestige of the Apostles'\nCreed, and its great influence on the education of the young, no less\nthan its glaring inconsistency with rational knowledge, compel us to\ndevote a few pages to a critical examination of its three articles.\n\nThe first article of the Creed deals with creation, and runs: \"I\nbelieve in God, the Father Almighty, Creator of heaven and earth.\"\nThe modern science of evolution has shown that there never was any\nsuch creation, but that the universe is eternal and the law of\nsubstance all-ruling. God himself is anthropomorphically conceived as\nan \"Almighty Creator\" and the Father of man; heaven (in the sense of\nthe geocentric system) is imagined as a great blue vault spanning the\nearth. The notion of this \"personal God\" as an intelligent, immaterial\nbeing, creating the material world out of nothing, is wholly irrational\nand meaningless. That Luther accepted this childish and scientifically\nworthless idea is clear from his commentary on the first article--\"What\nis that?\"\n\nThe second article of the Creed deals with the dogma of salvation\nin the following words: \"I believe in Jesus Christ, his only son,\nour Lord, who was conceived of the Holy Ghost, born of the Virgin\nMary, suffered under Pontius Pilate, was crucified, dead, and buried,\ndescended into hell, on the third day rose again from the dead,\nascended into heaven, sitteth at the right hand of God, the Father\nAlmighty, whence he will come to judge the living and the dead.\" As\nthese dogmas of the second article contain the chief points of the\nredemption theory, and are still treasured by millions of educated\npeople, it is necessary to point out their flagrant opposition to pure\nreason. The chief evil of such creeds is that children, who are yet\nincapable of reflecting, are forced to learn them by heart. They then\nremain unchallenged as revealed truths.\n\nThe myth of the conception and birth of Jesus Christ is mere fiction,\nand is at the same stage of superstition as a hundred other myths of\nother religions. Of the three persons who are mysteriously blended\nin the triune God, the son Christ is supposed to be begotten by both\nFather and Holy Ghost, parthenogenetically through the Virgin Mary. I\nhave dealt with the physiology of parthenogenesis in the seventeenth\nchapter of the _Riddle_. The curious adventures of Christ after his\ndeath, the descent into hell, resurrection, and ascension, are also\nfantastic myths due to the narrow geocentric ideas of an uneducated\npeople. Troelslund has admirably explained the strong influence they\nhave had in his interesting book, _The Idea of Heaven and of the\nWorld_.[6] The idea of the \"last judgment,\" with Christ sitting on the\nright hand of the Father, as many famous medi\u00e6val pictures represent\n(notably Michael Angelo's in the Sistine Chapel at the Vatican), is\nanother outcome of a thoroughly childish and anthropomorphic attitude.\n\nIt is remarkable that this second article of the Creed says nothing\nabout \"redemption,\" which forms its heading [in Germany]. Luther has\ndealt with it in his commentary. Christ is believed to have suffered a\npainful death, like many thousand other martyrs, for his conviction of\nthe truth of his faith and teaching--which reminds one of the more than\na hundred thousand men who were done to death by the Inquisition and in\nthe religious wars of the Middle Ages; but not one of the millions of\nministers who preach on it every Sunday seems to have shown a rational\ncausal connection of this death with the alleged redemption from sin\nand death. The whole of this story of redemption has sprung from the\nprimitive, obscure, ethical ideas of uneducated races, especially the\ncrude belief in the propitiatory power of human sacrifice. It has\nno practical moral value except for those who believe in personal\nimmortality--a scientifically untenable dogma. Whoever builds on this\nempty promise of a better life beyond may soothe himself with this\nhope, and reconcile himself to the thousand ills and defects of this\nworld. But the man who studies this life as it really is will not\nfind that the belief in redemption has brought any real improvement.\nWant and misery and sin are as prevalent as ever; indeed, our modern\ncivilization has, in many respects, increased them.\n\nThe third and last article of the Apostles' Creed runs: \"I believe\nin the Holy Ghost, the holy Catholic Church, the communion of\nsaints, the forgiveness of sins, the resurrection of the body, and\nlife everlasting.\" In the curious commentary that Luther made on\nthis article in his catechism, he said that \"man cannot believe\nof his own reason in Jesus Christ\"--which is very true--but the\nHoly Ghost must lead him thereto with his grace; but how the third\nperson of the Trinity effects this enlightenment and sanctification\nhe did not explain. What is meant by the \"communion of saints\" and\nthe \"holy Catholic Church\" must be gathered in the light of their\nhistory--especially the history of Romanism. This most powerful and\nstill influential section of the Christian Church, which especially\nclaims the title of Catholic and \"the one ark of salvation,\" is really\na most pitiful caricature of pure primitive Christianity. It has, with\nconsummate skill, succeeded in preaching the beneficent teaching of\nChrist in theory and doing just the opposite in practice; we need only\nrecall the Inquisition, the dark history of the Middle Ages, and the\npolitical hierarchy which still dominates so much of civilization.\n\nHowever, by far the most important clause in the third article is\nthe final expression of belief in \"the resurrection of the body and\nlife everlasting.\" That this greatest \"wonder of life\" was originally\nconceived in a purely material form is evident from thousands of\npictures in which famous painters have realistically depicted the\nresurrection of the dead, the a\u00ebrial flight of the happy souls of the\nblessed, and the torments of the damned in hell. It is thus conceived\nstill by the majority of believers who take eternal life to be an\n\"enlarged and improved edition\" of life here below. This is equally\ntrue of Christian and Mohammedan pictures and of the athanatist ideas\nthat prevailed in other religions long before Christ was born, even\nof the first rudiments of the belief in primitive races. As long as\nthe geocentric theory prevailed, and the heavens were thought to be a\nsort of blue glass bell, illumined by thousands of little stars and\nthe lamp of the sun, arching like a vault over the flat earth, and\nthe fires of hell burned in the cellars below, this barbaric notion\nof a resurrection of the body and a last judgment could easily be\nmaintained. But its roots were destroyed when Copernicus refuted the\ngeocentric theory in 1545; and athanatism became quite untenable when\nDarwin shattered the dogma of anthropocentricism. Not only the crude\nolder materialistic idea of eternal life, but also the refined new\nspiritualistic version, has been rendered untenable by the progress of\nscience in the nineteenth century. I have shown this in the eleventh\nchapter of the _Riddle_, which closes with the words: \"If we take a\ncomprehensive glance at all that modern anthropology, psychology,\nand cosmology teach with regard to athanatism, we are forced to this\ndefinite conclusion. The belief in the immortality of the human soul\nis in hopeless contradiction with the most solid empirical truths of\nmodern science.\"[7]\n\nThe great influence which has been exercised on civilized nations\nby the Christian beliefs, supported by the practical exigencies of\nthe state, for thousands of years, was chiefly seen in the crude\nsuperstition of the mass of the people. Confessions of faith became\nas much a matter of routine as the latest fashion in dress or the\nlatest custom, etc. But even the majority of the philosophers were\nmore or less subordinated to the influence. It is true that a few\ngreat thinkers freed themselves by the use of pure reason at an early\ndate from the prevalent superstition, and framed systems apart from\ntradition and the priests. But most philosophers could not rise to\nthe altitude of these brave Free-thinkers; they remained \"school-men\"\nin the literal sense, dependent on the dictation of authority, the\ntraditions of the school, and the dogmas of the Church. Philosophy\nwas the \"handmaid\" of theology and ecclesiasticism. If we examine the\nhistory of philosophy in this light, we find in it a struggle for\ntwenty-five hundred years between two great tendencies--the dualism of\nthe majority (with theological and mystic leanings) and the monism of\nthe minority (with rationalistic and naturalistic disposition).\n\nEspecially notable are those great Free-thinkers of classic antiquity\nwho taught a monistic view of life in the sixth century before\nChrist--the Ionic natural philosophers, Thales, Anaximander, and\nAnaximenes; and a little later, Heraclitus, Empedocles, and Democritus.\nThey made the first thorough attempt to explain the world on rational\nprinciples, independently of all mythological tradition and theological\ndogmas. However, these remarkable efforts to found a primitive monism,\nwhich found so finished an expression in the _De rerum natura_ of the\ngreat poet-philosopher, Lucretius Carus (98-54 B.C.), were shortly\nthrust out by the spread--through Plato's curious dualism--of the\nbelief in the immortality of the soul and the transcendental world of\nideas.\n\nThe Eleatics, Parmenides and Zeno, had foreshadowed in the fifth\ncentury the division of philosophy into two branches; but Plato and\nhis pupil Aristotle (in the fourth century B.C.) succeeded in gaining\ngeneral acceptance for this dualism and antithesis of physics and\nmetaphysics. Physics devoted itself on the ground of experience to\nthe study of the phenomena of things, leaving their real essences (or\nnoumena) that lay behind the phenomena to metaphysics. These inner\nessences are transcendental and inaccessible to empirical research;\nthey form the metaphysical world of eternal ideas, which is independent\nof the real world, and has its highest unity in God, as the Absolute.\nThe soul, an eternal idea that dwells for a time in the passing human\nbody, is immortal. This consistent dualism of Plato's system, with\nits sharp antithesis of this world and the next, of body and soul, of\nworld and God, is its chief characteristic. It became all the more\ninfluential when Plato's pupil Aristotle blended it with his empirical\nmetaphysics, based on ample scientific experience, and pointed out the\nidea in the entelechy, or purposively acting principle, of every being;\nand especially when Christianity (three hundred years afterwards) found\nin this dualism a welcome philosophic support of its own transcendental\ntendency.\n\nIn the course of the thousand years which historians call the Middle\nAges, and which are usually dated from the fall of the Roman Empire\n(476) to the discovery of America (1492), the superstition of civilized\nraces reached its highest development. The authority of Aristotle was\nparamount in philosophy; it was used by the dominant Church for its\nown purposes. But the influence of the Christian faith, with all the\ngay coloring which the fairy-tales of the Bible added to its structure\nof dogmas, was seen much more in practical life. In the foreground of\nbelief were the three central dogmas of metaphysics, to which Plato had\nfirst given complete expression--the personal God as creator of the\nworld, the immortality of the soul, and the freedom of the human will.\nAs Christianity laid the greatest theoretical stress on the first two\ndogmas and the greatest practical stress on the third, metaphysical\ndualism soon prevailed on all sides. Especially inimical to scientific\ninquiry was the Christian contempt of nature and its belittlement\nof earthly life in view of the eternal life to come. As long as the\nlight of philosophical criticism in any form was extinguished, the\nflower-garden of religious poetry flourished exceedingly and the idea\nof miracle was taken as self-evident. We know what the practical result\nof this superstition was from the ghastly history of the Middle Ages,\nwith its Inquisition, religious wars, instruments of torture, and\ndrowning of witches. In the face of the current enthusiasm for the\nromantic side of medi\u00e6valism, the Crusades and Church art, we cannot\nlay too much stress on these dark and bloody pages of its chronicles.\n\nAn impartial study of the immense progress made by science in the\ncourse of the nineteenth century shows convincingly that the three\ncentral metaphysical dogmas established by Plato have become untenable\nfor pure reason. Our clear modern insight into the regularity and\ncausative character of natural processes, and especially our knowledge\nof the universal reign of the law of substance, are inconsistent with\nbelief in a personal God, the immortality of the soul, and the freedom\nof the will. If we find this threefold superstition still widely\nprevalent, and even retained by academic philosophers as an unshakable\nconsequence of \"critical philosophy,\" we must trace this remarkable\nfact chiefly to the great prestige of Immanuel Kant. His so-called\ncritical system--really a hybrid product of the crossing of pure reason\nwith practical superstition--has enjoyed a greater popularity than any\nother philosophy, and we must stop to consider it for a moment.\n\nI have described in chapters xiv. and xx. of the _Riddle_ the profound\nopposition between my monistic system and Kant's dualistic philosophy.\nIn the appendix to the popular edition, especially, I have pointed out\nthe glaring contradictions of his system, which other philosophers\nhave often detected and criticised. Whenever there is question of his\nteaching one must ask: \"Which Kant do you mean? Kant I., the founder of\nthe monistic cosmogony, the critical formulator of pure reason; or Kant\nII., the author of the dualistic criticism of judgment, the dogmatic\ndiscoverer of practical reason?\" These contradictions are partly due\nto the psychological metamorphoses which Kant underwent (_Riddle_,\nchapter vi.), partly to the perennial conflict between his scientific\nbias towards a mechanical explanation of this world and his religious\ncraving (an outcome of heredity and education) and mystic belief in a\nlife beyond. This culminates in the distinction between the world of\nsense and the world of spirit. The sense world (_mundus sensibilis_)\nlies open to our senses and our intellect, and is empirically knowable\nwithin certain limits. But behind it there is the spiritual world\n(_mundus intelligibilis_) of which we know, and can know, nothing;\nits existence (as the thing in itself) is, however, assured by our\nemotional needs. In this transcendental world dwells the power of\nmysticism.\n\nIt is said to be the chief merit of Kant's system that he first\nclearly stated the problem: \"How is knowledge possible?\" In trying to\nsolve this problem introspectively, by a subtle analysis of his own\nmental activity, he reached the conviction that the most important\nand soundest of all knowledge--namely, mathematical--consists of\nsynthetic _a priori_ judgments, and that pure science is only possible\non condition that there are strict _a priori_ ideas, independent of\nall experience, without _a posteriori_ judgments. Kant regarded this\nhighest faculty of the human mind as innate, and made no inquiry into\nits development, its physiological mechanism, and its anatomic organ,\nthe brain. Seeing the very imperfect knowledge which human anatomy\nhad of the complicated structure of the brain at the beginning of the\nnineteenth century, it was impossible to have at that time a correct\nidea of its physiological function.\n\nWhat seems to us to-day to be an innate capacity, or an _a priori_\nquality, of our phronema, is really a phylogenetic result of a long\nseries of brain-adaptations, formed by _a posteriori_ sense-perceptions\nand experiences.\n\nKant's much-lauded critical theory of knowledge is therefore just as\ndogmatic as his idea of \"the thing in itself,\" the unintelligible\nentity that lurks behind the phenomena. This dogma is erroneously built\non the correct idea that our knowledge, obtained through the senses, is\nimperfect; it extends only so far as the specific energy of the senses\nand the structure of the phronema admit. But it by no means follows\nthat it is a mere illusion, and least of all that the external world\nexists only in our ideas. All sound men believe, when they use their\nsenses of touch and space, that the stone they feel fills a certain\npart of space, and this space does really exist. When all men who can\nsee agree that the sun rises and sets every day, this proves a relative\nmotion of the two heavenly bodies, and so the real existence of time.\nSpace and time are not merely necessary forms of intuition for human\nknowledge, but real features of things, existing quite independently of\nperception.\n\nThe increasing recognition of fixed natural laws which accompanied the\ngrowth of science in the nineteenth century was bound to restrict more\nand more the blind faith in miracles. There are three chief reasons\nwhy we find this, nevertheless, still so prevalent--the continued\ninfluence of dualistic metaphysics, the authority of the Christian\nChurch, and the pressure of the modern state in allying itself with\nthe Church. These three strong bulwarks of superstition are so hostile\nto pure reason and the truth it seeks that we must devote special\nattention to them. It is a question of the highest interests of\nhumanity. The struggle against superstition and ignorance is a fight\nfor civilization. Our modern civilization will only emerge from it in\ntriumph, and we shall only eliminate the last barbaric features from\nour social and political life, when the light of true knowledge has\ndriven out the belief in miracles and the prejudices of dualism.\n\nThe remarkable history of philosophy in the nineteenth century, which\nhas not yet been written with complete impartiality and knowledge,\nshows us in the first place an ever-increasing struggle between the\nrising young sciences and the paramount authority of tradition and\ndogma. In the first half of the century the various branches of biology\nmade progress without coming into direct collision with natural\nphilosophy. The great advance of comparative anatomy, physiology,\nembryology, paleontology, the cell-theory, and classification,\nprovided scientists with such ample material that they attached\nlittle importance to speculative metaphysics. It was otherwise in the\nsecond half of the nineteenth century. Soon after its commencement\nthe controversy about the immortality of the soul broke out, in\nwhich Moleschott (1852), B\u00fcchner, and Carl Vogt (1854) contended for\nthe physiological dependence of the soul on the brain, while Rudolph\nWagner endeavored to maintain the prevailing metaphysical idea of its\nsupernatural character. Then Darwin especially initiated in 1859 that\nvast reform in biology which brought to light the natural origin of\nspecies and shattered the miracle of creation. When the application\nof the theory of descent and the biogenetic law to man was made by\nanthropogeny (1874), and his evolution from a series of other mammals\nwas proved, the belief in the immortality of the soul, the freedom\nof the will, and an anthropomorphic deity lost its last support.\nNevertheless, these three fundamental dogmas continued to find favor\nin academic philosophy, which mostly followed the paths opened out by\nKant. Most of the representatives of philosophy at the universities\nare narrow metaphysicians and idealists, who think more of the fiction\nof the \"intelligible world\" than of the truth of the world of sense.\nThey ignore the vast progress made by modern biology, especially in\nthe science of evolution; and they endeavor to meet the difficulties\nwhich it creates for their transcendental idealism by a sort of verbal\ngymnastic and sophistry. Behind all these metaphysical struggles there\nis still the personal element--the desire to save one's immortality\nfrom the wreck. In this it comes into line with the prevailing\ntheology, which again builds on Kant. The pitiful condition of modern\npsychology is a characteristic result of this state of things. While\nthe empirical physiology and pathology of the brain have made the\ngreatest discoveries, the comparative anatomy and histology of the\nbrain have thrown light on the details of its elaborate structure, and\nthe ontogeny and phylogeny of the brain have proved its natural origin,\nthe speculative philosophy of the schools stands aside from it all,\nand in its introspective analysis of the functions of the brain will\nnot hear a word about the brain itself. It would explain the working\nof a most complicated machine without paying any attention to its\nstructure. It is, therefore, not surprising to find that the dualistic\ntheories established by Kant flourish at our universities as they did\nin the Middle Ages.\n\nIf the official philosophers, whose formal duty it is to study truth\nand natural law, still cling to the belief in miracles in spite of\nall the advance of empirical science, we shall not be surprised to\nfind this in the case of official theology. Nevertheless, the sense of\ntruth has prompted many unprejudiced and honorable theologians to look\ncritically at the venerable structure of dogma, and open their minds\nto the streaming light of modern science. In the first third of the\nnineteenth century a rationalistic section of the Protestant Church\nattempted to rid itself of the fetters of dogma and reconcile its\nideas with pure reason. Its chief leader, Schleiermacher, of Berlin,\nthough an admirer of Plato and his dualist metaphysics, approached\nvery close to modern pantheism. Subsequent rationalistic theologians,\nespecially those of the T\u00fcbingen school (Baur, Zeller, etc.), devoted\nthemselves to the historical study of the gospels and their sources and\ndevelopment, and thus more and more destroyed the base of Christian\nsuperstition. Finally, the radical criticism of David Friedrich\nStrauss showed, in his _Life of Jesus_ (1835), the mythological\ncharacter of the whole Christian system. In his famous work, _The Old\nand New Faith_ (1872), this honorable and gifted theologian finally\nabandoned the belief in miracles, and turned to natural knowledge and\nthe monistic philosophy for the construction of a rational view of\nlife on the basis of critical experience. This work has lately been\ncontinued by Albert Kalthoff. Moreover, many modern theologians (such\nas Savage, Nippold, Pfleiderer, and other liberal Protestants) have\nendeavored in various ways to obtain a certain recognition for the\nclaims of progressive science, and reconcile them with theology, while\ndiscarding the belief in the miraculous. However, these rationalistic\nefforts, based on monistic or pantheistic views, are still isolated and\napparently without effect. The great majority of modern theologians\nadhere to the traditional teaching of the Church, whose columns and\nwindows are still everywhere adorned with miracles. While a few liberal\nProtestants restrict their faith to the three fundamental dogmas, most\nof them still believe in the myths and legends which fill the pages of\nthe gospels. This orthodoxy is, moreover, encouraged of late by the\nconservative and reactionary attitude taken up by many governments on\npolitical grounds.\n\nMost modern governments maintain the connection with the Church in the\nidea that the traditional belief in the miraculous is the best security\nfor their own continuance. Throne and altar must protect and support\neach other. However, this conservative-Christian policy meets two\nobstacles in an increasing measure. On the one hand, the ecclesiastical\nhierarchy is always trying to set its spiritual power above the secular\nand make the state serve its own purposes; and, on the other hand, the\nmodern right of popular representation affords an opportunity to make\nthe voice of reason heard and oppose the reactionary conservatives\nwith opportune reforms. The chief rulers and the ministers of public\ninstruction, who have a great influence in this struggle, generally\nfavor the teaching of the Church, not out of conviction of its truth,\nbut because they think knowledge brings unrest, and because docile and\nignorant subjects are easier to rule than educated and independent\ncitizens. Hence it is that we now hear so much on every occasion, in\nspeeches from the throne and at banquets, at the opening of churches\nand the unveiling of monuments, from able and influential speakers, of\nthe value of faith. They would give the palm to faith in its struggle\nwith knowledge. Thus we get this paradoxical situation in educated\ncountries (such as Prussia), that encouragement is given at once to\nmodern science and technical training and to the orthodox Church,\nwhich is its deadly enemy. As a rule, it is not stated in these florid\norations to how many and what kind of miracles this precious faith must\nextend. Nevertheless, we may yet, in view of the spread of intellectual\nreaction in Germany, see it made obligatory for at least all priests,\nteachers, and other servants of the state to profess a belief in the\nthree fundamental mysteries--the triune God of the catechism, the\npersonal immortality of the soul, and the absolute freedom of the human\nwill--and even in many of the other miracles which are found in the\ngospels, sacred legends, and religious journals of our time.\n\nThe refined belief in the miraculous embodied in Kant's practical\nphilosophy assumed many different forms among his followers, the\nNeo-Kantians, approaching sometimes more and sometimes less to the\nconventional beliefs. Through a long series of variations, which still\ncontinue to develop, it is gradually passing into the cruder form of\nsuperstition which we find popular to-day as spiritism, and which\nprovides the basis for what is called occultism. Kant himself, in\nspite of his subtle and clear critical faculty, had a decided leaning\nto mysticism and positive dogmatism, which showed itself especially\nin his later years. He thought a good deal of Swedenborg's idea of\nthe spirit world forming a universe apart, and compared this to his\n_mundus intelligibilis_. Among the natural philosophers of the first\nhalf of the nineteenth century, Schelling (in his later writings),\nSchubert (in his _History of the Soul_ and _Observations on the Dark\nSide of Science_), and Perty (in his mystic anthropology) especially\ninvestigated the mysterious phenomena of mental action, and sought\nto connect them with the physiological functions of the brain on the\none hand and supernatural spiritual agencies on the other. Modern\nspook-seeking has no more value than medi\u00e6val magic, cabalism,\nastrology, necromancy, dream-interpretation, and invocation of the\ndevil.\n\nWe must put at the same stage of superstition the spiritism and\noccultism we find mentioned so much in modern literature. There are\nalways thousands of credulous folk in educated countries who are\ntaken in by the performances of the spiritists and their media, and\nare ready to believe the unbelievable. Spirit-rapping, table-turning,\nspirit-writing, the materialization and photographing of deceased\nsouls, find credit, not only among the uneducated masses, but even\namong the most cultured, and sometimes among imaginative scientists.\nIt has been proved without avail by numbers of impartial observations\nand experiments that these occultist performances depend partly on\nconscious fraud and partly on careless self-deception. _Mundus vult\ndecipi_--\"the world wishes to be taken in\"--as the old saying has it.\nThis spiritistic fraud is particularly dangerous when it clothes itself\nwith the mantle of science, makes use of the physiological phenomena\nof hypnotism, and even assumes a monistic character. Thus, for\ninstance, one of the best-known occultist writers, Karl du Prel, has\nwritten, not only a _Philosophy of Mysticism and Studies of Scientific\nSubjects_, but also (1888) a _Monistic Psychology_, which is dualistic\nfrom beginning to end. In these popular writings lively imagination\nand brilliant presentation are combined with a most flagrant lack of\ncritical sense and of knowledge of the elements of biology (_cf._\nchapter xvi. of the _Riddle_). It seems that the hereditary bias\ntowards mysticism and superstition is not yet eliminated even from\nthe educated mind of our time. It is to be explained phylogenetically\nby inheritance from prehistoric barbarians and savages, in whom\nthe earliest religious ideas were wholly dominated by animism and\nfetichism.\n\n\n\n\nIV\n\nTHE SCIENCE OF LIFE\n\n Object of biology--Relation to the other sciences--General\n and special biology--Natural philosophy--Monism:\n hylozoism, materialism, dynamism--Naturalism--Nature and\n spirit--Physics--Metaphysics--Dualism--Freedom and natural law--God\n in biology--Realism--Idealism--Branches of biology--Morphology and\n physiology--Anatomy and biogeny--Ergology and perilogy.\n\n\nThe broad realm of science has been vastly extended in the course of\nthe nineteenth century. Many new branches have established themselves\nindependently; many new and most fruitful methods of research have\nbeen discovered, and have been applied with the greatest practical\nsuccess in furthering the advance of modern thought. But this enormous\nexpansion of the field of knowledge has its disadvantages. The\nextensive division of labor it has involved has led to the growth\nof a narrow specialism in many small sections; and in this way the\nnatural connection of the various provinces of knowledge, and their\nrelation to the comprehensive whole, have been partly or wholly lost\nsight of. The importation of new terms which are used in different\nsenses by one-sided workers in the various fields of science has caused\na good deal of misunderstanding and confusion. The vast structure\nof science tends more and more to become a tower of Babel, in the\nlabyrinthic passages of which few are at their ease and few any longer\nunderstand the language of other workers. In these circumstances, it\nseems advisable, at the commencement of our philosophic study of \"the\nwonders of life,\" to form a clear idea of our task. We must carefully\ndefine the place of biology among the sciences, and the relation of\nits various branches to each other and to the different systems of\nphilosophy.\n\nIn the broadest sense in which we can take it, biology is the whole\nstudy of organisms or living beings. Hence not only botany (the science\nof plants) and zoology (the science of animals), but also anthropology\n(the science of man), fall within its domain. We then contrast with it\nall the sciences which deal with inorganic or lifeless bodies, which\nwe may collectively call abiology (or anorganology); to this belong\nastronomy, geology, mineralogy, hydrology, etc. This division of the\ntwo great branches of science does not seem difficult in view of the\nfact that the idea of life is sharply defined physiologically by its\nmetabolism and chemically by its plasm; but when we come to study the\nquestion of abiogenesis (chapter xv.) we shall find that this division\nis not absolute, and that organic life has been evolved from inorganic\nnature. Moreover, biology and abiology are connected branches of\ncosmology, or the science of the world.\n\nWhile the idea of biology is now usually taken in this broad sense in\nmost scientific works and made to embrace the whole of living nature,\nwe often find (especially in Germany) a narrower application of the\nterm. Many authors (mostly physiologists) understand by it a section of\nphysiology--namely, the science of the relations of living organisms to\nthe external world, their habitat, customs, enemies, parasites, etc.\nI proposed long ago to call this special part of biology \u0153cology\n(the science of home-relations), or bionomy. Twenty years later others\nsuggested the name of ethology. To call this special study any longer\nbiology in the narrower sense is very undesirable, because it is the\nonly name we have for the totality of the organic sciences.\n\nLike every other science, biology has a general and a special part.\nGeneral biology contains general information about living nature;\nthis is the subject of the present study of the wonders of life. We\nmight also describe it as biological philosophy, since the aim of true\nphilosophy must be the comprehensive survey and rational interpretation\nof all the general results of scientific research. The innumerable\ndiscoveries of detailed facts which observation and experiment give\nus, and which are combined into a general view of life in philosophy,\nform the subject of empirical science. As the latter, on the side of\nthe organic world, or as empirical biology, forms the first object of\nthe science of life, and seeks to effect in the system of nature a\nlogical arrangement and summary grouping of the countless special forms\nof life, this special biology is often wrongly called the science of\nclassification.\n\nThe first comprehensive attempt to reduce to order and unity the\nample biological material which systematic research had accumulated\nin the eighteenth century was made by what we call \"the older natural\nphilosophy\" at the beginning of the nineteenth century. Reinhold\nTreviranus (of Bremen) had made a suggestive effort to accomplish this\ndifficult task on monistic principles in his _Biology, or Philosophy of\nLiving Nature_ (1802). Special importance attaches to the year 1809, in\nwhich Jean Lamarck (of Paris) published his _Philosophie Zoologique_,\nand Lorentz Oken (of Jena) his _Manual of Natural Philosophy_. I have\nfully appreciated the service of Lamarck, the founder of the theory\nof descent, in my earlier writings. I have also recognized the great\nmerit of Lorentz Oken, who not only aroused a very wide interest in\nthis science by his _General Natural History_, but also put forward\nsome general observations of great value. His \"infamous\" theory of a\nprimitive slime, and the development of infusoria out of it, is merely\nthe fundamental idea of the theory of protoplasm and the cell which\nwas long afterwards fully recognized. These and other services of the\nolder natural philosophy were partly ignored and partly overlooked,\nbecause they went far beyond the scientific horizon of the time, and\ntheir authors to an extent lost themselves in airy and fantastic\nspeculations. The more scientists confined themselves in the following\nhalf-century to empirical work and the observation and description of\nseparate facts, the more it became the fashion to look down on all\n\"natural philosophy.\" The most paradoxical feature of the situation was\nthat purely speculative philosophy and idealist metaphysics had a great\nrun at the same time, and their castles in the air, utterly destitute\nof biological foundation, were much admired.\n\nThe magnificent reform of biology which Darwin initiated in 1859 by\nhis epoch-making _Origin of Species_ gave a fresh impulse to natural\nphilosophy. As this work not only used the rich collection of facts\nalready made in proof of the theory of descent, but gave it a new\nfoundation in the theory of selection (Darwinism properly so called),\neverything seemed to call for the embodiment of the new conception of\nnature in a monistic system. I made the first effort to do this in my\n_General Morphology_ (1866). As this found few supporters among my\ncolleagues, I undertook in my _History of Creation_ (1868) to make\nthe chief points of the system accessible to the general reader. The\nremarkable success of this book (a tenth edition of it appearing in\n1902) emboldened me at the end of the nineteenth century to state the\ngeneral principles of my monistic philosophy in my _Riddle of the\nUniverse_. About the same time (1899) there appeared the work of the\nKiel botanist, Johannes Reinke, _The World as Reality_; and two years\nafterwards he followed it up with a supplementary volume, _Introduction\nto Theoretic Biology_. As Reinke treats the general problems of natural\nphilosophy from a purely mystic and dualistic point of view, his ideas\nare diametrically opposed to my monistic and naturalistic principles.\n\nThe history of philosophy describes for us the infinite variety of\nideas that men have formulated during the last three thousand years\non the nature of the world and its phenomena. \u00dcberweg has given us,\nin his excellent _History of Philosophy_, a thorough and impartial\naccount of these various systems. Fritz Schultze has published a\nclear and compendious \"tabulated outline\" of them in thirty tables in\nhis genealogical tree of philosophy, and at the same time shown the\nphylogeny of ideas. When we survey this enormous mass of philosophic\nsystems from the point of view of general biology, we find that we can\ndivide them into two main groups. The first and smaller group contains\nthe monistic philosophy, which traces all the phenomena of existence\nto one single common principle. The second and larger group, to which\nmost philosophic systems belong, constitutes the dualistic philosophy,\naccording to which there are two totally distinct principles in the\nuniverse. These are sometimes expressed as God and the world, sometimes\nas the spiritual world and material world, sometimes as mind and\nmatter, and so on. In my opinion, this antithesis of monism and dualism\nis the most important in the whole history of philosophy. All other\nsystems are only variations of one or the other of these, or a more or\nless obscure combination of the two.\n\nThe form of monism which I take to be the most complete expression\nof the general truth, and which I have advocated in my writings for\nthirty-eight years, is now generally called hylozoism. This expresses\nthe fact that all substance has two fundamental attributes; as matter\n(_hyle_) it occupies space, and as force or energy it is endowed with\nsensation (_cf._ chapter xix.). Spinoza, who gave the most perfect\nexpression to this idea in his \"philosophy of identity,\" and most\nclearly treated the notion of substance (as the all-embracing essence\nof the world), clothes it with two general attributes--extension\nand thought. Extension is identical with real space, and thought\nwith (unconscious) sensation. The latter must not be confused with\nconscious human thought; intelligence is not found in substance, but is\na special property of the higher animals and man. Spinoza identifies\nhis substance with nature and God, and his system is accordingly\ncalled pantheism; but it must be understood that he rejects the\nanthropomorphic, personal idea of deity.\n\nA good deal of the infinite confusion that characterizes the conflicts\nof philosophers over their systems is due to the obscurity and\nambiguity of many of their fundamental ideas. The words \"substance\"\nand \"God,\" \"soul\" and \"spirit,\" \"sensation\" and \"matter,\" are used\nin the most different and changing senses. This is especially true\nof the word \"materialism,\" which is often wrongly taken to be\nsynonymous with monism. The moral bias of idealism against _practical_\nmaterialism (or pure selfishness and sensualism) is forthwith\ntransferred to theoretical materialism, which has nothing to do with\nit; and the strictures which are justly urged against the one are\nmost unjustifiably applied to the other. Hence it is important to\ndistinguish very carefully between these two meanings of materialism.\n\nTheoretical materialism (or hylonism), as a realistic and monistic\nphilosophy, is right in so far as it conceives matter and force to be\ninseparably connected, and denies the existence of immaterial forces.\nBut it is wrong when it denies all sensation to matter, and regards\nactual energy as a function of dead matter. Thus, in ancient times\nDemocritus and Lucretius traced all phenomena to the movements of dead\natoms, as did also Holbach and Lamettrie in the eighteenth century.\nThis view is held to-day by most chemists and physicists. They regard\ngravitation and chemical affinity as a mere mechanical movement of\natoms, and this, in turn, as the general source of all phenomena; but\nthey will not allow that these movements necessarily presuppose a\nkind of (unconscious) sensation. In conversation with distinguished\nphysicists and chemists I have often found that they will not hear a\nword about a \"soul\" in the atom. In my opinion, however, this must\nnecessarily be assumed to explain the simplest physical and chemical\nprocesses. Naturally I am not thinking of anything like the elaborate\npsychic action of man and the higher animals, which is often bound\nup with consciousness; we must rather descend the long scale of the\ndevelopment of consciousness until we reach the simplest protists,\nthe monera (chapter ix.). The psychic activity of these homogeneous\nparticles of plasm (for instance, the chromacea) rises very little\nabove that of crystals; as in the chemical synthesis in the moneron, so\nin crystallization we are bound to assume that there is a low degree\nof sensation (not of consciousness), in order to explain the orderly\narrangement of the moving molecules in a definite structure.\n\nThe prejudice against theoretical materialism (or materialistic monism)\nwhich still prevails so much is partly due to its rejection of the\nthree central dogmas of dualist metaphysics, and partly to a confusion\nof it with hedonism. This practical materialism in its extreme forms\n(as Aristippus of Cyrene and the Cyrenaic school, and afterwards\nEpicurus, taught it) finds the chief end of life in pleasure--at one\ntime crude, sensual pleasure, and at others spiritual pleasure. Up to a\ncertain point, this thirst for happiness and a pleasant and enjoyable\nlife is innate in every man and higher animal, and so far just; it only\nbegan to be censured as sinful when Christianity directed the thoughts\nof men to eternal life, and taught them that their life on earth was\nonly a preparation for the future. We shall see afterwards, when we\ncome to weigh the value of life (chapter xvii.), that this asceticism\nis unjustifiable and unnatural. But as every legitimate enjoyment can\nbecome wrong by excess, and every virtue be turned into vice, so a\nnarrow hedonism is to be condemned, especially when it allies itself\nwith egoism. However, we must point out that this excessive thirst for\npleasure is in no way connected with materialism, but is often found\namong idealists. Many convinced supporters of theoretical materialism\n(many scientists and physicians, for instance) lead very simple,\nblameless lives, and are little disposed to material pleasures. On the\nother hand, many priests, theologians, and idealist philosophers, who\npreach theoretical idealism, are pronounced hedonists in practice.\nIn olden times many temples served at one and the same time for the\ntheoretic worship of the gods and for practical excesses in the way\nof wine and love; and even in our day the luxurious and often vicious\nlives of the higher clergy (at Rome, for instance) do not fall far\nshort of the ancient models. This paradoxical situation is due to the\nspecial attractiveness of everything that is forbidden. But it is\nutterly unjust to extend the natural feeling against excessive and\negoistic hedonism to theoretical materialism and to monism. Equally\nunjust is the habit, still widely spread, of depreciating matter, as\nsuch, in favor of spirit. Impartial biology has taught us of late years\nthat what we call \"spirit\" is--as Goethe said long ago--inseparably\nbound up with matter. Experience has never yet discovered any spirit\napart from matter.\n\nOn the other hand, pure dynamism, now often called energism (and\noften spiritualism), is just as one-sided as pure materialism. Just\nas the latter takes one attribute of substance, matter, as the one\nchief cause of phenomena, dynamism takes its second attribute, force\n(_dynamis_). Leibnitz most consistently developed this system among\nthe older German philosophers; and Fechner and Z\u00f6llner have recently\nadopted it in part. The latest development of it is found in Wilhelm\nOstwald's _Natural Philosophy_ (1902). This work is purely monistic,\nand very ingeniously endeavors to show that the same forces are at\nwork in the whole of nature, organic and inorganic, and that these may\nall be comprised under the general head of energy. It is especially\nsatisfactory that Ostwald has traced the highest functions of the\nhuman mind (consciousness, thought, feeling, and will), as well as the\nsimplest physical and chemical processes (heat, electricity, chemical\naffinity, etc.), to special forms of energy, or natural force. However,\nhe is wrong when he supposes that his energism is an entirely new\nsystem. The chief points of it are found in Leibnitz; and other Leipzig\nscientists, especially Fechner and Z\u00f6llner, had come very close to\nsimilar spiritualistic views--the latter going into outright spiritism.\nOstwald's chief mistake is to take the terms \"energy\" and \"substance\"\nto be synonymous. Certainly his universal, all-creating energy is, in\nthe main, the same as the substance of Spinoza, which we have also\nadopted in our \"law of substance.\" But Ostwald would deprive substance\nof the attribute of matter altogether, and boasts of his _Refutation of\nMaterialism_ (1895). He would leave it only the one attribute, energy,\nand reduce all matter to immaterial points of force. Nevertheless,\nas chemist and physicist, he never gets rid of space-filling\nsubstance--which is all we mean by \"matter\"--and has to treat it and\nits parts, the physical molecules and chemical atoms (even if only\nconceived as symbols), daily as \"vehicles of energy.\" Ostwald would\nreject even these in his pursuit of the illusion of a \"science without\nhypotheses.\" As a fact, he is forced every day, like every other exact\nscientist, to assume and apply in practice the indispensable idea of\nmatter, and its separate particles, the molecules and atoms. Knowledge\nis impossible without hypotheses.\n\nMonism is best expressed as hylozoism, in so far as this removes\nthe antithesis of materialism and spiritualism (or mechanicism and\ndynamism), and unites them in a natural and harmonious system. Our\nmonistic system has been charged with leading to pure naturalism;\none of its most vehement critics, Frederick Paulsen, attaches so\nmuch importance to this stricture that he thinks it as dangerous\nas dogmatic clericalism. We may, therefore, usefully consider the\nidea of naturalism, and point out in what sense we accept it and\nidentify it with monism. The key to the position is in our monistic\nanthropogeny, our unprejudiced conviction, supported by every branch\nof anthropological research, of \"man's place in nature,\" as we have\nestablished it in the first section of the _Riddle_ (chapters ii.-v.).\nMan is a purely natural being, a placental mammal of the order of\nprimates. He was phylogenetically evolved in the course of the\nTertiary Period from a series of the lower primates (directly from\nthe anthropoid apes, but earlier from the cynocephali and lemures).\nSavage man, as we have him to-day in the Veddah or Australian negro, is\nphysiologically nearer to the apes than to highly civilized men.\n\nAnthropology (in the widest sense) is only a particular branch of\nzoology, to which we must assign a special position on account of its\nextreme importance. Hence all the sciences which relate to man and his\npsychic activity--especially what are called the moral sciences--must\nbe regarded from our monistic point of view as special branches of\nzoology and as natural sciences. Human psychology is inseparably\nconnected with comparative animal psychology, and this again with\nthat of the plants and protists. Philology studies in human speech a\ncomplicated natural phenomenon, which depends on the combined action\nof the brain-cells of the phronema, the muscles of the tongue, and\nthe vocal cords of the larynx, as much as the cry of mammals and the\nsong of birds do. The history of mankind (which we, in our curious\nanthropocentric mood, call the history of the world), and its highest\nbranch, the history of civilization, is connected by modern prehistoric\nscience directly with the stem-history of the primates and the other\nmammals, and indirectly with the phylogeny of the lower vertebrates.\nHence, when we consider the subject without prejudice, we do not find\na single branch of human science that passes the limits of natural\nscience (in the broadest sense), any more than we find nature herself\nto be supernatural.\n\nJust as monism, or naturalism, embraces the totality of science, so on\nour principles the idea of nature comprises the whole scientifically\nknowable world. In the strict monistic sense of Spinoza the ideas\nof God and Nature are synonymous for us. Whether there is a realm\nof the supernatural and spiritual beyond nature we do not know. All\nthat is said of it in religious myths and legends, or metaphysical\nspeculations and dogmas, is mere poetry and an outcome of imagination.\nThe imagination of civilized man is ever seeking to produce unified\nimages in art and science, and when it meets with gaps in these in the\nassociation of ideas it endeavors to fill them with its own creations.\nThese creations of the phronema with which we fill the gaps in our\nknowledge are called _hypotheses_ when they are in harmony with the\nempirically established facts, and _myths_ when they contradict the\nfacts: this is the case with religious myths, miracles, etc. Even\nwhen people contrast mind with nature, this is only a result, as a\nrule, of similar superstitions (animism, spiritism, etc.). But when we\nspeak of man's mind as a higher psychic function, we mean a special\nphysiological function of the brain, or that particular part of the\ncortex of the brain which we call the phronema, or organ of thought.\nThis higher psychic function is a natural phenomenon, subject, like\nall other natural phenomena, to the law of substance. The old Latin\nword _natura_ (from _nasci_, to be born) stands, like the corresponding\nGreek term _physis_ (from _phyo_--to grow), for the essence of the\nworld as an eternal \"being and becoming\"--a profound thought! Hence\nphysics, the science of the _physis_, is, in the broadest sense of the\nword, \"natural science.\"\n\nThe extensive division of labor which has taken place in science, on\naccount of the enormous growth of our knowledge in the nineteenth\ncentury and the rise of many new disciplines, has very much altered\ntheir relations to each other and to the whole, and has even given a\nfresh meaning and connotation to the term. Hence by physics, as it is\nnow taught at the universities, is usually understood only that part of\ninorganic science which deals with the molecular relations of substance\nand the mechanism of mass and ether, without regard to the qualitative\ndifferences of the elements, which are expressed in the atomic weight\nof their smallest particles, the atoms. The study of the atoms and\ntheir affinities and combinations belongs to chemistry. As this\nprovince is very extensive and has its special methods of research,\nit is usually put side by side with physics as of equal importance;\nin reality, however, it is only a branch of physics--chemistry is\nthe physics of the atoms. Hence, when we speak of a physico-chemical\ninquiry or phenomenon, we might justly describe it briefly as\n_physical_ (in the wider sense). Physiology, again, a particularly\nimportant branch of it, is in this sense the physics of living things,\nor the physico-chemical study of the living body.\n\nSince Aristotle dealt with the eternal phenomena of nature in the first\npart of his works, and called this _physics_, and with their inner\nnature in the second part, to which he gave the name of _metaphysics_,\nthe two terms have undergone many and considerable modifications. If\nwe restrict the term \"physics\" to the empirical study of phenomena (by\nobservation and experiment), we may give the name of metaphysics to\nevery hypothesis and theory that is introduced to fill up the gaps in\nit. In this sense the indispensable theories of physics (such as the\nassumption that matter is made up of molecules and atoms and electrons)\nmay be described as metaphysical; such also is our assumption that all\nsubstance is endowed with sensation as well as extension (matter).\nThis monistic metaphysics, which recognizes the absolute dominion of\nthe law of substance in all phenomena, but confines itself to the\nstudy of nature and abandons inquiry into the supernatural, is, with\nall its theories and hypotheses, an indispensable part of any rational\nphilosophy of life. To claim, as Ostwald does, that science must be\nfree from hypotheses is to deprive it of its foundations. But it is\nvery different with the current dualistic metaphysics, which holds that\nthere are two distinct worlds, and which we find in a hundred forms as\nphilosophic dualism.\n\nIf we understand by metaphysics the science of the ultimate ground of\nthings, springing from the rational demand for causes, it can only\nbe regarded, from the physiological point of view, as a higher and\nlate-developed function of the phronema. It could only arise with the\ncomplete development of the brain in civilized man. It is completely\nlacking among savages, whose organ of thought rises very little\nabove that of the most intelligent animals. The laws of the psychic\nlife of the savage have been closely studied by modern ethnology. It\nteaches us that the higher reason is not found in savages, and that\ntheir power of abstract thought and of forming concepts is at a very\nlow level. Thus, for instance, the Veddahs, who live in the forests\nof Ceylon, have not the general idea of trees, though they know and\ngive names to individual trees. Many savages cannot count up to five;\nthey never reflect on the ground of their existence or think of the\npast or future. Hence it is a great error for Schopenhauer and other\nphilosophers to define man as a \"metaphysical animal,\" and to seek\na profound distinction between man and the animal in the need for\na metaphysic. This craving has only been awakened and developed by\nthe progress of civilization. But even in civilized communities it\n(like consciousness) is not found in early youth, and only gradually\nemerges. The child has to learn to speak and think. In harmony with\nour biogenetic law, the child reproduces in the various stages of its\nmental development the whole of the gradations which lead from the\nsavage to the barbarian, and from the barbarian to the half-civilized,\nand on to the fully educated man. If this historical development of\nthe higher human faculties had always been properly appreciated, and\npsychology had been faithful to the comparative and genetic methods,\nmany of the errors of the current metaphysical systems would have been\navoided. Kant would not then have produced his theory of _a priori_\nknowledge, but would have seen that all that now seems to be _a priori_\nin civilized man was originally acquired by _a posteriori_ experiences\nin the long evolution of civilization and science. Here we have the\nroot of the errors which are distinctive of dualism and the prevailing\nmetaphysical transcendentalism.\n\nLike all science, biology is _realistic_--that is to say, it regards\nits object, the organisms, as really existing things, the features of\nwhich are to an extent knowable through our senses (_sensorium_) and\norgan of thought (_phronema_). At the same time, we know that these\ncognitive organs, and the knowledge they bring us, are imperfect, and\nthat there may be other features of organisms that lie beyond our means\nof perception altogether. But it by no means follows from this that,\nas our idealist opponents say, the organisms (and all other things)\nexist only in our mind (in the images in our cortex). Our pure monism\n(or hylozoism) agrees with realism in recognizing the unity of being\nof each organism, and denying that there is any essential distinction\nbetween its knowable phenomenon and its internal hidden essence (or\nnoumenon), whether the latter be called, with Plato, the eternal\n\"idea,\" or, with Kant, the \"thing in itself.\" Realism is not identical\nwith materialism, and may even be definitely connected with the very\nopposite, dynamism or energism.\n\nAs realism generally coincides with monism, so idealism is usually\nidentical with dualism. The two most influential representatives of\ndualism, Plato and Kant, said that there were two totally distinct\nworlds. Nature, or the empirical world, is alone accessible to our\nexperience, while the spiritual or transcendental world is not. The\nexistence of the latter is known to us only by the emotions or by\npractical reason; but we can have no idea of its nature. The chief\nerror of this theoretical idealism is the assumption that the soul is\na peculiar, immaterial being, immortal and endowed with _a priori_\nknowledge. The physiology and ontogeny of the brain (together with the\ncomparative anatomy and histology of the phronema) prove that the soul\nof man is, like that of all other vertebrates, a function of the brain,\nand inseparably bound up with this organ. Hence this idealist theory\nof knowledge is just as inconsistent with realistic biology as is the\npsycho-physical parallelism of Wundt or the psychomonism of more\nrecent physiologists, which in the end issues in a complete dualism of\nbody and mind. It is otherwise with _practical_ idealism. When this\npresents the symbols or ideals of a personal God, an immortal soul, and\nthe free-will as ethical stimuli, and uses them for their pedagogical\nworth in the education of the young, it may have a good influence for a\ntime, which is independent of their theoretical untenability.\n\nThe many branches of biology which have been developed independently\nin the course of the nineteenth century ought to remain in touch\nwith one another, and co-operate with a clear apprehension of their\ntask, if they are to attain their high purpose of framing a unified\nscience embracing the whole field of organic life. Unfortunately, this\ncommon aim is often lost sight of in the specialization of study;\nthe philosophical task is neglected in favor of the empirical. The\nconfusion that has ensued makes it desirable to determine the mutual\npositions of the various biological disciplines. I went into this\nsomewhat fully in my academic speech on the development and aim of\nzoology in 1869. But as this essay is little known, I will briefly\nresume the chief points of it.\n\nIn correspondence with the long-established distinction between the\nplant and the animal, the two chief branches of biology, zoology\nand botany, have developed side by side, and are represented by\ntwo different chairs in the universities. Independently of these,\nthere arose at the very beginning of scientific activity that field\nof inquiry which deals with human life in all its aspects--the\nanthropological disciplines and the so-called \"mental sciences\"\n(history, philology, psychology, etc.). Since the theory of descent has\nproved man's origin from vertebrate ancestors, and thus anthropology\nhas been recognized as a part of zoology, we have begun to understand\nthe inner historic connection between these various branches of\nanthropology, and to combine them in a comprehensive science of man.\nThe immense extent and the great importance of this science have\njustified the creation of late years of special chairs of anthropology.\nIt seems desirable to do the same for the science of the protists, or\nunicellular organisms. The cell theory, or cytology, as an elementary\npart of anatomy, has to be dealt with in both botany and zoology;\nbut the lowest unicellular representatives of both kingdoms, the\nprimitive plants (protophyta) and the primitive animals (protozoa), are\nso intimately connected, and throw so great a light, as independent\nrudimentary organisms, on the tissue cells in the _histon_, or\nmulticellular organism, that we must regard as a sign of progress the\nrecent proposal of Schaudinn to found a special institute and journal\nfor the science of protists. One very important section of it is\nbacteriology.\n\nThe practical division of biology, according to the extent of the\norganic kingdom, leads us to mark out four chief provinces of research:\nprotistology (the science of the unicellulars), botany (the science\nof plants), zoology (the science of animals), and anthropology (the\nscience of man). In each of these four fields we may then distinguish\nmorphology (the science of forms) and physiology (the science of\nfunctions) as the two chief divisions of scientific work. The special\nmethods and means of observation differ entirely in the two sections.\nIn morphology the work of description and comparison is the most\nimportant as regards both outer form and inner structure. In physiology\nthe exact methods of physics and chemistry are especially demanded--the\nobservation of vital activities and the attempt to discover the\nphysical laws that govern them. As a correct knowledge of human anatomy\nand physiology is indispensable for scientific medicine, and the work\nrequires a particularly large apparatus, these two sciences have long\nbeen studied separately, and have been handed over to the medical\nfacility in the division of the academic curriculum.\n\nThe broad field of morphology may be divided into anatomy and\nbiogeny; the one deals with the fully developed, and the other\nwith the developing, organism. Anatomy, the study of the formed\norganism, studies both the external form and the inner structure.\nWe may distinguish as its two branches the science of structures\n(tectology) and the science of fundamental forms (promorphology).\nTectology investigates the features of the structure in the organic\n_individual_, and the composition of the body out of various parts\n(cells, tissues, and organs). Promorphology describes the real form of\nthese individual parts and of the whole body, and endeavors to reduce\nthem mathematically to certain fundamental forms (chapter viii.).\nBiogeny, or the science of the evolution of organisms, is also divided\ninto two parts--the science of the individual (ontogeny) and of the\nstem or species (phylogeny); each follows its own peculiar methods\nand aims, but they are most intimately connected by the biogenetic\nlaw. Ontogeny deals with the development of the individual organism\nfrom the beginning of its existence to death; as embryology it\nobserves the growth of the individual within the f\u0153tal membranes;\nand as metamorphology (or the science of metamorphoses) it follows\nthe subsequent changes in post-f\u0153tal life (chapter xvi.). The\ntask of phylogeny is to trace the evolution of the organic stem or\nspecies--that is to say, of the chief divisions in the animal and\nplant worlds, which we describe as classes, orders, etc.; in other\nwords, it traces the genealogy of species. It relies on the facts of\npaleontology, and fills up the gaps in this by comparative anatomy and\nontogeny.\n\nThe science of the vital phenomena, which we call physiology, is for\nthe most part the physiology of work, or ergology; it investigates\nthe functions of the living organism, and has to reduce them as\nclosely as possible to physical and chemical laws. Vegetable ergology\ndeals with what are called the vegetative functions, nutrition and\nreproduction; animal ergology studies the animal activities of movement\nand sensation. Psychology is directly connected with the latter.\nBut the study of the relations of the organism to its environment,\norganic and inorganic, also belongs to physiology in the wider sense;\nwe call this part of it perilogy, or the physiology of relations. To\nthis belong chorology, or the science of distribution (also called\nbiological geography, as it deals with geographical and topographical\ndistribution), and \u0153cology or bionomy (also recently called\nethology), the science of the domestic side of organic life, of the\nlife-needs of organisms and their relations to other organisms with\nwhich they live (biocenosis, symbiosis, parasitism).\n\nTHIRD TABLE\n\nSYNOPSIS OF THE CHIEF BRANCHES OF BIOLOGY (1869)\n\nBIOLOGY = THE SCIENCE OF LIFE\n\n The four chief branches of systematic biology.\n\n I. Protistology = the science of single cells--unicellular organisms.\n II. Botany = the science of plants--tissue plants (metaphyta).\n III. Zoology = the science of animals--tissue animals (metazoa).\n IV. Anthropology = the science of man--speaking primates.\n\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n \u2502 A. MORPHOLOGY = THE SCIENCE OF FORMS. \u2502\n \u2502 Anatomy and biogeny of organisms. \u2502\n \u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2524\n \u2502A I. ANATOMY. \u2502A II. BIOGENY. \u2502\n \u2502The science of structure. \u2502The science of development. \u2502\n \u25021. TECTOLOGY. \u25023. PHYLOGENY. \u2502\n \u2502The science of structure. \u2502Stem history. \u2502\n \u2502Cytology, science of cells. \u2502Paleontology and genealogy. \u2502\n \u2502Histology, science of tissues. \u2502Transformism or theory of descent.\u2502\n \u2502Organology, science of organs. \u2502Natural classification. \u2502\n \u2502Blastology, science of persons. \u2502 \u2500\u2500\u2500\u2500 \u2502\n \u2502Kormology, science of trunks. \u2502 \u2502\n \u2502 \u2500\u2500\u2500\u2500 \u25024. ONTOGENY. \u2502\n \u25022. PROMORPHOLOGY. \u25024_a_. Embryology. \u2502\n \u2502The science of fundamental \u2502(Development within the \u2502\n \u2502forms. Knowledge of the geometrical \u2502f\u0153tal membranes.) \u2502\n \u2502ideal forms (mathematically \u25024_b_. Metamorphology. \u2502\n \u2502definable) in relation \u2502(Modification of the organism \u2502\n \u2502to the concrete real form of \u2502after f\u0153tal life.) \u2502\n \u2502the individual. \u2502 \u2502\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n \u2502 B. PHYSIOLOGY = THE SCIENCE OF FUNCTIONS. \u2502\n \u2502 Physics and chemistry of the organism. \u2502\n \u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2524\n \u2502B I. ERGOLOGY. \u2502B II. PERILOGY. \u2502\n \u2502 Physiology of work. \u2502Physiology of relations. \u2502\n \u25025. Vegetal ergology. \u25027. Chorology. \u2502\n \u2502Physiology of the vegetative \u2502The science of distribution. \u2502\n \u2502functions. \u2502Biological geography and topography.\u2502\n \u25025_a_. Trophonomy. \u2502The science of migrations. \u2502\n \u2502The science of metabolism. \u2502 \u2502\n \u25025_b_. Gonimatology. \u2502 \u2500\u2500\u2500\u2500 \u2502\n \u2502The science of reproduction. \u2502 \u2502\n \u2502 \u2500\u2500\u2500\u2500 \u2502 \u2502\n \u25026. Animal ergology. \u25028. \u0152COLOGY. \u2502\n \u25026_a_. Phoronomy. \u2502(or bionomy or ethology). \u2502\n \u2502The science of movement. \u2502The science of domestic life. \u2502\n \u25026_b_. Sensonomy. \u2502Biological economy. \u2502\n \u2502The science of sensation. \u2502Relations of the organism to \u2502\n \u25026_c_. Psychology. \u2502the environment, and to other \u2502\n \u2502 \u2502organisms with which it lives. \u2502\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n\n\n\n\nV\n\nDEATH\n\n Life and death--Individual death--Immortality\n of the unicellulars--Death of the protists and\n tissue-organisms--Causes of physiological death--Using up\n of the plasma--Regeneration--Biotonus--Perigenesis of the\n plastidules: memory of the biogens--Regeneration of protists and\n tissue-organisms--Senile debility--Disease--Necrobiosis--The lot\n of death--Providence--Chance and fate--Eternal life--Optimism\n and pessimism--Suicide and self-redemption--Redemption from\n evil--Medicine and philosophy--Maintenance of life--Spartan selection.\n\n\nNothing is constant but change! All existence is a perpetual flux\nof \"being and becoming\"! That is the broad lesson of the evolution\nof the world, taken as a whole or in its various parts. Substance\nalone is eternal and unchangeable, whether we call this all-embracing\nworld-being Nature, or Cosmos, or God, or World-spirit. The law of\nsubstance teaches us that it reveals itself to us in an infinite\nvariety of forms, but that its essential attributes, matter and\nenergy, are constant. All individual forms of substance are doomed\nto destruction. That will be the fate of the sun and its encircling\nplanets, and of the organisms that now people the earth--the fate\nof the bacterium and of man. Just as the existence of every organic\nindividual had a beginning, it will also undeniably have an end. Life\nand death are irrevocably united. However, philosophers and biologists\nhold very different views as to the real causes of this destiny. Most\nof their opinions are at once out of court, because they have not a\nclear idea of the nature of life, and so can have no adequate idea of\nits termination--death.\n\nThe inquiry into the nature of organic life which we instituted\nin the second chapter has shown us that it is, in the ultimate\nanalysis, a chemical process. The \"miracle of life\" is in essence\nnothing but the metabolism of the living matter, or of the plasm.\nRecent physiologists, especially Max Verworn and Max Kassowitz, have\npointed out, in opposition to modern vitalism, that \"life consists\nin a continuous alternation between the upbuild and the decay of the\nhighly complicated chemical unities of the protoplasm. And if this\nconception is admitted, we may rightly say that we know what we mean\nby death. If death is the cessation of life, we must mean by that the\ncessation of the alternation between the upbuild and the dissolution\nof the molecules of protoplasm; and as each of the molecules of\nprotoplasm must break up again shortly after its formation, we have in\ndeath to deal only with the definite cessation of reconstruction in\nthe destroyed plasma-molecules. Hence a living thing is not finally\ndead--that is to say, absolutely incompetent to discharge any further\nvital function--until the whole of its plasma-molecules are destroyed.\"\nIn the exhaustive justification with which Kassowitz follows up this\ndefinition in the fifteenth chapter of his _General Biology_, the\nnatural causes of physiological death are fully described.\n\nAmong the numerous and contradictory views of recent biologists on\nthe nature of death we find many errors and misunderstandings, due\nto a lack of clear distinction between the duration of the living\nmatter in general and that of the individual life-form. This is\nparticularly noticeable in the contradictory views which have been\nelicited by August Weismann's theory (1882) of the immortality of the\nunicellulars. I have shown in the eleventh chapter of the _Riddle_ that\nit is untenable. But as the distinguished zoologist has again taken\nup his theory with energy in his instructive _Lectures on the Theory\nof the Descent_ (1902), and has added to it erroneous observations on\nthe nature of death, I am obliged to return to the point. Precisely\nbecause this interesting work gives most valuable support to the\ntheory of evolution, and maintains Darwin's theory of selection and\nits consequences with great effect, I feel it is necessary to point\nout considerable weaknesses and dangerous errors in it. The chief of\nthese is the important theory of the germ-plasm and the consequent\nopposition to the inheritance of acquired characteristics. Weismann\ndeduces from this a radical distinction between the unicellular and\nthe multicellular organisms. The latter alone are mortal, the former\nimmortal; \"between the unicellular and the multicellular lies the\nintroduction of physiological--that is to say, normal--death.\" We\nmust say, in opposition to this, that the physiological individuals\n(_bionta_) among the protista are just as limited in their duration as\namong the histona. But if the chief stress in the question is laid,\nnot on the individuality of the living matter, but on the continuity\nof the metabolic life-movement through a series of generations, it is\njust as correct to affirm a partial immortality of the plasm for the\nmulticellulars as for the unicellulars.\n\nThe immortality of the unicellulars, on which Weismann has laid so much\nstress, can only be sustained for a small part of the protists even in\nhis own sense--namely, for those which simply propagate by cleavage,\nthe chromacea and bacteria among the monera (chapter ix.), the diatomes\nand paulotomes among the protophyta, and a part of the infusoria and\nrhizopods among the protozoa. Strictly speaking, the individual life is\ndestroyed when a cell splits into two daughter-cells. One might reply\nwith Weismann that in this case the dividing unicellular organism\nlives on as a whole in its offspring, and that we have no corpse, no\ndead remains of the living matter, left behind. But that is not true of\nthe majority of the protozoa. In the highly developed ciliata the chief\nnucleus is lost, and there must be from time to time a conjugation of\ntwo cells and a mutual fertilization of their secondary nuclei, before\nthere can be any further multiplication by simple cleavage. However,\nin most of the sporozoa and rhizopoda, which generally propagate by\nspore formation, only one portion of the unicellular organism is used\nfor this; the other portion dies, and forms a \"corpse.\" In the large\nrhizopods (thalamophora and radiolaria) the spore-forming inner part,\nwhich lives on in the offspring, is smaller than the decaying outer\nportion, which becomes the corpse.\n\nWeismann's view of the secondary \"introduction of physiological death\nin the multicellulars\" is just as untenable as his theory of the\nimmortality of the unicellulars. According to this opinion, the death\nof the histona--both the metaphyta and metazoa--is a purposive outcome\nof adaptation, only introduced by selection when the multicellular\norganism has reached a certain stage of complexity of structure, which\nis incompatible with its original immortality. Natural selection would\nthus kill the immortal and preserve only the mortal; it would interfere\nwith the multiplication of the immortals in the bloom of their years,\nand only use the mortal for rearing posterity. The curious conclusions\nwhich Weismann reached in developing this theory of death, and the\nstriking contradictions to his own theory of the germ-plasm which\nhe fell into, have been pointed out by Kassowitz in the forty-ninth\nchapter of his _General Biology_. In my opinion, this paradoxical\ntheory of death has no more basis than the germ-plasm theory he has\ningeniously connected with it. We may admire the subtlety and depth\nof the speculations with which Weismann has worked out his elaborate\nmolecular theory. But the nearer we get to its foundations the less\nsolid we find them. Moreover, not one of the many supporters of the\ntheory of germ-plasm has been able to make profitable use of it in the\ntwenty years since it was first published. On the other hand, it has\nhad an evil influence in so far as it denied the inheriting of acquired\ncharacters, which I hold, with Lamarck and Darwin, to be one of the\nsoundest and most indispensable supports of the theory of descent.\n\nIn discussing the question of the real causes of death, we confine our\nattention to normal or physiological death without considering the\ninnumerable causes of accidental or pathological death, by illness,\nparasites, mishaps, etc. Normal death takes place in all organisms when\nthe limit of the hereditary term of life is reached. This limit varies\nenormously in different classes of organisms. Many of the unicellular\nprotophyta and protozoa live only a few hours, others several months\nor years; many one-year plants and lower animals live only a summer in\nour temperate climate, and only a few weeks or months in the arctic\ncircle or on the snow-covered Alps. On the other hand, the larger\nvertebrates are not uncommonly a hundred years old, and many trees live\nfor a thousand years. The normal span of life has been determined in\nall species in the course of their evolution by adaptation to special\nconditions, and has then been transmitted to offspring by heredity. In\nthe latter, however, it is often subject to considerable modifications.\n\nThe organism has been compared, on the modern \"machine theory\" of life,\nto an artificially constructed mechanism, or an apparatus in which the\nhuman intelligence has put together various parts for the attainment of\na certain end. This comparison is inapplicable to the lowest organisms,\nthe monera, which are devoid of such a mechanical structure. In these\nprimitive \"organisms without organs\" (chromacea and bacteria) the sole\ncause of life is the invisible chemical structure of the plasm and the\nmetabolism effected by this. As soon as this ceases death takes place\n(_cf._ chapter ix.). In the case of all other organisms the comparison\nis useful in so far as the orderly co-operation of the various organs\nor parts accomplishes a certain task by the conversion of virtual\ninto active force. But the great difference between the two is that\nin the case of the machine the regularity is due to the purposive and\nconsciously acting will of man, whereas in the case of the organism it\nis produced by unconscious natural selection without any design. On\nthe other hand, the two have another important feature in common in\nthe limited span of life which is involved in their being used up. A\nlocomotive, ship, telegraph, or piano, will last only a certain number\nof years. All their parts are worn out by long use, and, in spite of\nall repairing, become at last useless. So in the case of all organisms,\nthe various parts are sooner or later worn out and rendered useless;\nthis is equally true of the organella of the protist and the organs of\nthe histon. It is true that the parts may be repaired or regenerated;\nbut sooner or later they cease to be of service, and become the cause\nof death.\n\nWhen we take the idea of regeneration, or the recuperation of parts\nthat have been rendered useless, in the widest sense, we find it to\nbe a universal vital function of the greatest importance. The whole\nmetabolism of the living organism consists in the assimilation of\nplasm, or the replacing of the plasma-particles which are constantly\nused up by dissimilation (_cf._ chapter x.). Verworn has given the name\nof _biogens_ to the hypothetical molecules of living matter--which\nI regard with Hering as endowed with memory, and (1875) have called\nplastidules. He says: \"The biogens are the real vehicles of life.\nIn their constant decay and reconstruction consists the process of\nlife, which expresses itself in the great variety of vital phenomena.\"\nThe relation of assimilation (the building-up of the biogens) to\ndissimilation (the decay of the biogens) may be expressed by a fraction\nto which the name _biotonus_ is given A/D. It is of radical importance\nin the various phenomena of life. The variations in the size of this\nfraction are the cause of all change in the life-expression of every\norganism. When the biotone increases, and the metabolism quotient\nbecomes more than one, we have growth; when, on the other hand, it\nfalls below one, and the biotone decreases, we have atrophy, and\nfinally death. New biogens are constructed in _regeneration_. In\n_generation_ or reproduction groups of biogens (as germ-plasm) are\nreleased from the parent in consequence of redundant growth, and form\nthe foundation of new individuals.\n\nThe phenomena of regeneration are extremely varied, and have of\nlate years been made the subject of a good deal of comprehensive\nexperiment, especially on the side of what is called \"mechanical\nembryology.\" Many of these experimental embryologists have drawn\nfar-reaching conclusions from their somewhat narrow experiments, and\nhave partly urged them as objections to Darwinism. They imagine that\nthey have disproved the theory of selection. Most of these efforts\nbetray a notable lack of general physiological and morphological\nknowledge. As they also generally ignore the biogenetic law, and\ntake no account of the fundamental correlation of embryology and\nstem history, we can hardly wonder that they reach the most absurd\nand contradictory conclusions. Many examples of this will be found\nin the _Archiv f\u00fcr Entwickelungsmechanik_. When, however, we make\na comprehensive survey of the interesting field of regeneration\nprocesses, we discover a continuous series of development from\nthe simplest repair of plasm in the unicellular protists to the\nsexual generation of the higher histona. The sperm-cells and ova\nof the latter are redundant growth-products, which have the power\nof regenerating the whole multicellular organism. But many of the\nhigher histona have also the capacity to produce new individuals by\nregeneration from detached pieces of tissue, or even single cells.\nIn the peculiar mode of metabolism and growth which accompanies\nthese processes of regeneration, the memory of the plastidule, or\nthe unconscious retentive power of the biogens, plays the chief part\n(_cf._ my _Perigenesis of the Plastidule_, 1875). In the most primitive\nkinds of the unicellular protists we find the phenomena of death and\nregeneration in the simplest form. When an unnucleated moneron (a\nchromaceum or bacterium) divides into two equal halves, the existence\nof the dividing individual comes to an end. Each half regenerates\nitself in the simplest conceivable way by assimilation and growth,\nuntil it, in turn, reaches the size of the parent organism. In the\nnucleated cells of most of the protophyta and protozoa it is more\ncomplicated, as the nucleus becomes active as the central organ and\nregulator of the metabolism. If an infusorium is cut into two pieces,\nonly one of which contains the nucleus, this one alone grows into a\ncomplete nucleated cell; the unnucleated portion dies, being unable to\nregenerate itself.\n\nIn the multicellular body of the tissue-forming organisms we must\ndistinguish between the partial death of the various cells and the\ntotal death of the whole organism, or cell-state, which they make up.\nIn many of the lower tissue-plants and tissue-animals the communal\nlink is very loose and the centralization slight. Odd cells or groups\nof cells may be set loose, without any danger to the life of the\nwhole histon, and grow into new individuals. In many of the alg\u00e6\nand liverworts (even in the _bryophyllum_, closely related to the\nstone-crop, or _sedum_)--as well as in the common fresh-water polyp,\nhydra, and other polyps--every bit that is cut off is capable of\ngrowing into a complete individual. But the higher the organization\nis developed and the closer the correlation of the parts and their\nco-operation in the life of the centralized stock or person, the\nslighter we find the regenerative faculty of the several organs. Even\nthen, however, many used-up cells may be removed and replaced by\nregenerated new cells. In our own human organism, as in that of the\nhigher animals, thousands of cells die every day, and are replaced\nby new cells of the same kind, as, for instance, epidermic cells at\nthe surface of the skin, the cells of the salivary glands or the\nmucous lining of the stomach, the blood-cells, and so on. On the other\nhand, there are tissues that have little or nothing of this repairing\npower, such as many of the nerve-cells, sense-cells, muscle-cells,\netc. In these cases a number of constant cell-individuals remain with\ntheir nucleus throughout life, although a used-up portion of their\ncell-body may be replaced by regeneration from the cytoplasm. Thus\nour human body, like that of all the higher animals and plants, is a\n\"cell-state\" in another sense. Every day, nay, every hour, thousands\nof its citizens, the tissue-cells, pass away, and are replaced by\nothers that have arisen by cleavage of similar cells. Nevertheless,\nthis uninterrupted change of our personality is never complete or\ngeneral. There is always a solid groundwork of conservative cells, the\ndescendants of which secure the further regeneration.\n\nMost organisms meet their death through external or accidental\ncauses--lack of sufficient food, isolation from their necessary\nenvironment, parasites and other enemies, accidents and disease. The\nfew individuals who escape these accidental causes of death find the\nend of life in old age or senility, by the gradual decay of the organs\nand dwindling of their functions. The cause of this senility and the\nensuing natural death is determined for each species of organisms by\nthe specific nature of their plasm. As Kassowitz has lately pointed\nout, the senility of individuals consists in the inevitable increase\nin the decay of protoplasm and the metaplastic parts of the body\nwhich this produces. Each metaplasm in the body favors the inactive\nbreak-up of protoplasm, and so also the formation of new metaplasms.\nThe death of the cells follows, because the chemical energy of the\nplasm gradually falls off from a certain height, the acme, of life.\nThe plasm loses more and more the power to replace by regeneration the\nlosses it sustains by the vital functions. As, in the mental life, the\nreceptivity of the brain and the acuteness of the senses gradually\ndecay, so the muscles lose their energy, the bones become fragile, the\nskin dry and withered, the elasticity and endurance of the movements\ndecrease. All these normal processes of senile decay are caused by\nchemical changes in the plasm, in which dissimilation gains constantly\non assimilation. In the end they inevitably lead to normal death.\n\nWhile the gradual decay of the bodily forces and the senile\ndegeneration of the organs must necessarily cause the death of the\nsoundest organism in the end, the great majority of men pass away\nthrough illness long before this normal term of life is reached. The\nexternal causes of this are the attacks of enemies and parasites,\naccidents, and unfavorable conditions of life. These cause changes\nin the tissues and their component cells, which first occasion the\npartial death of particular sections, and then the total death of the\nwhole individual. The modifications of the living matter which produce\ndisease and premature death are called _necrobioses_. They consist\npartly of _histolyses_--that is to say, degeneration of the cells by\natrophy, dissolution, withering (mortification), or colliquation; and\npartly of _metaplasmosisms_, or metamorphoses of the plasm--fatty,\nmucous, chalky, or amyloid metamorphoses of the cells. It was the great\nmerit of Rudolph Virchow that he proved, in his epoch-making _Cellular\nPathology_ (1858), that all diseases in man and other organisms may be\nreduced to such modifications of the cells which make up the tissues.\nHence disease, with its pain, is a physiological process, a life under\ninjurious and dangerous conditions. As in all normal vital phenomena,\nso in abnormal or pathological, the ultimate ground must be sought in\nthe physical and chemical processes in the plasm. Pathology is a part\nof physiology. This discovery has cut the ground from under the older\nnotion of disease as a special entity, a devil, or a divine punishment.\n\nThe natural physical explanation of death, which has been made possible\nby modern physiology and pathology, has shattered, not only all the\nold superstitious ideas about disease and death, but also a number of\nimportant metaphysical dogmas which built upon them. Such was, for\ninstance, the na\u00efve belief in a conscious Providence, controlling\nthe fate of individuals and determining their death. I do not fail\nto appreciate the great subjective value which such a trust in a\nprotecting Providence has for men amid their countless dangers. We may\nenvy the childish temper for the confidence and hope which it derives\nfrom this belief. But as we do not seek to have our emotions gratified\nby poetic fictions, we are bound to point out that reason cannot detect\nthe shadow of a proof of the existence and action of this conscious\nProvidence, or \"loving Father in heaven.\" We read daily in our journals\nof accidents and crimes of all kinds that cause the unexpected death\nof happy human beings. Every year we read with horror the statistics\nof the thousands of deaths from shipwreck and railway accidents,\nearthquakes and landslips, wars and epidemics. And then we are asked\nto believe in a loving Providence that has decreed the death of each\nof these poor mortals! We are asked to console ourselves in face of\nthe tragedy with the hollow phrases: \"God's will be done,\" or \"God's\nways are wonderful.\" Simple children and dull believers may soothe\nthemselves with such phrases. They no longer impose on educated people\nin the twentieth century, who prefer a full and fearless knowledge of\nthe truth.\n\nWhen our monistic and rational conception of death is described as\ndreary and hopeless, we may answer that the prevalent dualistic view is\nmerely an outcome of hereditary habits of thought and mystic training\nin early youth. When these are displaced by progressive culture and\nscience, it will be clear that man has lost nothing, but gained much,\nas regards his life on earth. Convinced that there is no eternal life\nawaiting him, he will strive all the more to brighten his life on\nearth and rationally improve his condition in harmony with that of his\nfellows. If it is objected that then everything will depend on mere\n\"chance,\" instead of being controlled by a conscious Providence or a\nmoral order of the world, I must refer the reader for my reply to the\nclose of the fourteenth chapter of the _Riddle_, where I have dealt\nwith fate, providence, end, aim, and chance. And if it is further\nclaimed that our realistic view of life leads to pessimism, there is no\nbetter ground for such an accusation.\n\nI have given, in the eleventh chapter of the _Riddle_, the scientific\nreasons which forbid us to accept the personal immortality of the soul.\nBut as the most vehement attacks have been made on this chapter by\nmetaphysicians of the prevailing school and by Christian theologians,\nI must return to the question here. I am convinced, from numbers of\nletters I have received and conversation with educated people of all\nclasses, that no other dogma is so firmly established and highly valued\nas athanatism, or the belief in personal immortality. Most men will not\ngive up at any price the hope that a better life awaits them beyond\nthe grave, which will compensate them for all the pain and suffering\nthey endure here. In the picturing of this future life the medi\u00e6val\ngeocentric idea still forms the chief feature. Troelslund has shown, in\nhis _Idea of Heaven and of the World_, how this theory still dominates\nthe metaphysics of the majority of men; in spite of Copernicus and\nLaplace, heaven is still for most people the semicircular blue glass\nbell that overarches the earth. We still hear the praises of our life\nin this heaven sung daily in sermons and speeches and festive orations.\nThe orator extends his right hand \"upward\" to the infinite starry\nspace of heaven, forgetting that the radius of the direction he is\npointing towards changes every second, and in twelve hours reaches the\nprecisely opposite direction, and becomes \"downward.\" Other believers\nendeavor to be still more concrete, and point out definite celestial\nbodies as the homes of immortal souls. Modern cosmology, astronomy, and\ngeology entirely exclude these pretty fictions from science; and modern\npsychology, physiology, ontogeny, and phylogeny rigorously refuse an\ninch of ground for athanatism.\n\nOptimism regards the world on its good and bright and admirable\nside: pessimism looks to the shades and tragedies of life. In some\nphilosophic and religious systems one or other of these tendencies\nis consistently and exclusively worked out; but in most systems the\ntwo are mingled. Pure and consistent realism is generally neither\noptimistic nor pessimistic. It takes the world as it is, a unified\nwhole, the nature of which is neither good nor bad. Dualistic idealism,\nhowever, generally combines the two, and distributes them between\nits two worlds; it describes this world as a \"vale of tears,\" and\nthe next as a glorious city of joy and happiness. This view is a\nconspicuous feature in most of the dualistic religions, and has still\na considerable influence, both practically and theoretically, on the\nminds of educated people.\n\nThe founder of systematic optimism was Gottfried Leibnitz, whose\nphilosophy sought to achieve an ingenious harmony between divergent\nsystems, but is really a form of dynamism, or a monism somewhat akin to\nthe energism of Ostwald. Leibnitz gave a compendious statement of his\nsystem in his _Monadology_ (1714). He taught that the world consists of\nan infinite number of monads (which almost correspond to our psychic\natoms), but this pluralism was converted into a monism by making God,\nas the central monad, bind all together in a substantial unity. In\nhis _Theodicy_ (1710) he taught that God (the \"all-wise, all-good,\nand almighty creator of the world\") had with perfect consciousness\ncreated \"the best of all possible worlds\"; that his infinite goodness,\nwisdom, and power are seen everywhere in the pre-established harmony\nof things; but that the individual human being, and humanity taken as\na whole, have only a limited capacity for development. The man who\nknows the real features of the world, who has honestly confronted the\ntragic struggle for life that rules throughout living nature, who has\nsympathy for the infinite sum of misery and want of every kind in the\nlife of men, can scarcely understand how an acute and informed thinker\nlike Leibnitz could entertain such optimism as this. It would be more\nintelligible in the case of a one-sided and nebulous metaphysician like\nHegel, who held that \"all that is real is rational and all that is\nrational is real.\"\n\nPessimism is the direct opposite of systematic optimism. While the\none holds the universe to be the best, the other regards it as the\nworst, of all possible worlds. This pessimistic conception has found\nexpression in the oldest and most popular religions of Asia, Brahmanism\nand Buddhism. Both these Hindoo religions were originally pessimistic,\nand at the same time atheistic and idealistic. Schopenhauer especially\npointed out this, declaring that they were the most perfect of all\nreligions, and importing their leading ideas into his own system. He\nconsiders it \"a glaring absurdity to attempt to prove this miserable\nworld the best of all possible ones--this cock-pit of tortured and\nsuffering beings, who can only survive by destroying one another, in\nwhich the capacity for pain grows with knowledge, and so reaches its\nheight in man. Truly optimism cuts so sorry a figure in this theatre of\nsin, suffering, and death that we should have to regard it as a piece\nof sarcasm if Hume had not given us an explanation of its origin (the\nwish to flatter God and hope for some result from it). To the palpable\nsophistry of Leibnitz, who would prove this world the best of all\npossible, we can oppose a strict and honest proof that it is the worst\nof all possible.\" However, neither Schopenhauer nor the most important\nof modern pessimists, Edward Hartmann, has drawn the strict practical\nconclusion from pessimism. That would be to deny the will to live, and\nput an end to suffering by suicide.\n\nThe mention of suicide as the logical consequence of pessimism may\nserve as an occasion to glance at the curious and contradictory views\nthat are expressed about it. There are few problems of life (apart\nfrom immortality and the freedom of the will) on which such absurd\nand contradictory things have been said even down to our own time.\nThe theist who regards life as a gift of God may hesitate to reject\nor return it--although the offering of one's self as a victim for\nother men is considered a high virtue. Most educated people still look\nupon suicide as a great sin, and in some countries (such as England)\nthe attempt is punished by law. In the Middle Ages, when a hundred\nthousand men were burned alive for heresy or witchcraft, suicides\nwere punished by a disgraceful burial. As Schopenhauer says: \"Clearly\nthere is nothing in the world to which a man has a plainer right than\nhis own life and person. It is simply ridiculous for criminal justice\nto deal with suicide.\" The advance of embryology in the last thirty\nyears has made it clear that the individual life of a man (and all\nother vertebrates) begins at the moment when the male sperm-cell and\nthe maternal ovum coalesce. In this blind chance plays an important\npart, as in so many other important aspects of life--taking \"chance\"\nin the scientific sense, which I have explained in chapter xiv. of\nthe _Riddle_. Hence, the real cause of personal existence is not the\nfavor of the Almighty, but the sexual love of one's earthly parents;\nvery often this consequence of the act of love has been anything but\ndesired. If, then, the circumstances of life come to press too hard\non the poor being who has thus developed, without any fault of his,\nfrom the fertilized ovum--if, instead of the hoped-for good, there\ncome only care and need, sickness and misery of every kind--he has the\nunquestionable right to put an end to his sufferings by death. Every\nreligion assents to this under certain conditions, even Christianity\nwhen it says: \"If thine eye scandalize thee, cast it from thee.\" It\nis true that the conventional morality condemns suicide under any\ncircumstances; but the reasons it alleges are ridiculously slight, and\nare not improved by having the mantle of religion wrapped about them.\n\nThe voluntary death by which a man puts an end to intolerable suffering\nis really an act of redemption. We should, therefore, describe it as\nself-redemption, and look on it with Christian sympathy, not brand it\npharisaically as \"self-murder.\" As a fact, this contemptuous phrase\nhas no meaning, since murder is the taking away of a man's life against\nhis will, while the suicide dies voluntarily. Hence, he usually\ndeserves our sympathy, not contempt, and certainly not punishment.\nOur conventional morality is, as so often happens, full of senseless\ncontradictions. Modern states have introduced conscription; they demand\nthat every citizen shall give up his life for his country on command,\nand kill as many other men as he can (an admirable commentary on the\nScriptural \"Love your enemies\") for some political reason or other.\nBut they never secure to each citizen the means of honorable existence\nand free development of his personality--not even the right to work by\nwhich he may maintain himself and his family.\n\nI fully recognize the advance that social politics has made in\nimproving the conditions of the poorer classes, the promotion of\nhygiene and education and the bodily and mental welfare of citizens;\nbut we are still very far from the attainable ideal of general\nprosperity and happiness which reason dictates to every civilized\nnation. Misery and want are increasing among the poor, as the division\nof labor and over-population increase. Thousands of strong and active\nmen come to grief every year without any fault of theirs, often\nprecisely because they were quiet and honest; thousands are hungry\nbecause, with the best will in the world, they cannot find work;\nthousands are sacrificed to the heartless demands of our iron age of\nmachinery with its exacting technical and industrial requirements. On\nthe other hand, we see thousands of contemptible characters prospering\nbecause they have been able to deceive their fellows by unscrupulous\nspeculations, or because they have flattered and served the higher\nauthorities. It is no wonder that the statistics of suicide increase so\nmuch in the more civilized communities. No feeling man who has any real\n\"Christian love of his neighbor\" will grudge his suffering brother the\neternal rest and the freedom from pain which he has obtained by his\nself-redemption.\n\nThe seventh petition of the Lord's Prayer, which is repeated daily by\nmillions of Christians, is: \"Deliver us from evil.\" Luther explains\nthis as a prayer to be saved \"from all evil of body and soul\" in\nthis life and the next. When we consider this in the light of our\nmonistic principles, we have naturally to set aside the superstitious\nideas of the Middle Ages regarding the future life, and deal only\nwith the petition as regards this life. The number and variety and\ngravity of these evils have grown in civilized communities in the\nnineteenth century, notwithstanding all the progress we have made in\nart and science and the rational reform of our personal and social\nlife. Civilization has gained infinitely in value by the change we\nhave made in our conceptions of time and space in this age of steam\nand electricity. We can make our domestic and public life much\npleasanter, and avail ourselves of a far greater number of luxuries,\nthan was possible to our grandfathers a hundred years ago. But all\nthis has caused a much greater expenditure of nerve-energy. The brain\nhas to bear a much greater strain, and is worn out earlier, the body\nis more stimulated and overworked than it was a hundred years ago.\nMany diseases of modern civilization are making appalling progress;\nneurasthenia, especially, and other diseases of the nerves, carry off\nmore victims every year. Our asylums grow bigger and more numerous\nevery year, and we have sanatoria on every side in which the baited\nvictim of modern civilization seeks refuge from his evils. Some of\nthese evils are quite incurable, and the sufferers have to meet a\ncertain death in terrible pain. Many of these poor creatures look\nforward to their redemption from evil and the end of their miserable\nlives. The important question arises whether, as compassionate men,\nwe should be justified in carrying out their wish and ending their\nsufferings by a painless death.\n\nThis question is of great importance, both in practical philosophy\nand in juridical and medical practice, and, as opinions differ very\nmuch on the subject, it seems advisable to deal with it here. I start\nfrom my own personal opinion, that sympathy is not only one of the\nnoblest and finest functions of the human brain, but also one of\nthe first conditions of the social life of the higher animals. The\nprecepts of Christian charity which the gospels rightly place in the\nvery foreground of morality, were not first discovered by Christ, but\nthey were successfully urged by him and his followers at a time when\nrefined selfishness threatened the Roman civilization with decay.\nThese natural principles of sympathy and altruism had arisen thousands\nof years before in human society, and are even found among all the\nhigher animals that live a social life. They have their first roots\nin the sexual reproduction of the lower animals, the sexual love and\nthe care of the young on which the maintenance of the species depends.\nHence the modern prophets of pure egoism, Friedrich Nietzsche, Max\nStirner, etc., commit a biological error when they would substitute\ntheir morality of the strong for universal charity, and when they\nridicule sympathy as a weakness of character or an ethical blunder\nof Christianity. It is just in its insistence on sympathy that the\nChristian teaching is most valuable, and this part of its system\nwill survive long after its dogmas have sunk into oblivion. However,\nthis lofty duty must not be confined to men, but extended to \"our\nrelations,\" the higher vertebrates, and, in fact, to all animals whose\nbrain-organization seems to point to the possession of sensation and\na consciousness of pleasure and pain. Thus, for instance, in the case\nof the domestic animals which we use daily in our service, and which\nhave an undoubted psychic affinity to ourselves, we must take care\nto increase their pleasures and mitigate their sufferings. Faithful\ndogs and noble horses, with which we have lived for years and which\nwe love, are rightly put to death and relieved from pain when they\nfall hopelessly ill in old age. In the same way we have the right, if\nnot the duty, to put an end to the sufferings of our fellow-men. Some\nsevere and incurable disease makes life unbearable for them, and they\nask for redemption from evil. However, medical men hold very different\nopinions on the matter, as I have found in conversation with them.\nMany experienced physicians, who practise their profession in a spirit\nof sympathy and without dogmatic prejudice, have no scruple about\ncutting short the sufferings of the incurable by a dose of morphia or\ncyanide of potassium when they desire it; very often this painless\nend is a blessing both to the invalids and their families. However,\nother physicians and most jurists are of opinion that this act of\nsympathy is not right, or is even a crime; that it is the duty of the\nphysician to maintain the life of his patients as long as he can in all\ncircumstances. I should like to know why.\n\nWhile I am dealing with this important and--for the medical\nconscience--difficult question of social ethics, I may take the\nopportunity to consider the general attitude of physicians to the\nmonistic philosophy. It is now half a century since I visited the\nwards in the Julius hospital at W\u00fcrtzburg as a medical student. It is\ntrue that--happily for me and my patients!--I practised the profession\nonly for a short time after I had passed my examinations in 1857;\nbut the thorough acquaintance with the human organism, its anatomic\nstructure and physiological functions, which I then obtained has been\nof incalculable service to me. I owe to it not only the solid empirical\nfoundation of the special study of my life, zoology, but also the\nmonistic tendency of my whole system. As the medical training in its\nwidest sense includes anthropology--and so should include psychology\nalso--its value for speculative philosophy cannot be exaggerated. The\nscholastic metaphysicians who still regard the chairs of philosophy at\nour universities as their monopoly would have avoided most of their\ndualistic errors if they had had a thorough training in human anatomy,\nphysiology, ontogeny, and phylogeny. Even pathology, the science of\nthe diseased organism, is very instructive for the philosopher. The\npsychologist especially acquires, by the study of mental disease and\nthe visiting of the asylum wards, a profound insight into the mental\nlife which no speculative philosophy could give him. There are few\nexperienced and thoughtful physicians who retain the conventional\nbelief in the immortality of the soul and God. What would the immortal\nsoul do on the other side of eternity when it is already utterly\nruined in this life, or was even born as an idiot? How can a just God\ncondemn the criminal to the fires of hell when he himself has tainted\nthe man with an hereditary bias, or has placed him in an environment\nin which, seeing the absence of free-will, crime was a necessity for\nhim? And how can this all-loving God answer for the immeasurable sum of\nwant and misery, and pain and unhappiness, which he sees accumulated\nbefore him every year in the lives of families and states, cities and\nhospitals? It is no wonder that the old saying ran: _Ubi tres medici,\nduo sunt athei_ (Of three doctors two are sure to be atheists). One\nof my medical colleagues was an old, experienced, and sympathetic\nphysician who had travelled all over the world, and had then, as\ndirector of a large hospital, been a close witness of the sufferings of\nhumanity. Religiously educated by pious parents, and endowed with keen\nsensitiveness, he was, after long struggles, forced by his medical\nstudies to part with the faith of his boyhood--like myself, in his\ntwenty-first year. We were talking about the great mysteries of life\nshortly before his death, and he said to me: \"I have been unable to\nreconcile belief in the immortality of the soul and the freedom of the\nwill with my psychological experiences, and I have been just as unable\nto discover throughout the whole world a single trace of a moral order\nor a beneficent providence. If it is true that an intelligent Deity\nrules the world, he cannot be a God of love, but an all-powerful demon,\nwhose constant entertainment is an eternal and merciless play of being\nand becoming, building up and destroying.\" However, we do still find\nhere and there informed and intelligent physicians who adhere to the\nthree central dogmas of metaphysics--a proof of the immense power of\ndogmatic tradition and religious prejudice.\n\nWe must class as a traditional dogma the wide-spread belief that\nman is bound under all circumstances to maintain and prolong life,\neven when it has become utterly useless--a source of pain to the\nincurable and of endless trouble to his friends. Hundreds of thousands\nof incurables--lunatics, lepers, people with cancer, etc.--are\nartificially kept alive in our modern communities, and their sufferings\nare carefully prolonged, without the slightest profit to themselves or\nthe general body. We have a strong proof of this in the statistics of\nlunacy and the growth of asylums and nerve-sanatoria. In Prussia alone\nthere were 51,048 lunatics cared for in the asylums (six thousand in\nBerlin) in 1890; more than one-tenth of them were quite incurable (four\nthousand of them suffering from paralysis). In France, in 1871, there\nwere 49,589 in the asylums (or 13.8 per thousand of the population),\nand in 1888 there were 70,443 (or 18.2 per thousand); thus, in the\ncourse of seventeen years, the absolute number of the unsound rose\nnearly 30 per cent. (29.6), while the total population only increased\n5.6 per cent. In our day the number of lunatics in civilized countries\nis, on the average, five-sixths per thousand. If the total population\nof Europe is put at three hundred and ninety to four hundred millions,\nwe have at least two million lunatics among them, and of these more\nthan two hundred thousand are incurable. What an enormous mass of\nsuffering these figures indicate for the invalids themselves, and what\na vast amount of trouble and sorrow for their families, what a huge\nprivate and public expenditure! How much of this pain and expense could\nbe spared if people could make up their minds to free the incurable\nfrom their indescribable torments by a dose of morphia! Naturally\nthis act of kindness should not be left to the discretion of an\nindividual physician, but be determined by a commission of competent\nand conscientious medical men. So, in the case of other incurables\nand great sufferers (from cancer, for instance), the \"redemption from\nevil\" should only be accomplished by a dose of some painless and rapid\npoison when they have expressed a deliberate wish (to be afterwards\njuridically proved) for this, and under the control of an authoritative\ncommission.\n\nThe ancient Spartans owed a good deal of their famous bravery, their\nbodily strength and beauty, as well as their mental energy and\ncapacity, to the old custom of doing away with new-born children who\nwere born weakly or crippled. We find the same custom to-day among\nmany savage races. When I pointed out the advantages of this Spartan\nselection for the improvement of the race in 1868 (chapter vii. of\nthe _History of Creation_) there was a storm of pious indignation in\nthe religious journals, as always happens when pure reason ventures\nto oppose the current prejudices and traditional beliefs. But I ask:\nWhat good does it do to humanity to maintain artificially and rear the\nthousands of cripples, deaf-mutes, idiots, etc., who are born every\nyear with an hereditary burden of incurable disease? Is it not better\nand more rational to cut off from the first this unavoidable misery\nwhich their poor lives will bring to themselves and their families? It\nis no use to reply that religion forbids it. Christianity also bids us\ngive up our life for our brethren, and to cast it from us when it hurts\nus--that is to say, when it only causes useless pain to us and our\nfriends. The truth is, the opposition is only due to sentiment and the\npower of conventional morality--that is to say, to the hereditary bias\nwhich is clothed in early youth with the mantle of religion, however\nirrational and superstitious be its foundation. Pious morality of this\nsort is often really the deepest immorality. \"Laws and rights creep on\nlike an eternal sickness;\" this is equally true of the social customs\nand morals on which laws and rights are founded. Sentiment should\nnever be allowed to usurp the place of reason in these weighty ethical\nquestions. As I pointed out in the first chapter of the _Riddle_,\nsentiment is a very amiable, but a very dangerous, function of the\nbrain. It has no more to do with the attainment of the truth than what\nis called revelation. That is well seen in Kant's dualism, for his\n_mundus intelligibilis_ is essentially an outcome of his religious\nsentimentality\n\n\n\n\nVI\n\nPLASM\n\n Plasm is the universal living substance--Definition of protoplasm,\n chemically and morphologically--Physical character--Viscous\n condition--Chemical analysis--Colloid character of\n albumin--Albuminoid molecules--Elementary structure of plasm--Work\n of plasm--Protoplasm and metaplasm--Structures of metaplasm--Frothy\n structure--Skeletal structure--Fibrous structure--Granular\n structure--Molecular structure--Plasma molecules--Plastidules and\n biogens--Micella and biophora--Caryoplasm and cytoplasm--Nuclear\n matter--Chromatin and achromin--Nucleolus and centrosoma--Caryotheka\n and caryolymph--Cellular matter--Plasma products--Internal plasma\n products--External plasma products--Cell membranes--Intercellular\n matter--Cuticular matter.\n\n\nBy plasm, in the widest sense of the word, we mean the living matter,\nor all bodies that are found to constitute the material foundations\nof the phenomena of life. It is usual to give this matter the name\nof protoplasm; but this older and historically important designation\nhas suffered so many changes of meaning through the variety of its\napplications that it is better now to use it only in the narrower\nsense. Moreover, recent research on protoplasm has been greatly\ndeveloped, and several new names have been invented, which are formed\nfrom the word \"plasm\" with a qualifying prefix. These are special\nvarieties of the general idea of plasm, or special modifications of the\ngeneral matter, such as metaplasm, archiplasm, and so on.\n\nThe botanist, Hugo Mohl, who first introduced the name \"protoplasm\"\nin 1846, used it to designate a part of the contents of the ordinary\nplant-cell--namely, the viscous matter that Schleiden called\n\"cell-mucus,\" which is found on the inner surface of the cell-wall,\nand often forms a varying net-work or skeleton in the watery fluid in\nthe cell, and exhibits characteristic movements. Mohl gave the name of\n\"primordial skin\" to this important wall-layer (the chief element of\nthe plant-cell), and called the material of it, as being chemically\ndifferent from the other parts of the cell, _protoplasm_--that is to\nsay, the first (_proton_) or earliest formation of the organism. It is\nimportant to notice that Mohl, the author of the name, conceived it in\na purely chemical, not a morphological, sense, like Oscar Hertwig and\nother recent cytologists. I intend to retain this early chemical idea\nof protoplasm--or, briefly, plasm. It was also taken in this sense by\nMax Schultze, who pointed out (in 1860) its extreme significance and\nwide distribution in all living cells, and introduced an important\nreform of the cell-theory which we will see later.\n\nThe mixing of the chemical and the morphological ideas of protoplasm\nhas been very mischievous in recent biology, and has led to great\nconfusion. It generally comes from a failure to formulate clearly the\ndifference between the two essential elements of the modern notion of\nthe cell--the anatomic distinction between the nucleus and the body\nof the cell. The internal nucleus (or _caryon_) had the appearance of\na solid, definite, morphologically distinct constituent of the cell;\nthe outer and softer mass which we now call the cell-body (_celleus_\nor _cytosoma_) seemed to be a formless and only chemically definable\nprotoplasm. It was only discovered at a later date that the chemical\ncomposition of the nucleus is closely akin to that of the cell-body,\nand that we may properly associate the _caryoplasm_ of the one with the\n_cytoplasm_ of the other under the general heading of _plasm_. All the\nother materials that we find in the living organism are products or\nderivatives of the active plasm.\n\nIn view of the extraordinary significance which we must assign to the\nplasm--as the universal vehicle of all the vital phenomena (or \"the\nphysical basis of life,\" as Huxley said)--it is very important to\nunderstand clearly all its properties, especially the chemical ones.\nThis is rendered somewhat difficult from the circumstance that the\nplasm is, in most of the organic cells, closely bound up with other\nsubstances--the various plasma products; it can rarely be isolated in\nits purity, and can never be had pure in any quantity. Hence we are for\nthe most part dependent on the imperfect, and often ambiguous, results\nof microscopic and microchemical research.\n\nIn every case where we have with great difficulty succeeded in\nexamining the plasm as far as possible and separating it from the\nplasma-products, it has the appearance of a colorless, viscous\nsubstance, the chief physical property of which is its peculiar\nthickness and consistency. The physicist distinguishes three conditions\nof inorganic matter--solid, fluid, and gaseous. Active living\nprotoplasm cannot strictly be described as either fluid or solid in the\nphysical sense. It presents an intermediate stage between the two which\nis best described as viscous; it is best compared to a cold jelly or\nsolution of glue. Just as we find the latter substance in all stages\nbetween the solid and the fluid, so we find in the case of protoplasm.\nThe cause of this softness is the quantity of water contained in the\nliving matter, which generally amounts to a half of its volume and\nweight. The water is distributed between the plasma molecules, or the\nultimate particles of living matter, in much the same way as it is in\nthe crystals of salts, but with the important difference that it is\nvery variable in quantity in the plasm. On this depends the capacity\nfor absorption or imbibition in the plasm, and the mobility of its\nmolecules, which is very important for the performance of the vital\nactions. However, this capacity of absorption has definite limits\nin each variety of plasm; living plasm is not soluble in water, but\nabsolutely resists the penetration of any water beyond this limit.\n\nThe chemistry of living matter is the most important and interesting,\nbut at the same time the most difficult and obscure, part of the whole\nof biological chemistry. In spite of the innumerable and careful\ninvestigations which have been made of it by the ablest physiologists\nand chemists in the second half of the nineteenth century, we are\nstill far from a satisfactory solution of this fundamental problem\nof biology. This is due partly to the extraordinary difficulty of\nisolating pure living plasm and subjecting it to chemical analysis,\nand partly to the many errors and misunderstandings that have arisen\nthrough one-sided treatment of the subject, and especially through\nconfusion of the chemical and morphological features of plasm. We can\nthus understand the contradictory views that are still put forward by\ndistinguished chemists and physiologists, zoologists and botanists.\nAs I cannot deal here with the very extensive, elaborate, and\ncontradictory literature of the subject, I must be content to give a\nbrief summary of the conclusions I have reached by my reading and my\nown studies of plasm (begun in 1859).\n\nTo begin with, we must clearly understand that protoplasm--in the most\ngeneral sense in which we here take it--is a _chemical_ substance, not\na \"mixture of different substances,\" or a \"mixture of a small quantity\nof solid matter with a good deal of fluid.\" As Richard Neumeister\nvery well observes: \"We seek the nature of protoplasm in the peculiar\nprocesses which take place in its constituent matter. Protoplasm is\nfor us a chemical matter, so pronounced, in fact, that the highest\nchemical actions that we know of are embodied in it.\" I must, from my\npoint of view, entirely reject Oscar Hertwig's conception of living\nmatter as a \"mixture\" of a number of chemical elements; because\nchemistry applies this phrase to various gases and powdery substances\nwhich are completely indifferent to each other--a property which we\ncertainly do not find in the constituents of protoplasm. When we speak\nof the living matter or protoplasm, the general phrase does not imply\nthat the substance may not have a distinctive composition in each\nparticular case. And when we find many biologists still conceiving\nprotoplasm as a mixture of various substances, the error is generally\ndue to a confusion of the chemical idea with the morphological, and to\na belief that certain structural features of the plasm are primary,\nwhereas they are only secondary, products of the vital process itself\nin the cell-body.\n\nThe older biologists who first introduced the name protoplasm and\nstudied it carefully recognized that this living matter belonged\nto the albuminous (or proteid) group. The many characteristics\nwhich distinguish these nitrogenous carbon-compounds from all\nother chemical compounds--their behavior towards acids and bases,\ntheir peculiar color-reaction towards certain salts, their\ndecomposition-products, etc.--are found in all the plasma-substances,\nand in all the other albuminoids. This is quite in agreement with\nthe results of quantitative analysis. However differently the\nvarious plasma-substances behave in detail, they always exhibit the\nsame general composition as the other albuminoids out of the five\n\"organogenetic elements\"--namely, in point of weight, fifty-one to\nfifty-four per cent. carbon, twenty-one to twenty-three per cent.\noxygen, fifteen to seventeen per cent. nitrogen, six to seven per\ncent. hydrogen, and one to two per cent. sulphur. However, there is\na good deal of variety and complication in the way in which the atoms\nof these five elements are combined in albumin and their molecules\nare grouped. Hence the question of the chemical nature of the\nplasma-substances compels us now to look for a moment at the larger\ngroup of albuminoids to which they belong.\n\nThe carbon-compounds which we comprise under the chemical title of the\nalbumins or proteids are the most remarkable, but also, unfortunately,\nthe least known, of all bodies. The attempt to examine them closely\nencounters extraordinary difficulties, greater than in any other group\nof chemical compounds. Everybody is familiar with the appearance of\nordinary albumin, from the transparent viscous albumin that surrounds\nthe yolk in the hen's egg, and which becomes a white, opaque, and solid\nmass when it is cooked. However, this special form of albumin, which we\ncan get so easily in any quantity from the eggs of birds and reptiles,\nis only one of the innumerable kinds of albumin, or species of protein,\nthat are to be found in the bodies of the various animals and plants.\nChemists have hitherto tried in vain to master the chemical structure\nof these obscure protein-compounds. They are only rarely to be found in\nchemically pure form as crystals. As a rule, they are in the colloid\nform, or uncrystallized jelly-like masses, which offer a much greater\nresistance than crystals to the passage through a porous medium by\ndiosmosis (see p. 39). However, although we have not yet succeeded in\npenetrating the molecular constitution of the albumins, the laborious\nresearch of chemists has yielded some general results which are of\ngreat importance for our purpose. We have, in the first place, a\ngeneral idea of their molecular constitution.\n\nMolecules are the smallest homogeneous parts into which a body can be\ndivided without altering its chemical character. Hence the molecules of\nevery chemical compound are made up of two or more atoms of different\nkinds. The greater the number of atoms in each compound, the higher\nis its molecular weight. The space between the molecules and their\ncomponent atoms is filled with imponderable and highly elastic ether.\nAs even the largest molecules occupy only a very tiny space, and\nremain far below the range of the most powerful microscope, all our\nideas of their composition depend on general physical theories and\nspecial chemical hypotheses. Nevertheless, stereochemistry, the modern\nscience of the molecular structure of chemical compounds, is not only\na perfectly legitimate section of natural philosophy, but it yields\nthe most important conclusions as to the mutual attractions of the\nelements and the invisible movements of the atoms in combining. It\nfurther enables us to calculate approximately the relative size of the\nmolecules and the number of atoms that are grouped together in them.\nHowever, the albuminoids present the greatest difficulty of all in this\ncalculation, and their structural features are still very obscure.\nNevertheless, science has reached certain general conclusions, which we\nmay formulate in the following propositions:\n\n1. The molecule of albumin is unusually large, and therefore its\nmolecular weight is very high (higher than in most or all other\ncompounds).\n\n2. The number of atoms composing it is very large (probably much more\nthan a thousand).\n\n3. The disposition of the atoms and groups of atoms in the albuminous\nmolecule is very complicated, and at the same time very unstable--that\nis to say, very changeable and easily altered.\n\nThese characters, which are ascribed to all albuminous bodies by\nmodern chemistry, hold good of all plasma-substances; and, in fact,\nare true in a higher degree of these, as the metabolism of the living\nmatter causes a constant displacement of the atoms. This is caused,\naccording to the view of Franz Hofmeister and others, by the formation\nof ferments or enzyma--in other words, by catalysators of a colloidal\nstructure. Verworn has, on physiological grounds, given the name of\nbiogens to these plasma-molecules.\n\nThe profound insight which comparative anatomy has given us into the\nsignificance and nature of organs, and comparative histology into\nthose of the cells, has naturally excited a desire to penetrate in the\nsame way the mystery of the elementary structure of the plasm, the\nchief active constituent of the cell. The improved methods of modern\ncytology, and the great progress which this science of the cell owes\nto the microtome and to microchemistry with its delicate coloring\nprocesses, etc., have prompted many observers of the last three decades\nto study the finest structural features of the elementary organism,\nand on this foundation build hypotheses as to the elementary structure\nof protoplasm. In my opinion, all these theoretical ideas, in so far\nas they would explain the finer structure of pure plasm, have a very\nserious defect; they relate to microscopic structures which do not\nbelong to the plasm as such (as a chemical body), but to the cell-body\n(or cytosoma), the chief active constituent of which is certainly the\nplasm. These microscopic structures are not the efficient causes of\nthe life-process, but products of it. They are phylogenetic outcomes\nof the manifold differentiations which the originally homogeneous and\nstructureless plasm has undergone in the course of many millions of\nyears. Hence I regard all these \"plasma-structures\" (the comb, threads,\ngranules, etc.), not as original and primary, but as acquired and\nsecondary. In so far as these structures affect the plasm as such, it\nmust take the name of metaplasm, or a differentiated plasm, modified\nby the life-process itself. The true protoplasm, or viscous and at\nfirst chemically homogeneous substance, cannot, in my opinion, have any\nanatomic structure. We shall see, when we come to consider the monera,\nthat very simple specimens of such organisms without organs still\nactually exist.\n\nBy far the greater part of the plasm that comes under investigation as\nactive living matter in organisms is metaplasm, or secondary plasm,\nthe originally homogeneous substance of which has acquired definite\nstructures by phyletic differentiations in the course of millions\nof years. To this modified plasm we must oppose the original simple\nprimary plasm, from the modification of which it has arisen. The name\n\"protoplasm,\" in the narrower sense, could very properly be retained\nfor this originally homogeneous form of structureless plasm; but, as\nthe term has now almost lost definite meaning and is used in many\ndifferent senses, it is, perhaps, better to call this pure homogeneous\nprimary plasm _archiplasm_. It is still found--firstly, in the body of\nmany (but not all) of the monera, part of the chromacea and bacteria,\nand the protam\u0153ba and protogenes; and, secondly, in the body of many\nvery young protists and tissue-cells. In the latter case, however,\nthere is already a chemical differentiation of the inner caryoplasm and\nouter cytoplasm. When we examine these young cells under a high power\nof the microscope, with the aid of the modern coloring methods, their\nprotoplasm seems to be perfectly homogeneous and structureless, or, at\nthe most, there are merely very fine granules regularly distributed in\nit which are believed to be products of metabolism. This is best seen\nin many of the rhizopods, especially the am\u0153b\u00e6, thalamophora, and\nmycetozoa. There are large am\u0153b\u00e6, which thrust out strongly mobile\nfeet from their unicellular body, broad, flaplike processes of the\nnaked cell body which constantly change their form, size, and place.\nIf they are killed and examined with the aid of the best methods of\ncoloring, it is quite impossible to detect any structure in them; and\nthis is also true of the pseudopodia of the mycetozoa and many other\nrhizopods. Moreover, the slow flowing movement of the fluid protoplasm\nshows clearly that there cannot be any composition out of fine fixed\nelements in the body. This is particularly clear in those am\u0153b\u00e6\nand mycetozoa in which a hyaline, firm, and non-granulated skin-layer\n(hyaloplasm) is more or less separated from a dark, softer, and\ngranulated marrow-layer (polioplasm); as both of them are viscous and\npass into each other without sharp limits, there cannot be any constant\nand fixed structural features in them.\n\nOrganic life--in its lowest and simplest form--is nothing but a form\nof metabolism, and therefore a purely chemical process. The whole\nvital activity of the chromacea, the simplest and oldest organisms\nthat we know, is confined to that process of metabolism which we\ncall plasmodomism or carbon-assimilation. The homogeneous and\nstructureless globules of protoplasm, which represent the whole frame\nof these primitive protophyta (chroococcus, aphanocapsa, etc.) in\nthe simplest conceivable way, expend their whole vital power in the\nprocess of self-maintenance. They maintain their individuality by a\nsimple metabolism; they grow by the addition of fresh plasm obtained\nby it, and they split up into two equal globules of plasm when the\ngrowth passes a certain limit--reproduction by clevage, maintenance\nof the species. Thus these chromacea have neither special organs, or\norganella, that we can distinguish in their simple plasma-bodies, nor\ndifferent functions in their life-process; it is wholly taken up with\nthe primitive work of their vegetal metabolism. We shall see later\non that this is a purely chemical process, something like catalysis\nin inorganic combinations; and for this neither special organs nor\nfine elementary structures in the plasm are needed. The \"end\" of their\nexistence, self-maintenance, is attained just as simply as in the\ncatalysis of any inorganic compound, or the formation of a crystal in\nits mother-water.\n\nIf we compare this very rudimentary life-process of the monera with\nthat of the highly differentiated protists (diatomes, desmidiacea,\nradiolaria, and infusoria), the biological distance between them seems\nto be immense; and it is, naturally, far greater when we extend the\ncomparison to the histona, the highly organized metaphyta and metazoa,\nin the bodies of which millions of cells co-operate in the work of the\nvarious tissues and organs.\n\nIn the great majority of cells--either the autonomous cells of the\nprotists or the tissue-cells of the histona--we can detect more or less\ndefinite and constant fine structures in the plasm. We must regard\nthese always as phyletic, secondary products of the life-process,\nand so call the differentiated plasm by the name of metaplasm. The\nvery different interpretations of the microscopic pictures which this\nmetaplasm affords have led to a good deal of controversy. In this the\ndesire to discover in these secondary plasma-structures the first\ncauses of vital action, or the real elementary organella of the cell,\nhas played a great part. The most important of the theories that\nhave been formulated are those of the frothy structure, the skeletal\nstructure, the fibrous structure, and the granulated structure of the\nplasm. All these theories of structure apply to plasm in general, but\nparticularly to its two chief forms, the caryoplasm of the nucleus and\nthe cytoplasm of the cell-body.\n\nAmong the many different attempts to discover a definite structure in\nliving matter, the theory of the frothy structure (also called the\nhoneycomb structure) has lately found the most favor. Otto B\u00fctschli,\nof Heidelberg, especially, has endeavored, on the basis of many years\nof careful study and experiment, to make it the foundation of his\nview of the plasm. It is undeniable that the living matter of many\ncells shows a delicate structure which may best be compared with\nfine soap-suds; innumerable globules are crowded close together in\na fluid, and flatten each other by their pressure into polyhedrical\nshapes. In 1892 B\u00fctschli artificially produced fine oil-suds by\nbeating up cane sugar or potash in olive oil, and then put a small\ndrop of the stuff in a drop of water under the microscope. The small\nparticles of sugar then exercised an attractive action by diffusion on\nthe particles of water; the latter penetrated into the oily matter,\nreleased the sugar, and formed tiny vesicles with it. As the vesicles\nof sugar do not mix with oil, they look like cavities isolated on\nall sides, and polyhedrically flattened by mutual pressure. The\nstriking resemblance of this artificially produced \"oil soap-suds\" to\nthe natural and microscopically visible structures of many kinds of\nplasm is strengthened from the fact that B\u00fctschli, Georg Quincke, and\nothers, have also observed similar flowing movements in both; and as\nthese apparently spontaneous movements can be explained physically and\nreduced to adhesion, imbibition, and other mechanical causes, there\nseemed a prospect of reducing the \"vital\" movements of the living\nand flowing plasm to purely physical forces. Quite recently Ludwig\nRhumbler, of G\u00f6ttingen, an authority on the rhizopods, has endeavored\nto give in this sense a _Physical analysis of the vital phenomena\nin the cell_. To-day the froth theory is much the most popular of\nthe many attempts to detect a fine plasm-structure as the essential\nanatomic foundation of an explanation of the physiological functions.\nIt must be noted, however, that frequently very different phenomena\nare confused under this name, especially the coarser froth-formation\nby taking up water in the living matter and the invisible hypothetical\nmolecular structure. Both these must be distinguished from the finer\nplasma-structure which is visible under a powerful microscope; but the\nlimit between them is difficult to determine.\n\nA second view of the finer structure of the plasm, which had been\ngreatly esteemed before the acceptance of the froth theory, was\nformulated in 1875 by Carl Frommann and Carl Heitzmann, and supported\nby Leydig, Schwitz, and others. It puts another interpretation on the\nnet-like appearance of the microscopic plasma-structure. It assumes\nthat the plasma consists of a skeleton of fine threads or fibrils\ncombined in the form of a net, and that these spread and cross in the\nbody of the cell which is filled with fluid. It is also compared to a\nsponge, and is said to have a spongy structure. We can artificially\nproduce such a skeletal structure by, for instance, causing coagulation\nin a thick solution of glue or albumin by adding alcohol or chromic\nacid. It is unquestionable that there are these \"plasma-skeletons\" both\nin the nucleus and the body of the cell; but they are generally (if not\nalways) secondary products of organization in the elementary organism\n(or cell-organs), not primitive structures of its plasm. Moreover, an\noptical transverse action of a froth-structure or honeycomb, examined\nas a flat surface in the microscope, shows the same configuration as\na fine skeleton. We can hardly see any difference between the two. We\ncannot accept the skeletal formation as a fundamental structure of the\nplasm.\n\nAs we notice very fine threads in the plasm of many cells, both in\nthe caryoplasm of the nucleus and the cytoplasm of the cell body,\nthe cytologist Flemming, of Kiel (1882), believed it was possible to\ndiscover them in the plasm of all cells, and based on this his filar\ntheory of plasm. He says that we must distinguish two chemically\ndifferent kinds of plasm in living matter--the filar (threadlike) and\nthe inter-filar matter. The fine threads of the former are of different\nlengths, and sometimes run separately, at other times are bound in a\nsort of net-work (_mitoma_ and _paramitoma_). In certain conditions of\ncell-life, especially in indirect cell-division, these filar formations\nplay a great part; and also in the functions of highly differentiated\ncells, such as the ganglionic cells. But in many cases these plasma\nthreads may be merely parts of a skeletal or frothy structure\n(honeycomb walls in section). In any case, we cannot regard the thread\nformation as a general elementary structure of plasm; in my opinion, it\nis always a secondary phyletic product of living matter, and never a\nprimary feature of it.\n\nTotally different from the three preceding theories of the finer\nstructure of the plasm is the granular theory of Altmann (1890). He\nsupposes that all living matter is originally made up of tiny round\ngranules, and that these independently living _bioblasts_ are the real\n\"elementary organisms,\" the microscopic ultimate individuals; hence\nthe cells which are formed by the combination of these granules must\nbe looked on as individuals of the second order. Between the granules\nof the granulated substance (the real active living matter) there\nis always an inter-granular substance; the granules are regularly\ndistributed and arranged in these. The granules themselves, or the\nbioblasts, are homogeneous, sometimes globular, and sometimes oval,\nor of other shapes. However, the distinction between these substances\nis quite arbitrary, and neither chemically nor morphologically well\ndefined. Under the head of granules Altmann throws together the most\ndifferent contents of the cell--fat granules, pigment granules,\nsecretory granules, and other products of metabolism. Hence his\ngranular theory is now generally rejected. However, there was a\nsound idea at the bottom of it--namely, the idea of explaining the\nvital properties and functions of living matter by small separate\nconstituents which make up the plasm, and move in a viscous medium.\nBut these real elementary parts are not microscopically visible;\nthey belong to the molecular world, which lies far below the limit\nof microscopic power. In my opinion, Altmann's visible granules,\nlike Flemming's threads and Frommann's skeleton and B\u00fctschli's\nhoneycomb, are not primary structures, but secondary products of plasma\ndifferentiation.\n\nAs the special properties and activities of any natural body depend on\nits chemical constitution, and this is, in the long-run, determined\nby the composition of its molecules, it is a matter of the greatest\ninterest in biology to form as clear and distinct an idea as possible\nof the nature and properties of the molecules of plasm. Unfortunately,\nit is only possible to do this approximately, and to a slight extent.\nAs the hypotheses of modern structural chemistry on the molecular\nformation of complicated organic compounds are often very unsafe,\nthis is bound to be the case in the highest degree as regards the\nalbuminoids and, the most important of all, the living matter or plasm.\nWe have as yet no knowledge of the fundamental features of its very\nvariable chemical structure. The one thing that bio-chemists have told\nus about it is that the molecule of plasm is very large, and made up of\na great number of atoms (over a thousand); and that these are combined\nin smaller or larger groups, and are in a state of very unstable\nequilibrium, so that the life process itself causes constant changes in\nthem.\n\nSince the great problem of heredity was forced by Darwin in 1859\ninto the foreground of general biology, many different hypotheses\nand theories of it have been framed. All these have in the end to\ntrace it to molecular features in the plasm of the germ-cells;\nbecause it is this germ-plasm of the maternal ovum and the paternal\nsperm-cell that conveys the characteristics of the parents to the\nchild. Hence the great progress that has been made recently in the\nstudy of conception and heredity, by means of a number of remarkable\nobservations and experiments, has been of service to our ideas on\nthe molecular structure of the plasm. I have dealt with the chief of\nthese theories in the ninth chapter of my _History of Creation_, and\nmust refer the reader thereto. In chronological order we have: (1)\nthe pangenesis theory of Darwin (1868), (2) the perigenesis theory of\nHaeckel (1875), (3) the idioplasm theory of N\u00e4geli (1884), (4) the\ngerm-plasm theory of Weismann (1885), and (5) the mutation-theory of De\nBries (1889). None of these attempts, and none of the later theories\nof heredity, has given us a satisfactory and generally admitted idea\nof the plasma-structure. We are not even clear as to whether in the\nlast resort life is to be traced to the several molecules, or to groups\nof molecules, in the plasm. With an eye to this latter difference, we\nmay distinguish the plastidule and micellar theories as two different\ngroups of relevant hypotheses.\n\nIn my essay on \"The Perigenesis of the Plastidules\" (1875) I formulated\nthe hypothesis that in the last instance the plastidules are the\nvehicles of heredity--that is to say, plasma-molecules which have the\nproperty of _memory_. In this I found support in the ingenious theory\nof the distinguished physiologist, Ewald Hering, who had declared in\n1870 that \"memory is a general property of organic matter.\" I do not\nsee still how heredity can be explained without this assumption! The\nvery word \"reproduction,\" which is common to both processes, expresses\nthe common character of psychic memory (as a function of the brain). By\nplastidules I understand simple molecules; the homogeneous nature of\nthe plasm in the monera (both chromacea and bacteria and rhizomonera)\nand the primitive simplicity of their life-functions do not dispose\nus to think that special groups of molecules are to be distinguished\nin these cases. Max Verworn has recently (1903) formulated his\nbiogen-hypothesis in the same sense, as a \"critical-experimental study\nof the processes in the living matter.\" He also takes the active\nplasma-molecules, which he calls biogens, as the ultimate individual\nfactors of the life-process, and is convinced that in the simplest\ncases the plasm consists of homogeneous biogen-molecules.\n\nThe hypothesis of N\u00e4geli (1884) and Weismann (1885) is totally\ndifferent from the hypothesis of the plastidules and biogens as\nsimple molecules of the plasm. According to this, the ultimate \"vital\nunities\" or individual vehicles of the life-process are not homogeneous\nplasma-molecules, but groups of molecules, made up of a number of\ndifferent molecules. N\u00e4geli calls them _micella_, and assigns them a\ncrystalline structure. He supposes that these micella are combined\nchainwise into micellar ropes, and that the variety of the many forms\nand functions of plasm is due to the different configuration and\narrangement of these. Weismann says: \"Life can only arise by a definite\ncombination of different kinds of molecules, and all living matter\nmust be made up of these groups of molecules. A single molecule cannot\nlive, can neither assimilate nor grow nor reproduce.\" I do not see\nthe justice of this observation. All the chemical and physiological\nproperties which Weismann afterwards attributes to his hypothetical\n_biophora_ may be ascribed to a single molecule just as well as to\na group of molecules. In the simplest forms of the monera (both the\nchromacea and the bacteria) the nature of their rudimentary life\ncan be explained on the one supposition just as well as the other.\nNaturally, this does not exclude a very complicated chemical structure\nin the large plastidule or biogen as a single molecule. Verworn's\nbiogen-hypothesis seems to me quite satisfactory when it represents the\nprimitive molecule of living matter as really the ultimate factor of\nlife.\n\nThe chief process in the evolutionary history of the plasm is its\nseparation into the inner nuclear matter (caryoplasm) and the outer\ncellular matter (cytoplasm). When both kinds of plasm arose by\ndifferentiation from the originally simple plasm of the monera, there\nalso took place the morphological separation of the nucleus (caryon)\nand cell-body (cytosoma or celleus). As these two chief forms of living\nmatter are chemically different but nearly related, and as they may\nin certain circumstances (for instance, during indirect cell-division\nand the partial caryolysis connected therewith) enter into the closest\nmutual relations, we must suppose that the original severance of the\ntwo substances took place gradually and during a long period of time.\nIt was not by a sudden bound or transformation, but by a gradual\nand progressive formation of the chemical antithesis of caryoplasm\nand cytoplasm, that the real nucleated cell (cytos) arose from the\nunnucleated cytode (or primitive cell). Both may correctly be comprised\nunder the general head of _plastids_ (or formative principles), as\n\"ultimate individualities.\"\n\nI regard as the chief cause of this important differentiation of the\nplasm the accumulation of hereditary matter--that is to say, of the\ninternal characteristics of the plastids acquired by ancestors and\ntransmitted to their descendants--within the plastids while their\nouter portion continued to maintain the intercourse with the outer\nworld. In this way the inner nucleus became the organ of heredity\nand reproduction, and the outer cell-body the organ of adaptation\nand nutrition. I put forward this hypothesis in 1866 in my _General\nMorphology:_ \"The two functions of heredity and adaptation seem to\nbe not yet distributed between differentiated substances in the\nunnucleated cytodes, but to inhere in the whole of the homogeneous mass\nof the plasm; while in the nucleated cell they are divided between\nthe two active constituents of the cell, the inner nucleus taking\nover the transmission of hereditary characters and the outer plasm\nundertaking adaptation, or the accommodation to the features of the\nenvironment.\" This hypothesis was afterwards (1873) confirmed by the\ndiscoveries of Strasburger, the brothers Hertwig, and others, with\nregard to cell-cleavage and fertilization; it is particularly supported\nby the phenomena of _caryokinesis_(the movement of the nucleus) in\nsexual generation. Hence we can understand how it is that in the monera\n(chromacea and bacteria), which propagate by simple cleavage, there is\nno sexual generation and no nucleus.\n\nThe great significance of the nucleus in the life of the cell, as\ncentral organ of heredity, and also probably as \"the soul of the\ncell,\" depends chiefly on the chemical properties of its albuminous\nmatter, the caryoplasm. This one indispensable nuclear element is\nchemically akin to the cytoplasm of the cell-body, but differs from it\nin certain respects. The caryoplasm has a greater affinity for many\ncoloring matters (carmine, h\u00e6matoxylin, etc.) than the cytoplasm; and\nthe former coagulates more quickly and firmly than the latter through\nacids (such as acetic and chromic acid). Hence we need only add a drop\nof diluted (two per cent.) acetic acid to cells that seem homogeneous\nto make perfectly clear the separation between the inner nucleus and\nouter body. As a rule, the firmer nucleus then stands out sharply as\na globular or oval particle of plasm; occasionally it has other forms\n(cylindrical, conical, spiral, or branched). The caryoplasm seems\nto be originally quite homogeneous and structureless, as we find\nin many of the protists and many young cells of histona (especially\nyoung embryos). But in the great majority of cells the caryoplasm is\ndivided into two or more different substances, the chief of them being\nchromatin and achromin.\n\nThe most common division of the caryoplasm in the cells of the animal\nand plant body, and the one of chief significance for their vital\nactivity, is that into two chemically different substances, which\nare usually called chromatin (or nuclein) and achromin (or linin).\nChromatin has a greater affinity for coloring (_chromos_) matter\n(carmine, h\u00e6matoxylin, etc.), and so this \"colorable nuclear matter\"\nis particularly regarded as the vehicle of heredity. The achromin (or\nachromatin, or linin) is either not at all or less easily colorable,\nand is akin to the cytoplasm; in direct cell-division it enters into\nclose relations with the latter. Achromin is usually found in the\nform of slender threads, and hence called \"nuclear thread-matter\"\n(linin). Chromatin is generally found in roundish or rod-shaped\ngranules (chromosomata), which exhibit very characteristic changes of\nform (loop formation, etc.) in indirect cell-division. The chemical,\nphysiological, and morphological difference between chromatin and\nachromin must not be regarded as an original property of cell nuclei\n(as is wrongly stated sometimes), but is the outcome of a very early\nphylogenetic differentiation in the originally homogeneous caryoplasm;\nand this holds also of two other parts of the nucleus--the nucleolus\nand centrosoma.\n\nIn a good many cells, but by no means universally, we find two other\nconstituents of the nucleus, which owe their rise to a further\ndifferentiation of the caryoplasm. The nucleolus is a small globular or\noval particle, which may be found singly or in numbers in the nucleus,\nand behaves somewhat differently towards coloring matter than the\nclosely related chromatin. It has a special affinity for acid aniline\ncolors, gosin, etc. Its substance has, therefore, been distinguished\nas _plastin_ or _paranuclein_. The nucleolus is especially found in\nthe tissue-cells of the higher animals and plants as an independent\nconstituent; it is wanting in many of the unicellular protists. The\nsame may be said of the centrosoma, or \"central body\" of the cell.\nThis is an extremely small granule, on the very limit of visibility,\nthe chemical composition of which is not known very well. We should\nhave paid no attention to this constituent of the cell (distinguished\nin 1876) if it did not play an important, and perhaps leading, part\nin indirect cell-division. As the \"polar body in the division of\nthe nucleus,\" the centrosoma exercises a peculiar attraction on the\ngranules distributed in the cytoplasm, which arrange themselves\nradially about this centre. The centrosomata grow independently and\nincrease by cleavage, like the chromoplasts (chlorophyll particles,\netc.). When they have split up, each of the daughter-microsomata acts\nin turn as a centre of attraction on its half of the cell. However, the\ngreat importance which modern cytologists have ascribed to it on this\naccount is discounted by two circumstances. In the first place, we have\nnot succeeded, in spite of all efforts, in discovering a centrosoma in\nthe cells of the higher plants and many of the protists; and, in the\nsecond place, a number of recent chemical experiments have succeeded in\nproducing centrosomata artificially (for instance, by the addition of\nmagnesium chloride) in the cytoplasm. Hence many cytologists regard the\ncentrosoma as a secondary product of differentiation in the cell-body,\nnot the nucleus.\n\nTwo other parts of the nucleus that we find very often, but by no means\nuniversally, in the cells of the animal and plant body are the nuclear\nmembrane (caryotheca) and the nuclear sap (caryolymph). A large number\nof cells--but not all--have the appearance of vesicles, having a thin\nskin enclosing a liquid content, the nuclear sap. The achromin then\nusually forms a frame-work of threads, with chromatin granules in its\nmeshes or knots, within this round vesicle. This very thin nuclear\nmembrane (often only visible as its contour) or caryotheca may be\nregarded as the result of surface-strain (at the planes of contact of\ncaryoplasm and cytoplasm). The watery and usually clear and transparent\nnuclear sap (caryolymph) is formed by imbibition of watery fluid (like\nthe frothy structure of the plasm in general). The separation of the\nnuclear membrane and nuclear sap is not a primary property of the\nnucleus, but is due to a secondary differentiation in the originally\nhomogeneous caryoplasm.\n\nLike the caryoplasm of the nucleus, the cytoplasm of the cell-body is\noriginally a chemical modification of the simple and once homogeneous\nplasm (the archiplasm). This is clearly shown by the comparative\nbiology of the protists, their unicellular organism presenting a much\ngreater variety of stages of cell-organization than the subordinate\ntissue-cells in the bodies of the multicellular histona. However, in\nthe great majority of cells the cytoplasm is separated into several,\nand frequently very numerous, parts, which have received diverse forms\nand functions in the division of labor. We then see very conspicuously\nthe regularity of cell-organization, which is altogether wanting in\nthe simple homogeneous plasma granules of the monera. As this great\ndifferentiation of the advanced elementary organism is incorrectly\ngeneralized by some recent cytologists and described as a universal\nfeature of cells, it is necessary to insist explicitly that it is a\nsecondary phylogenetic development, and is altogether wanting in the\nprimitive organisms. The complexity of the physiological division\nof labor and the accompanying morphological separation of parts is\nextremely great in the cytoplasm. When we wish to arrange them in a\nfew large groups from a general point of view, we may distinguish the\nactive plasma-formations from the passive plasma-products; the former\nare due to a chemical metamorphosis of the living plasm, the latter\nlifeless excretions from it.\n\nUnder the head of plasm-formations, or products of differentiation\nin the cytoplasm, we comprise all formations that are due to partial\nmetamorphosis of the living cell-body--not lifeless excretions from\nit, but living parts of its substance, undertaking special functions,\nand therefore chemically and morphologically differentiated from the\nprimary cytoplasm. One of the commonest differentiations of this\nkind is the separation of the firm hyaline skin-layer (hyaloplasm)\nfrom the softer granular marrow-layer (polioplasm); though the two\noften pass into each other without clear limits. In most plant-cells\nspecial granules of plasm, mostly globular or roundish, are developed,\ncalled _trophoplasts_, and these undertake the work of metabolism.\nTo this class belong the amyloplasts, which produce starch (amylum),\nthe chloroplasts or chlorophyll-granules which form the green\nmatter (chlorophyll) in the leaf, and the chromoplasts which form\ncolor-crystals of various sorts. In the cells of the higher animals the\nmyoplasts form the special contractile tissue of the muscles, and the\nneuroplasts the psychic tissue of the nerve-matter. On the other hand,\nthe distinction between the body-plasm (somoplasma) and the germ-plasm\n(germoplasma), which serves as the base of Weismann's untenable theory\nof the germ-plasm (_cf._ chapter xvi.), is purely hypothetical and\nwithout direct observation to support it.\n\nThe infinite variety of parts of the cell which arise as excretions\nof the living active cytoplasm, and so must be regarded as lifeless\nplasma-products, may be divided into two chief groups--internal and\nexternal. The former are stored within the living cytoplasm, the\nlatter thrust out from it.\n\nInternal plasma-products of common occurrence are the microsomata,\nvery small and opaque particles which are generally regarded as\nproducts of metabolism. They consist sometimes of fat, sometimes of\nderivatives of albumin, sometimes of other substances of which we do\nnot know the chemical composition. The same may be said of the large\nand variously-colored pigment-granules, which are very common and\ndetermine the color of tissues. Also very common in the cytoplasm are\nlarge accumulations of fat in the shape of oil-globules, fat-crystals,\netc., besides other crystals of a very different sort, partly organic\ncrystals (for instance, albuminous crystals in the aleuron-granules\nof plants), partly inorganic crystals (for instance, of oxalic-acid\nsalts in many plant-cells, of calcareous salts in many animal-cells).\nThe watery cell-sap (cytolymph) plays an important part in many of\nthe larger cells. It is formed by the accumulation of fluid in the\ncytoplasm, and is found in its frothy structure. The large empty spaces\nwhich it forms are called vacuoles, with very regularly disposed\nalveoles. When the cell-sap gathers in great abundance within the cell,\nwe get the large vesicular cells which are found in the tissues of the\nhigher plants, the cartilages, etc.\n\nAs external excretions of the living cytoplasm that have acquired\nsome importance, especially as protective organs, in the majority of\ncells, we have first of all the cell-membranes, the firm capsules or\nprotective skins which enclose the soft cell-body, like a snail in\nits house. In the first period of the cell-theory (1838-1859) such an\nintegument was ascribed to all cells, and often regarded as their chief\nconstituent; but it was discovered afterwards that this protective\nskin is altogether wanting in many (especially animal) cells, and that\nit is not found in many when they are young, but grows subsequently.\nWe now distinguish between naked cells (gymnocytes) and covered cells\n(thecocytes). As examples of naked cells we have the am\u0153b\u00e6, and many\nof the infusoria, the spores of alg\u00e6, the spermatozoa, and many animal\ntissue-cells.\n\nThe cell-covering (cytotheca) varies very much in size, shape,\ncomposition, and chemical character, especially in the rhizopods\namong the unicellular protists. The flint shells of the radiolaria\nand diatomes, the chalky cells of the thalamophora and calcocytea,\nthe cellulose shells of the desmidiacea and syphonea, show the\nextraordinary plasticity of the constructive cytoplasm (_cf._ chapter\nviii.). Among the histona the tissue-plants are remarkable for the\ninfinite variety of shape and differentiation of their cellulose\ncapsules. The familiar properties of wood, cork, bast, the hard shells\nof fruit, etc., are due to the manifold chemical modification and\nmorphological differentiation which the cellulose membrane undergoes in\nthe tissues of plants. This is less frequently seen in the tissues of\nanimals; but, on the other hand, the intercellular and the cuticular\nmatter play a greater part in these.\n\nThe intercellular matter, an important external plasma-product, is\nformed by the social cells in the tissues of the histona thrusting\nout in common firm protective membranes. These protective structures\nare very common among communities of protists, in the form of masses\nof jelly, in which a number of cells of the same kind are united;\nsuch are the zoogl\u0153a of many of the bacteria and chromacea, the\ncommon jelly-like envelope of the volvocina and many diatomes, and the\nglobular cell-communities of the polycyttaria (or social radiolaria).\nThe chief part is played by intercellular matter in the body of the\nhigher animals, in the form of mesenchyma-tissue; the connecting\ntissue, cartilages, and bones owe their peculiar property to the\namount and quality of the intercellular matter that is deposited\nbetween the social cells.\n\nWhen the socially joined epidermic cells at the surface of the\ntissue-body thrust forth in common a protective covering, we get the\ncuticles, which are often thick and solid armor-plates. In many of\nthe metaphyta wax and flinty matter are deposited in the cellulose\ncuticles. The strongest formation is found in the invertebrate animals,\nwhere the cuticle often determines the whole shape and articulation,\nas in the calcareous shells of mollusks (mussel-shells, snail-shells,\ncockle-shells, etc.); and especially the coats of the articulata (the\ncrab's coat of mail, and the skins of spiders and insects).\n\n\n\n\nVII\n\nUNITIES OF LIFE\n\n Units of life--Simple and complex organisms--Morphological and\n physiological individuals--Morphonta and bionta--Stages of\n individuality: cell, person, stem--Actual and virtual bionta--Partial\n and genealogical bionta--Metaphysical individuals--Cells (elementary\n organisms)--Cell membranes--Unnucleated cells--Plastids (cytodes\n and cells)--Primitive cells and nucleated cells--Organella (cell\n organs)--Cell communities (c\u0153nobia)--Tissues of histona--Systems\n of organs--Organic apparatus--Histonal individuals (sprouts and\n persons)--Articulation of the histona (metamerism)--Stems of the\n histona--Animal states.\n\n\nThe dissection of the body of the higher animal and plant into\nits various organs soon prompted comparative anatomists to draw a\ndistinction between simple and complex organisms. Then, when the\ncell-theory developed in the course of the last half-century, the\ncommon anatomic groundwork of all living forms was recognized in\nthe cell; and the conception of the cell as the elementary organism\nled to the further belief that our own frame, like that of all the\nhigher animals and plants, is a cell-state, composed of millions of\nmicroscopic citizens, the individual cells, which work more or less\nindependently therein, and co-operate for the common purposes of the\nentire community. This fundamental principle of the modern cell-theory\nwas applied with great success by Rudolph Virchow to the diseased\norganism, and led to most important reforms in medicine. The cells are,\nin his view, independent \"life-unities or individual life-centres,\"\nand the unified life of the whole man is the combined result of the\nwork of his component cells. In this way the cells are the real\nlife-unities of the organism. Their individual independence is at once\nseen in the permanently unicellular protists, of which several thousand\nspecies are already known to us.\n\nOn the other hand, we find among the lower animals and the higher\nplants a composition of homogeneous parts, which represents a higher\nstage of life-unity. The tree is an individual, but it is made up of\na number of branches or individual sprouts, each of which consists\nin like manner of an axial stem with leaves attached. If we detach\nsuch a branch and plant it in the ground, it takes root and grows\ninto an independent plant. So the coral-stem is made up of a number\nof individual animals or persons, each of which has its own stomach\nand mouth with a crown of tentacles. Each several coral-individual is\nequivalent to a single living polyp (actinia). Thus the stem (_cormus_)\nis a higher unity, both in the animal and the plant world. Even the\nherds of gregarious animals, the swarms of bees and ants, and the\ncommunities of human beings, are similar unities; with the difference\nthat the individual persons or citizens are not physically connected,\nbut held together by common interests. We can, therefore, distinguish\nthree stages of organic individuality, one building upon the other--the\ncell, the person (or sprout), and the stem or state (cormus). Each\nhigher unity represents an intimate union of lower individuals.\nMorphologically, in relation to their anatomic structure, the latter\nare independent; but physiologically, in respect of the life-unity of\nthe whole, they are subordinated to the former.\n\nThis relation is quite clear in the familiar examples I have quoted.\nBut there are other organisms in which this is not so, and where the\nquestion of the real individuality is very difficult to answer.\nThus, fifty years ago, we came to recognize floating animal-stems in\nthe remarkable siphonophora, or social medus\u00e6, which had hitherto\nbeen regarded as individual animals, or medus\u00e6 with a multiplicity\nof organs; further study proved that each of these apparent organs\nis really a modified medusa, and the whole united structure a stem.\nThis example throws a good deal of light on the important question of\nassociation and division of labor. The whole floating siphonophoron\nis, physiologically considered (in respect of its vital activity), a\nharmoniously organized animal with a number of different organs; but\nfrom the morphological point of view (in respect of form and structure)\neach dependent organ is really an independent medusa.\n\nIt is clear, from these few illustrations, that the question of\norganic individuality is by no means so simple as it seems at first\nsight, and that it receives different answers according as we look\nat the form and structure (morphologically) or the vital and psychic\nactivity (physiologically). We must, therefore, distinguish at once\nbetween morphological (_morphonta_) and physiological (_bionta_)\nindividuals. The tree and the siphonophoron are bionta, or individuals\nof the highest order, made up of a number of similar branches or\npersons, the social morphonta. But, when we further dissect the latter\nanatomically into their various organs, and these again into their\nmicroscopic elements, the cells, each branch or person seems to be a\nbion, and their cells to be morphonta. Each multicellular organism is,\nhowever, developed in the beginning from a single cell, the stem-cell\n(cytula) or fertilized ovum; this is at once a morphon and a bion, a\nsimple individual both morphologically and physiologically. The whole\nprocess of its development into a multicellular organism consists in a\nrepeated cleavage of the stem-cell, the resultant cells being joined\nin a higher unity, and assuming different forms in consequence of the\ndivision of work.\n\nThe complicated modern state, with its remarkable achievements, may be\nregarded as the highest stage of individual perfection which is known\nto us in organic nature. But we can only understand the structure of\nthis extremely complex \"organism of the highest order,\" and its social\nforms and functions, when we have a sociological knowledge of the\nvarious classes that compose it, and the laws of their association and\ndivision of labor; and when we have made an anthropological study of\nthe nature of the persons who have united, under the same laws, for the\nformation of a community and are distributed in its various classes.\nThe familiar arrangement of these classes, and the settling of the rank\nin the mass and the governing body, show us how this complex social\norganism is built up step by step.\n\nBut we have to look in the same way on the cell-state, which is made\nup from the separate individualities in human society or in the\nkingdom of the tissue-animals, or the branches in the kingdom of the\ntissue-plants. Their complex organism, composed of various organs and\ntissues, can only be understood when we are acquainted with their\nconstituent elements, the cells, and the laws according to which these\nelementary organisms unite to form cell-communities and tissues, and\nare in turn modified in the divers organs in the division of labor. We\nmust, therefore, first establish the scale of the morphonta, and the\nlaws of their association and ergonomy, according to which the several\nstages or conditions of morphological individuality build on each\nother. Three such stages may be at once distinguished: (1) the cell\n(or, more correctly, the plastid), (2) the person (animal) or branch\n(vegetal), and (3) the stem or cormus. But we shall find that there\nare further subordinate stages under each of these three. It is only\nin the case of the protists that the morphological unity is bound up\nwith the physiological. In the case of the histona, the multicellular,\ntissue-forming organisms, this is only so at the beginning of\nindividual existence (at the stage of the stem-cell). As soon as the\nmulticellular body arises from this cytula by repeated segmentation, it\nis raised to the stage of a higher individuality, the cell-state.\n\nOur own human frame is, in its mature condition, like that of all the\nhigher animals, a very complete cell-state, but a single cell at the\nbeginning of its existence. We speak of the life-unity of the former\nas an actual bion, and that of the latter as a virtual bion; in other\nwords, the physiological individual or the life-unity has in the first\ncase reached the highest stage of individual development that pertains\nto its species, while in the second case it remains at the lowest\nstage of virtual formation, and has only the capacity of rising to\nthe higher stage. In the higher plants and animals only one cell of\nthe organism, or the two combined sexual cells (ovum and spermium),\nare the potential bion which may develop into an actual one. There\nare, however, exceptions. In the fresh-water polyp (hydra) and cognate\ncnidaria each piece of the body-wall, in the bath-sponge (euspongia)\nand similar sponges each piece of tissue, and in many plants (for\ninstance, marchantia among the crytogams and bryophyllum among the\nphanerogams) each portion of a branch or leaf, has the power to develop\ninto a mature organism, and is, therefore, a virtual bion.\n\nFrom these virtual bionta (parts of the body that may grow into whole\norganisms) we must distinguish the partial bionta which have not this\nproperty. These are separated parts of the body that live for a time\nafter being cut off from the whole organism, but then die off. Thus,\nfor instance, the heart of a tortoise beats for a long time after being\ncut out. A flower that has been plucked may, if put in water, keep\nfresh and alive for many days. In some highly organized cephalopods one\nof the eight arms of the male develops into an independent body, swims\nabout, and accomplishes the fertilization of the female (_hectocotylus_\namong the _argonauta_, _philonexis_, etc.). It was at first thought\nto be an independent animal parasite. The same thing happens with\nthe remarkable foldlike dorsal appendages of a large naked snail\n(_thetys_), which get detached and creep about. The body of many of\nthe lower animals may be cut in pieces and yet may live for weeks. The\nlife-properties of these partial bionta are important in view of the\ngeneral question of the nature of life and its apparent unity in most\nof the higher organisms. As a fact, even here the cells and organs lead\ntheir separate individual life, though they are subordinate to and\ndependent on the whole.\n\nIt has been attempted to answer this question of organic individuality\nin the sense of counting all organisms individuals which develop from\na single fertilized ovum. Thus, the Italian botanist Gallesio, in\n1816, regarded all plants that arise by asexual generation (budding\nor segmentation)--sprouts, branches, slips, bulbs, etc.--as merely\nportions of a single individual that came from an egg (the seed).\nSo also Huxley, in 1855, considered the sum of all the animals that\nhave been produced by asexual propagation, but from a single sexually\ngenerated animal, to be parts of one individual. In practice, however,\nthis principle is useless. We should have to say that the millions\nof plant-lice which arise parthenogenetically from unfertilized\ngerm-cells, but are originally descended from one impregnated ovum,\nare one single individual; so also all the weeping-willows in Europe,\nbecause they all came from shoots of one single sexually-produced tree.\n\nMany attempts have been made in the course of the nineteenth century\nto give a generally satisfactory answer to this difficult question of\nthe content and connotation of the idea of the organic individual.\nNone of these has found general favor. I have compared and criticised\nthem in the third book of my _General Morphology_. I there paid\nspecial attention to the views of Goethe, Alexander Braun, and N\u00e4geli\namong the botanists, and Johannes M\u00fcller, Leuckart, and Victor Carus\namong the zoologists. When we consider the striking divergence of the\nviews of such distinguished scientists and thinkers on so important a\nbiological question, we can understand that opinions are still very\ndivided to-day. Hence we must not be too hard on the metaphysical\nphilosophers when--in complete ignorance of the real facts--they rear\nthe most extraordinary theories in their airy speculations on \"the\nprinciple of individuation\". Compare, for instance, the opinions of the\nschool-men and those of recent thinkers such as Arthur Schopenhauer and\nEdward Hartmann. As a rule, the psychological side of the problem--the\nquestion of the individual soul--is very prominent, without much\nattention being paid to its material substratum--the anatomic basis of\nthe organism. Many metaphysicians, who, in their one-sided anthropism,\nmake man here also the measure of all things, would assign personal\nconsciousness as the basis of the idea of individuality. It is obvious\nthat this is not a practicable test even for the higher animals, to\nsay nothing of the lower animals and plants. In these we have a far\ngreater variety of individuality on the one hand, and a far greater\nsimplicity of construction on the other. I have tried to show, in my\nessay on \"The Individuality of the Animal Body\" (1878), the easiest way\nto answer these complicated tectological questions, and to support it\nby the science of structure. It suffices to distinguish the three chief\nstages I have mentioned, and to explain clearly their physiological\nsignificance on the one hand and morphological on the other. We will\ntherefore consider the cell first, then the person (or sprout), and,\nfinally, the stock (or cormus).\n\nEver since the middle of the nineteenth century the cell theory has\nbeen generally and rightly considered one of the most important\ntheories in biology. Every anatomical, histological, physiological, and\nontogenetic work must build on the idea of the cell as the elementary\norganism. Nevertheless, we are still very far from having a general\nand clear agreement as to this universal and fundamental idea. On\nthe contrary, the ablest biologists still differ considerably as to\nthe nature of the cell or the elementary individual, its relation to\nthe whole of the multicellular organism, and so on. This divergence\nof views is partly due to the intricacy of the phenomena we find in\nthe life of the cell, and partly to the many and extensive changes\nthat have been made in the meaning of the term in the course of its\nemployment. Let us first cast a glance at the various stages of its\nhistory.\n\nWhen in the last third of the seventeenth century a number of\nscientists, especially Malpighi in Italy and Crew in England, used the\nmicroscope for the first time in the anatomic study of plant structure,\nthey noticed a certain build of the tissue that closely resembled the\nhoneycomb. The closely packed wax cells, filled with honey, of the\nhive, which show a hexagonal appearance in section, are like the wood\ncells that contain the sap in the plant. It was the great merit of\nSchleiden, the real founder of the cell theory, to prove that _all_\nthe different tissues of plants are originally composed of such cells\n(1838). Theodor Schwann soon afterwards proved the same for the animal\ntissues; in 1839 he extended the theory to the whole organic world.\nBoth these scientists regarded the cell as essentially a vesicle, the\nfirm membrane of which enclosed a fluid content, and a solid smaller\nbody inside this, which R. Brown had recognized as the nucleus in 1833.\nThey compared the cell, as a microscopic individual, to an organic\ncrystal, and thought it arose by a sort of crystallization in an\norganic medium (cytoblastema); in this the central nucleus would serve\nas starting-point like the nucleus of the crystal.\n\nIn the first twenty years (1839-59) of the cell theory it was a fixed\nprinciple that there were three essential parts of the cell. Firstly,\nthere was the strong outer membrane, which was not only regarded as a\nprotective covering, but also credited with a great deal of importance\nas an element in the building of the organism. In the second place,\nthere was the fluid or semi-fluid content (the sap); and, thirdly,\nthe firm nucleus enclosed in the sap. In order to give a clearer idea\nof the relative thickness and disposition of these parts, the cell\nwas compared to a cherry or a plum. The soft flesh of this fruit\n(corresponding to the cell sap) can, with difficulty, be separated from\nthe external firm skin or from the hard stone within. A great step in\nadvance was made in 1860, when Max Schultze showed that the external\nmembrane was an unessential and secondarily formed part of the cell.\nIt is, as a fact, altogether wanting in many, especially young, cells\nof the animal body. They are naked cells without any membrane. The\ndistinguished anatomist also proved that the so-called \"cell sap\"--the\nreal body of the cell--is not a simple fluid, but a viscous, albuminous\nsubstance, the independent movements of which had long been known\nin the rhizopods, and which the first to study it carefully, Felix\nDujardin, had described as _sarcode_ in 1835. Max Schultze further\nshowed that this \"sarcode\" was identical with the \"cell mucus\" of\nthe plant cells which Hugo Mohl had designated \"protoplasm\" in 1846,\nand that this living matter must be regarded as the real vehicle\nof the phenomena of life. As the membrane was now recognized to be\nnon-essential, of secondary growth, and completely wanting in some\ncases, there remained only two essential parts of the cell--the outer\nsoft cell body, consisting of protoplasm, and the inner firm nucleus,\nconsisting of a similar substance called nuclein. The original naked\ncell was now like a cherry or plum without the skin. This new idea of\nthe cell, formulated forty years ago, which I endeavored to confirm\nin my monograph on the radiolaria (1862), is now generally accepted,\nand the cell is defined as a granule or particle of protoplasm (=\ncytoplasm) enclosing a firm and definite nucleus (or caryon, consisting\nof caryoplasm).\n\nThis would be a good occasion to glance at the errors to which\nmicroscopic investigation and the conclusions based on it are liable.\nAlthough K\u00f6lliker in 1845, and Remak in 1851, had drawn attention to\nthe existence of naked cells, and had compared their movements (for\ninstance, in lymph-cells) to those of the protoplasm in plant-cells,\nthe majority of the leading microscopists clung for twenty years to\nthe dogma that every cell must have a membrane; the definite outline\nwhich even a naked cell must show in a different refracting medium was\ntaken to be the sign of a special and anatomically separable membrane.\nIt would be just as correct to talk of a protective membrane on a\nhomogeneous glass ball; its outline is sharply defined. In the long\ncontroversy that \"exact\" observers sustained as to the presence or\nabsence of a membrane, this optical error--the false interpretation\nof a sharp contour--counted for a good deal. It is much the same\nwith other conflicts of \"exact\" observers who give their \"certain\nobservations\" as facts, whereas they are really inferences from\nimperfect observations on which different interpretations may be put.\n\nForty years ago (1864) I tried in vain to detect a nucleus in the\nnaked, living, mobile protoplasm of a few small rhizopod-like protists\n(protam\u0153ba and protogenes). Other observers, who afterwards studied\nsimilar unnucleated cells (Gruber, Cienkowski, and others), were no\nmore successful. On the ground of these observations, which were often\nrepeated afterwards, I formed the class of the _monera_--the simplest\nunnucleated organisms--in my _General Morphology_ in 1866, and pointed\nout their great importance in solving some of the chief problems of\nbiology. This importance has been much enhanced of late, since the\nchromacea and bacteria have also been recognized as unnucleated cells.\nB\u00fctschli has, it is true, raised the objection that their homogeneous\nplasma-body behaves, not as cytoplasm, but as caryoplasm (or nuclein),\nand so that these simplest plastids correspond, not to the cell-body,\nbut to the nucleus of other cells. On this view the bacteria and\nchromacea are not cells without nuclei, but nuclei without cell-bodies.\nThis idea agrees with my own in conceiving the plasma-body of the\nmonera (apart from its molecular structure) as homogeneous and not yet\nadvanced as far as the characteristic differentiation of inner nucleus\nand outer cell-body. Bearing in mind that these essential parts of\nthe cell (in the view of most cytologists) are chemically related yet\ndifferent from each other, we have three possible cases of the original\nformation of the nucleated cell from the unnucleated cytode: (i) The\nnucleus and cell-body have arisen by differentiation of a homogeneous\nplasm (monera); (2) the cell-body is a secondary growth from the\nprimary nucleus; (3) the nucleus is a secondary development from the\ncell-body.\n\nOn the first view, which I hold, the plasm, or living matter, of\nthe earliest organisms on the earth (which can only be conceived as\narchigonous monera) was a homogeneous _plasson_ or archiplasm--that\nis to say, a plasma-compound that was not yet differentiated into\nouter cytoplasm and inner caryoplasm. The rise of this chemical\ndistinction--and the accompanying morphological division of cell-body\nand nucleus--was due to a phyletic differentiation; it was the outcome\nof a very early and most important division of labor. The hereditary\nmatter gathered in the nucleus, the outer cell-matter controlling the\nintercourse with the external world. Thus, by this first ergonomy, the\nnucleus became the vehicle of heredity and the cell-body the organ of\nadaptation. Opposed to this view is the second, the hypothesis which\nthe founder of the cell-theory, Schleiden, had put forward--that the\nnucleus is the original base of the cell, and the cell-body a secondary\ndevelopment from it. This opinion (which, in the main, corresponds\nto that of B\u00fctschli) raises a number of difficulties; as does also\nthe third hypothesis, that the unnucleated \"protoplasm-body\" (the\nouter cytoplasm-body) is the original formation, and that the nucleus\narose secondarily by condensation and chemical modification of it. At\nthe bottom, however, the difference between the three hypotheses on\nthe primary cytogenesis is not as great as it seems at first sight.\nHowever, I am more inclined to adhere to the first; it supposes\nthat the physiological and chemical differences between nucleus and\ncell-body, which afterwards became so important, were not originally\npresent. The phenomena of caryolysis in indirect cell-division show us\nstill how close are the relations of the two substances.\n\nIf the organic population of our planet has arisen naturally, and not\nby a miracle, as Reinke and other vitalists suppose, the earliest\nelementary organisms, produced by the chemical process of archigony\n(spontaneous generation), could not be real nucleated cells, but\nunnucleated cytodes of the type of the chromacea (_cf._ chapter ii.).\nThe nucleated real cell, as Oscar Hertwig and others define it to-day,\ncan only have arisen by phylogenetic differentiation of nucleus and\ncell-body from the simple cytode of the monera. In that case it is a\nmatter of simple logic to distinguish the older cytode from the later\ncell. The two may then best be comprised (as I proposed in vain in\n1866) under the name of \"plastids\" (formative principles)--that is,\nthe elementary organism in the broader sense. But if it is preferred\nto call the latter _cells_ (in the broader sense), the wrong modern\nidea of the cell must be altered, and the nucleus-feature omitted from\nit. The cell is then simply the living particle of plasm, and its two\nstages of development must be described by other names. The unnucleated\nplastid might be called _primitive cell_ (protocytos), and the ordinary\nnucleated one the nuclear cell (caryocytos).\n\nA long gradation of cellular organization leads from the simplest\nprimitive cells (monera) to the highest developed protists. While no\nmorphological organization whatever is discoverable in the homogeneous\nplasma-body of the chromacea and bacteria, we find a composition from\ndifferent parts in the highly differentiated body of the advanced\nprotophyta (diatomes, siphonea) and protozoa (radiolaria, infusoria).\nThe manifold parts of the unicellular organism, developed by division\nof work in the plasm, discharge various functions, and behave\nphysiologically like the organs of the multicellular histona. But\nas the idea of \"organ\" in the latter is morphologically fixed as a\nmulticellular part of the body, made up of numerous tissues, we cannot\ncall these similarly functioning parts \"organs of the cell,\" and had\nbetter describe them as organella (or organoids).\n\nThe great majority of the protists are, in the developed condition,\nas actual individuals, equivalent morphologically to real nucleated\ncells. By means of adaptation to the most varied conditions and\nthe inheritance of the properties thus acquired such a variety of\nunicellular forms has been evolved in the course of millions of\nyears that we can distinguish thousands of living species, both of\nplasmodomous protophyta and plasmophagous protozoa. The number of\nknown and named species is already as high as this in several distinct\nclasses, as, for instance, in the diatomes of the primitive plants\nand the radiolaria of the primitive animals. These solitary living\nunicellulars, or \"hermit-cells,\" may be called _monobia_.\n\nMany other protists have abandoned this original solitary life; they\nfollow their social instincts and form communities or colonies of cells\n(_c\u0153nobia_). These are usually formed by the daughter-cells which\narise from the cleavage of a mother-cell remaining united after the\ndivision, and so on with the succeeding generations which come from\ntheir repeated segmentation. The following are the chief forms of these\nc\u0153nobia:\n\n1. GELATINOUS C\u0152NOBIA.--The social cells secrete a structureless\nmass of jelly, and remain associated in the common gelatinous mass,\nwithout actual contact. Sometimes they are regularly, at other times\nirregularly, distributed in it. We find c\u0153nobia of this kind even\namong the monera, such as the _zoogl\u0153a_ of many bacteria and\nchromacea. They are common among the protophyta and protozoa.\n\n2. SPHERICAL C\u0152NOBIA.--The cell-community forms a sort of ball,\nthe cells lying close together at its surface, touching each other or\neven forming a continuous layer; such are _holosph\u00e6ra_ and _volvox_\namong the protophyta, _magosph\u00e6ra_ and _synura_ among the protozoa.\nThe latter are particularly interesting because they resemble the\n_blastula_, an important embryological stage of the metazoa, of which\nthe simple, epithelial cell-layer at the surface of the hollow sphere\nis called the _blastoderm_ (or germinal membrane).\n\n3. ARBOREAL C\u0152NOBIA.--The cell-community takes the form of a small\ntree or shrub, the fixed cells secreting jelly-like stalks at their\nbase and these forming branches. At the top of each stalk or branch\nis an independent cell; so in the case of the _gomphonema_ and many\nother diatomes, the _codonocladium_ among the flagellata, and the\n_carchesium_ among the ciliata.\n\n4. CATENAL C\u0152NOBIA.--The cell-community forms a chain, the links of\nwhich (the individual cells) are joined in a row. We find chainlike\ncell-communities of this sort, or \"articulated threads,\" even among the\nmonera (_oscillaria_ and _nostic_ among the chromacea, _leptothrix_\namong the bacteria). Among the diatomes we have the _bacillaria_, among\nthe thalamophora _nodosaria_, as examples. Many of the lower protophyta\n(algaria and algetta) form the direct transition to the true alg\u00e6 among\nthe metaphyta, as the threadlike layer of the latter (for instance,\n_cladophora_) is only a higher development of the catenal c\u0153nobium,\nwith polymorphism of the co-ordinated cells. We may also regard these\narticulated multicellular threads as the first sketch for the formation\nof tissues in the metaphyta.\n\nThe stable communities of cells which make up the body of the histona,\nor multicellular plants and animals, are called tissues (_tela_ or\n_hista_). They differ from the c\u0153nobia of the protists in that\nthe social cells give up their independence, assume different forms\nin the division of labor, and subordinate themselves to the higher\nunity of the organ. However, it would be just as difficult to lay\ndown a sharp limit between the c\u0153nobia and the tissues as between\nthe protists and the histona which possess them; the latter have been\ndeveloped phylogenetically from the former. The original physiological\nindependence of the cells which have combined to form tissues is more\ncompletely lost in proportion to the closeness of their combination,\nthe complexity of their division of labor, and the differentiation\nand centralization of the tissue-organism. Hence the various kinds of\ntissue in the body of the histona behave like the various classes and\nprofessions in a state. The higher the civilization and the more varied\nthe classes of workers, the more they are dependent on each other, and\nthe state is centralized.\n\nIn the lower tissue-forming plants, the alg\u00e6 and fungi, the plant-body\nhas the appearance of a layer of cells, the tissues of which show\nlittle or no division of labor. In these _thallophyta_ there are\nnone of the conducting or vascular fibres, the formation of which\nis of great importance in the higher plants in connection with\ntheir physiological function of circulation of the sap. These more\nadvanced vascular plants comprehend the two great groups of ferns\n(_pteridophyta_) and flowering plants (_anthophyta_, or phanerogams).\nTheir body is always composed of two chief organs, the axial stem\nand the lateral leaves. This is also the case with the mosses\n(_bryophyta_), which have no vascular fibres; they lie between the\ntwo chief groups of the non-vascular thallophyta and the vascular\ncormophyta. However, this histological and organological division of\nthe two great groups of tissue-plants must not be pressed; there are\nmany exceptions and intermediate forms. In general their manifold\ntissue-forms may be brought under two chief groups, which we may call\nprimary and secondary. The primary tissues are the phylogenetically\nolder and histologically simple \"cell-tissues,\" such as we have in the\nthallophyta (alg\u00e6, fungi, and mosses); in these there are no conducting\nfibres, or, at least, only rudimentary ones. The secondary tissues\nare a later development from these; they form conducting and vascular\nfibres and other highly differentiated forms of tissue (cambium, wood,\netc.). They make up the bodies of the more complex vascular plants, the\nferns and flowering plants.\n\nIn the bodies of the tissue-animals we may similarly distinguish two\nchief groups of tissues, the primary and secondary. The former are\nphylogenetically and ontogenetically older than the latter. The primary\ntissues of the metazoa are the _epitelia_, simple layers of cells or\nforms of tissue directly derived from such (glands, etc.). Secondary\ntissues, evolved from the former by physiological change of work and\nmorphological differentiation, are the _apotelia_; of these \"derivative\ntissues\" we may distinguish the three leading groups of connective\ntissue, muscular tissue, and nerve tissue. These three great groups of\ntissue in the animal world may be subdivided, like the plant groups,\ninto lower and higher sub-sections. The c\u0153lenteria (gastr\u00e6ads,\nsponges, cnidaria) are predominantly built up of epitelia, as are also\nthe phyletically older group of the c\u0153lomaria; in the vast majority\nof the latter, however, the great mass of the body is formed of\napotelia, and they are subject to the most extensive differentiation.\nThe embryo of all the metazoa consists solely of epitelia (the\ngerm-layers) at first; apotelia are developed from these afterwards by\ndifferentiation of the tissues.\n\nComparative anatomy distinguishes in the multicellular body of the\ntissue-forming organisms a great number of different parts, which are\nregularly adapted to discharge definite vital functions, and have been\nmost intricately developed in virtue of the division of labor. They are\ncalled \"organs\" in the stricter sense in opposition to the organella\n(or organoids) of the protists; the latter have, it is true, a similar\nphysiological purport, but are not (being parts of a cell) equal to the\nformer morphologically. The remarkable efficiency that we find in the\nstructure of the various organs in view of the functions they have to\ndischarge, and the regularity of their construction in the unity of\nthe histon--in other words, their adaptive organization--is explained\nmechanically by the theory of selection, while the teleological\nhypotheses of dualistic biology (for instance, the \"intelligent\ndominants\" of Reinke) completely fail to account for their origin. The\ngradual advance of the organs and their physiological division of labor\nhave many analogies in the two kingdoms of the histona. While at the\nlowest stages the simple organ represents only a separate individual\npiece of primitive tissue, we find special systems of organs and\norganic apparatus in the higher stages.\n\nThe idea of a particular system of organs is determined by the unity\nof one tissue which forms the characteristic element in the totality\nof the organs that belong to it. Of such systems in the kingdom of the\nmetaphyta we have: the skin-system (with the tissue of the epidermis),\nthe vascular system (with its conducting and vascular fibres), and the\ncomplementary tissue system (with the basic tissue). In the kingdom of\nthe metazoa we may similarly distinguish: the skin-system (integument\nof the epidermis), the vascular system (with the mesenchyma-tissue\nof the blood and blood-vessels), the muscular system (with the\nmuscle-tissue), and the nervous system (with the neurona of the\nnerve-tissue).\n\nIn contrast with the histological idea of a system of organs, we have\nthe physiological conception of an apparatus of organs. This is not\ndetermined by the unity of the constituent tissue, but by the unity of\nthe lifework that is accomplished by the particular group of organs in\nthe histona. Such an apparatus of organs is, for instance, the flowers\nand the fruit developing therefrom in the phanerogams, or the eye or\nthe gut of an animal. In these apparatus the most diverse organs and\nsystems of organs may be associated for the fulfilment of a definite\nphysiological task.\n\nIn the higher animals and plants we usually regard as the \"real\nindividual\" (in the wider sense of the word) the tissue-forming\norganism made up of various organs; and we may here briefly and\ninstructively call this the histonal individual (or, more briefly,\nthe \"histonal\"). Botanists call this individual phenomenon among\nthe metaphyta a sprout (_blastus_). Zoologists give the title of\n\"person\" (_prosopon_) to the corresponding unity among the animals.\nThe two forms agree very much in their general features, and may be\ncalled \"individuals of the second order,\" if we take the cells to be\nthe first and the stock the third stage in the hierarchy of organic\nindividuality. In comprising them here under the general head of\nhistonals, or histonal individuals, I mean by this to designate the\ndefinite physiological unity of the multicellular and tissue-forming\norganism, as contrasted with the unicellular protist on the one hand,\nand the higher stem, made up of several histonals, on the other.\n\nThe plant-histonal, which Alexander Braun especially clearly marked\nout and described as the sprout, is found in two principal forms in\nthe kingdom of the metaphyta--the lower form of the layer-sprout\n(_thallus_) and the higher form of the stalk-sprout (_culmus_).\nThe thallus predominates in the lower and older sub-kingdom of the\nlayer-plants (_thallophyta_), in the classes of the alg\u00e6 and fungi;\nthe culmus in the higher and younger sub-kingdom of the stalk-plants\n(_cormophyta_), in the classes of the mosses, ferns, and flowering\nplants. The culmus presents in general the characteristic form of\nan axial central organ, the stalk, with lateral organs, the leaves,\nattached to this at the sides, the former having an unlimited vertical\ngrowth and the latter an unlimited basal growth. The thallus does not\nyet show this important morphological division. There are, however,\nexceptions in both groups of the metaphyta. The large and highly\ndeveloped _fucoidea_ among the alg\u00e6 exhibit similar differentiations\nof organs to those we distinguish as stalk and leaves in the higher\ncormophyta. On the other hand, they are wanting in the lower\nliverworts, which form a thallus like many of the alg\u00e6; thus, for\ninstance, the liverwort _riccia fluitans_ is just like the brown\nalga _dictyota dichotoma_. Other primitive liverworts (such as the\n_anthoceros_) have also a very simple thallus; but most of them have\na separation of the thallus into an axial organ (stalk) and several\nlateral organs (leaves). In the distribution of labor among the\nleaves there then emerge the differences between the lower leaves,\nfoliage leaves, higher leaves, and flower leaves. A simple poppy-plant\n(_papaver_) or a single-flowered _gentiana ciliata_, which has only one\nbloom at the top of its branchless stalk, is a good example of a highly\ndeveloped culmus.\n\nTo the plant-sprout corresponds in the animal world the _person_. All\nthe tissue-animals pass in the course of their embryonic development\nthrough the important stage of the _gastrula_, or \"cup-shaped embryo.\"\nThe whole body of the tissue-animal at this stage forms at first a\nsimple gut-sac or gastric sac (the primitive gut), the cavity of\nwhich opens outward by a primitive mouth. The thin wall of the sac is\nformed by two superimposed layers of cells, the two primary germinal\nlayers. This gastrula is the simplest form of the \"person,\" and the two\ngerminal layers are its sole organs.\n\nThe diverse animal forms which develop along different lines\nfrom this common embryonic form of the gastrula may be grouped\ninto two sub-kingdoms, the lower (_c\u0153lenteria_) and the upper\n(_c\u0153lomaria_) animals. The former correspond in the simplicity of\ntheir structure in many respects to the thallophyta, and the latter\nto the cormophyta. Of the four stems of the c\u0153lenteria (which\nhave only a ventral opening and no gut-cavity) the gastr\u00e6ads remain\nat the gastrula stage, and the sponges are formed by multiplication\nof the same stems of gastr\u00e6ads. On the other hand, the cnidaria\ndevelop into higher radial (star-shaped) persons, and the platodes\ninto lower bilateral persons. From the latter are derived the worms\n(_vermalia_), the common stem-groups of the five higher animal stems,\nthe unarticulated mollusks, echinoderms, and tunicates, and the\nlimb-forming articulates and vertebrates.\n\nA large part of the physiological advantages and morphological\nperfection which the higher histona have, as contrasted with the lower,\nmay be traced to the circumstance that the tissue-forming organism\narticulates--that is to say, divides on its long axis into several\nsections. With this multiplication of groups of organs there goes, as a\nrule, a more or less extensive division of work among them, a leading\nfactor of higher development. In this point also we see the biogenetic\nparallelism between the two great groups of the tissue-plants and\ntissue-animals.\n\nIn the kingdom of the tissue-plants the articulated cormophyta rise\nhigh above the unarticulated thallophyta. While the articulation of\nthe stem of the former proceeds and leaves are developed at the knots\n(_nodi_) between each two sections of the stalk, far greater play is\noffered to polymorphic differentiation than in the thallophyta, which\nare generally without this metamerism. The formation of the bloom in\nthe flowering plants or phanerogams consists in a sexual division of\nlabor among the thickly gathered leaves in a short section of a stem.\n\nTo the two groups of unarticulated and articulated sprouts in the\nkingdom of the tissue-plants correspond, in many respects, the two\nsections of the tissue-animals, the unarticulated and the articulated.\nThe two stems of the articulates and vertebrates rise above all the\nother metazoa by the perfection of their organism and the variety\nof their functions. In the articulates the metamerism is chiefly\nexternal--an articulation of the body wall. In the vertebrates it\nmainly affects the internal organs, the skeleton, and the muscular\nsystem. The vertebration (articulation) of the vertebrates is not\noutwardly visible like that of the articulates. In both stems the\narticulation is similar in the lower and upper forms, as we find in\nthe annelids and myriapods, the acrania and cyclostoma. On the other\nhand, the higher the organization the greater is the unlikeness of\nthe members or articulated parts, as in the arachnida and insects,\nthe amphibia and amniotes. The same antithesis is found in the lower\nand higher crustacea. This metamerism of the higher metazoa is of a\nmotor character, having been acquired through the manner of movement\nof the lengthened body; but we find in some groups of the lower, and\nusually unarticulated, metazoa a propagative metamerism, determined\nby budding at the end; such is the strobilation of the chain-worms\nand the scyphostoma polyps. The individual metamera (parts) that are\nreleased from the end of the chain in these cases immediately show\ntheir individuality. This is also the case with many of the annelids,\nin which every member that is separated has the power to reproduce the\nwhole chain of metamera.\n\nThe third and highest stage of individuality to which the multicellular\norganism attains is the stock or colony (_cormus_). It is usually\nformed by a permanent association of histonals that are produced\nby cleavage (imperfect segmentation or budding) from one histonal\nindividual. The great majority of the metaphyta form complex plants in\nthis sense. But among the metazoa we find this form of individuality\nonly in the lower (and generally stationary) stages of development.\nHere also there is a striking parallelism of development between the\ntwo chief groups of the histona. At the lower stages of stock-formation\nthere is equality of the social histonals. But in the higher grades\nthey become unequally developed in the division of labor; and the\ngreater the differences between them become, the greater is the\ncentralization of the whole stock (as in the case of the siphonophora).\nWe may therefore distinguish two principal forms of stocks--the\nhomonomous and heteronomous, the one without, and the other with,\ndivision of labor among the histonals.\n\nThe history of civilization teaches us that its gradual evolution is\nbound up with three different processes: (1) Association of individuals\nin a community; (2) division of labor (ergonomy) among the social\nelements, and a consequent differentiation of structure (polymorphism);\n(3) centralization or integration of the unified whole, or rigid\norganization of the community. The same fundamental laws of sociology\nhold good for association throughout the entire organic world; and also\nfor the gradual evolution of the several organs out of the tissues\nand cell-communities. The formation of human societies is directly\nconnected with the gregariousness of the nearest related mammals. The\nherds of apes and ungulates, the packs of wolves, the flocks of birds,\noften controlled by a single leader, exhibit various stages of social\nformation; as also the swarms of the higher articulates (insects,\ncrustacea), especially communities of ants and termites, swarms\nof bees, etc. These organized communities of free individuals are\ndistinguished from the stationary colonies of the lower animals chiefly\nby the circumstance that the social elements are not bodily connected,\nbut held together by the ideal link of common interest.\n\n\n\n\nVIII\n\nFORMS OF LIFE\n\n Morphology--Laws of symmetry--Fundamental forms of animals\n and plants--Fundamental forms of protists and histona--Four\n chief classes of fundamental forms: (1) Centrostigma: vesicles\n (smooth vesicle and tabular vesicle); (2) Centraxonia: typical\n forms with central axis--Uniaxial (monaxonia, equipolar and\n unequipolar)--Transverse-axial (stauraxonia, double-pyramidal\n and pyramidal); (3) Centroplana: fundamental forms with\n central plane--Bilateral symmetry--Bilateral-radial and\n bilateral-symmetrical fundamental forms--Asymmetrical fundamental\n forms; (4) Anaxonia: irregular fundamental forms--- Causes of\n form-construction--Fundamental forms of monera, protists, and\n histona--Fundamental form and mode of life--Beauty of natural\n forms--\u00c6sthetics of organic forms--Art forms in nature.\n\n\nThe infinite variety of forms which we observe in the realm of organic\nlife not only delight our senses with their beauty and diversity, but\nalso excite our curiosity, in suggesting the problem of their origin\nand connection. While the \u00e6sthetic study of the forms of life provides\ninexhaustible material for the plastic arts, the scientific study of\ntheir relations, their structures, their origin and evolution, forms\na special branch of biology, the science of forms or morphology. I\nexpounded the principles of this science in my _General Morphology_\nthirty-eight years ago. They are so remote from the ordinary curriculum\nof education, and are so difficult to explain without the aid of\nnumerous illustrations, that I cannot think of going fully into\nthem here. In the present chapter I will only briefly describe those\nfeatures of living things which relate to the difficult question of\ntheir ideal fundamental forms, the laws of their symmetry, and their\nrelation to crystal-formation. I have treated these intricate questions\nsomewhat fully in the last (eleventh) part of _Art-forms in Nature_.\nThe hundred plates contained in this work may serve as illustrations of\nmorphological relations. In the following pages the respective plates\nare indicated by the letters A-f, with the number of each.\n\nThe unity of the organic structure, which expresses itself everywhere\nin the fundamental features of living things and in the chemical\ncomposition and constructive power of their plasm, is also seen in\nthe laws of symmetry in their typical forms. The infinite variety of\nthe species may, both in the animal and plant worlds, be reduced to\na few principal groups or classes of fundamental forms, and these\nshow no difference in the two kingdoms (_cf._ plate 6). The lily has\nthe same regular typical form as the hexaradial coral or anemone\n(A-f, 9, 49), and the bilateral-radial form is the same in the\nviolet and the sea-urchin (clypeaster, A-f, 30). The dorsiventral or\nbilateral-symmetrical form of most green leaves is repeated in the\nframe of most of the higher animals (the c\u0153lomaria); the distinction\nof right and left determines in each the characteristic antithesis of\nback and belly.\n\nThe distinction between protists and histons is much more important\nthan the familiar division of organisms into plants and animals, in\nrespect of their fundamental forms and their configuration. For the\nprotists, the unicellular organisms (without tissue) exhibit a much\ngreater freedom and variety in the development of their fundamental\nforms than the histons, the multicellular tissue-forming organisms. In\nthe protists (both protophyta and protozoa) the constructive force of\nthe elementary organism, the individual cell, determines the symmetry\nof the typical form and the special form of its supplementation; but in\nthe histons (both metaphyta and metazoa) it is the plasticity of the\ntissue, made up of a number of socially combined cells, that determines\nthis. On the ground of this tectological distinction we may divide\nthe whole organic world into four kingdoms (or sub-kingdoms), as the\nmorphological system in the seventh table shows.\n\nIn respect of the general science of fundamental forms (promorphology),\nthe most interesting and varied group of living things is the class\nof the radiolaria. All the various fundamental forms that can be\ndistinguished and defined mathematically are found realized in the\ngraceful flinty skeletons of these unicellular sea-dwelling protozoa.\nI have distinguished more than four thousand forms of them, and\nillustrated by one hundred and forty plates, in my monograph on the\n_Challenger_ radiolaria [translated].\n\nOnly a very few organic forms seem to be quite irregular, without any\ntrace of symmetry, or constantly changing their formless shape, as we\nfind, for instance, in the am\u0153b\u00e6 and the similar am\u0153boid cells\nof the plasmodia. The great majority of organic bodies show a certain\nregularity both in their outer configuration and the construction of\ntheir various parts, which we may call \"symmetry\" in the wider sense\nof the word. The regularity of this symmetrical construction often\nexpresses itself at first sight in the arrangement side by side of\nsimilar parts in a certain number and of a certain size, and in the\npossibility of distinguishing certain ideal axes and planes cutting\neach other at measurable angles. In this respect many organic forms\nare like inorganic crystals. The important branch of mineralogy that\ndescribes these crystalline forms, and gives them mathematical\nformul\u00e6, is called crystallography. There is a parallel branch of the\nscience of biological forms, promorphology, which has been greatly\nneglected. These two branches of investigation have the common aim of\ndetecting an ideal law of symmetry in the bodies they deal with and\nexpressing this in a definite mathematical formula.\n\nThe number of ideal fundamental forms, to which we may reduce the\nsymmetries of the innumerable living organisms, is comparatively\nsmall. Formerly it was thought sufficient to distinguish two or three\nchief groups: (1) radial (or actinomorphic) types, (2) bilateral (or\nzygomorphic) types, and (3) irregular (or amorphic) types. But when\nwe study the distinctive marks and differences of these types more\nclosely, and take due account of the relations of the ideal axes and\ntheir poles, we are led to distinguish the nine groups or types which\nare found in the sixth table. In this promorphological system the\ndetermining factor is the disposition of the parts to the natural\nmiddle of the body. On this basis we make a first distinction into four\nclasses or types: (1) the centrostigma have a _point_ as the natural\nmiddle of the body; (2) the centraxonia a straight line (axis); (3) the\ncentroplana a plane (median plane); and (4) the centraporia (acentra or\nanaxonia), the wholly irregular forms, have no distinguishable middle\nor symmetry.\n\n\n I. CENTROSTIGMATIC TYPES.--The natural middle of the body is a\n mathematical point. Properly speaking, only one form is of this\n type, and that is the most regular of all, the sphere or ball.\n We may, however, distinguish two sub-classes, the smooth sphere\n and the flattened sphere. The smooth sphere (_holosp\u0153ra_) is a\n mathematically pure sphere, in which all points at the surface are\n equally distant from the centre, and all axes drawn through the\n centre are of equal length. We find this realized in its purity\n in the ovum of many animals (for instance, that of man and the\n mammals) and the pollen cells of many plants; also cells that\n develop freely floating in a liquid, the simplest forms of the\n radiolaria (_actissa_), the spherical c\u0153nobia of the volvocina\n and catallacta, and the corresponding pure embryonic form of the\n _blastula_. The smooth sphere is particularly important, because it\n is the only absolutely regular type, the sole form with a perfectly\n stable equilibrium, and at the same time the sole organic form which\n is susceptible of direct physical explanation. Inorganic fluids\n (drops of quicksilver, water, etc.) similarly assume the purely\n spherical form, as drops of oil do, for instance, when put in a\n watery fluid of the same specific weight (as a mixture of alcohol and\n water).\n\n The flattened sphere, or facetted sphere (_platnosph\u00e6ra_), is known\n as an endospherical polyhedron; that is to say, a many-surfaced body,\n all the corners of which fall in the surface of a sphere. The axes\n or the diameters, which are drawn through the angles and the centre,\n are all unequal, and larger than all other axes (drawn through the\n facets). These facetted spheres are frequently found in the globular\n silicious skeletons of many of the radiolaria; the globular central\n capsule of many spheroidea is enclosed in a concentric gelatine\n envelope, on the round surface of which we find a net-work of fine\n silicious threads. The meshes of this net are sometimes regular\n (generally triangular or hexagonal), sometimes irregular; frequently\n starlike silicious needles rise from the knots of the net-work (A-f,\n 1, 51, 91). The pollen bodies in the flower-dust of many flowering\n plants also often assume the form of facetted spheres.\n\n II. CENTRAXONIA TYPES.--The natural middle of the body is a straight\n line, the principal axis. This large group of fundamental forms\n consists of two classes, according as each axis is the sole fixed\n ideal axis of the body, or other fixed transverse axes may also\n be distinguished, cutting the first at right angles. We call the\n former uniaxial (_monaxonia_), and the latter transverse-axial\n (_stauraxonia_). The horizontal section (vertically to the chief\n axis) is round in the uniaxials and polygonal in the transverse-axial.\n\n In the monaxonia the form is determined by a single fixed axis,\n the principle axis; the two poles may be either equal (_isopola_)\n or unequal (_allopola_). To the isopola belong the familiar simple\n forms which are distinguished in geometry as spheroids, biconvex,\n ellipsoids, double cones, cylinders, etc. A horizontal section,\n passing through the middle of the vertical chief axis, divides the\n body into two corresponding halves. On the other hand, many of the\n parts are unequal in size and shape in the _allopola_. The upper pole\n or vertex differs from the basal pole or ground surface; as we find\n in the oval form, the planoconvex lens, the hemisphere, the cone,\n etc. Both sub-classes of the monaxonia, the allopola (conoidal) and\n the isopola (spheroidal), are found realized frequently in organic\n forms, both in the tissue-cells of the histona and the independently\n living protists (A-f, 4, 84).\n\n In the stauraxonia the vertical imaginary principal axis is cut by\n two or more horizontal cross-axes or radial-axes. This is the case in\n the forms which were formerly generally classed as regular or radial.\n Here also, as with the monaxonia, we may distinguish two sub-classes,\n isopola and allopola, according as the poles of the principal axis\n are equal or unequal.\n\n Of the _stauraxonia isopola_ we have, for instance, the double\n pyramids, one of the simplest forms of the octahedron. This form is\n exhibited very typically by most of the acantharia, the radiolaria\n in which twenty radial needles (consisting of silicated chalk) shoot\n out from the centre of the vertical chief axis. These twenty rays\n are (if we imagine the figure of the earth with its vertical axis)\n distributed in five horizontal zones, with four needles each, in\n this wise: two pairs cross at right angles in the equatorial zone,\n but on each side (in north and south hemispheres) the points of four\n needles fall in the tropical zone, and the points of four polar\n needles in the polar circles; twelve needles (the four equatorial\n and eight polar) lie in two meridian planes that are vertical to\n each other; and the eight tropical needles lie in two other meridian\n planes which cross the former at an angle of forty-five degrees.\n In most of the acantharia (the radial acanthometra and the mailed\n acanthophracta)--there are few exceptions--this remarkable structural\n law of twenty radial needles is faithfully maintained by heredity.\n Its origin is explained by adaptation to a regular attitude which\n the sea-dwelling unicellular body assumes in a certain stage of\n equilibrium (A-f, 21, 41). If the points of the real needles are\n connected by imaginary lines, we get a polyhedrical body, which may\n be reduced to the form of a regular double pyramid. This typical form\n of the equipolar stauraxonia is also found in other protists with a\n plastic skeleton, as in many diatomes and desmidiacea (A-f, 24). It\n is more rarely found embodied in the tissue-cells of the histona.\n\n Unequipolar stauraxonia are the pyramids, a fundamental form that\n plays an important part in the configuration of organic bodies. They\n were formerly described as regular or fundamental forms. Such are the\n regular blooms of flowering plants, the regular echinoderms, medus\u00e6,\n corals, etc. We may distinguish several groups of them according to\n the number of the horizontal transverse axes that cut the vertical\n main axis in the middle.\n\n Two totally different divisions of the pyramidal types are the\n regular and the amphithecta pyramids. In the regular pyramids the\n transverse axes are equal, and the ground-surface (or base) is a\n regular polygon, as in the three-rayed blooms of the iris and crocus,\n the four-rayed medus\u00e6 (A-f, 16, 28, 47, 48, etc.), the five-rayed\n \"regular echinoderms,\" most of the star-fish, sea-urchins, etc. (A-f,\n 10, 40, 60), and the six-rayed \"regular corals\" (A-f, 9, 69).\n\n The amphithecta (or two-edged) pyramids, a special group of\n pyramidal types, are characterized by having as their basis a\n rhombus instead of a regular polygon. We may, therefore, draw two\n imaginary transverse axes, vertical to each other, through the\n ground-surface, both equipolar, but of unequal length. One of the\n two may be called the sagittal axis (with dorsal and ventral pole),\n and the other the transverse axis (with right and left pole); but\n the distinction is arbitrary, as the two are equipolar. In this lies\n the chief difference from the centroplane and dorsiventral forms, in\n which only the lateral axis is equipolar, the sagittal axis being\n unequipolar. We find the bisected pyramid in a very perfect form in\n the class of the ctenophora (or comb-medus\u00e6, A-f, 27), where it is\n quite general. The striking typical form of these pelagic cnidaria\n is sometimes called biradial, sometimes four-rayed and bilateral,\n and sometimes eight-rayed-symmetrical. Closer study shows it to be a\n rhombus-pyramid. The originally four-rayed type, which it inherited\n from craspedote medus\u00e6, has become bilateral by the development of\n different organs to the right and left from those before and behind.\n\n Similar rhombo-pyramidal forms to those of the ctenophora are also\n found in some of the medus\u00e6 and siphonophora, many of the corals and\n other cnidaria, and many flowers. The name \"two-edged\" which is given\n to this special type is taken from the ancient two-edged sword. Its\n chief axis is unequipolar, the handle being at the basic pole and\n the point at the verticle pole; but the two edges left and right are\n equal (poles of the lateral axis), and also the two broad surfaces\n (dorsal and ventral, joined by the sagittal axis).\n\n III. CENTROPLANE TYPES.--The natural middle of the body is a plane,\n the median or chief plane (_planum medianum_ or _sagittale_); it\n divides the bilateral body into two symmetrical halves, the right\n and the left. With this is associated the characteristic antithesis\n of back (_dorsum_) and belly (_venter_); hence, in botany this\n type (found, for instance, in most green leaves) is called the\n dorsiventral, and in zoology the bilateral in the narrower sense. One\n characteristic of this important and wide-spread type is the relation\n of three different axes, vertical to each other; of these three\n straight axes (enthyni) two are unequipolar and the third equipolar.\n Hence, the centroplanes may also be called tri-axial (_triaxonia_).\n In most of the higher animals (as in our own frame) the longest of\n the three axes is the principal one (_axon principalis_); its fore\n pole is the oral or mouth pole, and its hinder pole is the aboral\n or caudal (tail) pole. The shortest of the three enthyni is, in our\n body, the sagittal (arrow) or dorsiventral axis; its upper pole is\n at the back and its lower pole at the belly. The third axis--the\n transverse or lateral axis--is equipolar, one pole being called the\n right and the other the left. The various parts which make up the two\n halves of the body have relatively the same disposition in each half;\n but absolutely speaking (namely, in relation to the middle plane)\n they are oppositely arranged.\n\n Further, the centroplane or bilateral forms are also characterized\n by three vertical axes which may be drawn through each of the normal\n axes. The first of these normal planes is the median plane; it is\n defined by the chief axis and the sagittal axis, and divides the body\n into two symmetrical halves, the right and left. The second normal\n plane is the frontal plane; this passes through the chief axis and\n the transverse axis (which is parallel to the frontal surface in\n our body), and divides the dorsal half from the ventral half. The\n third normal plane is the cingular (waist) plane: this is defined by\n the sagittal and transverse axes. It divides the head half (or the\n vertical part) from the tail half (or the basal part).\n\n The name \"bilateral symmetry,\" which is especially applied to the\n centroplane and dorsiventral types, is ambiguous, as I pointed out\n in 1866 in an exhaustive analysis and criticism of these fundamental\n forms in the fourth book of the _General Morphology_. It is used in\n five different senses. For our present general purpose it suffices to\n distinguish two orders of centroplane types, the bilateral-radial and\n the bilateral-symmetrical; in the former the radial (pyramidal) form\n is combined with the bilateral, but not in the latter.\n\n The bilateral-radial type comprises those forms in which the radial\n structure is combined in a very characteristic fashion with the\n bilateral. We have striking examples in the three-rayed flowers\n of the orchids (A-f, 74), the five-rayed blooms of the labiate\n and papilionaceous flowers, etc., in the plant world; and in the\n five-rayed \"irregular\" echinoderms, the bilateral sea-urchins\n (spatangida, clypeastrida, A-f, 30) in the animal world. In these\n cases the bilateral symmetry is recognizable at the first glance, as\n is also the radial structure, or the composition from three to five\n or more raylike parts (paramera), which are arranged bilaterally\n round a common central plane.\n\n The bilateral-symmetrical type is general among the higher animals\n which move about freely. The body consists of two antithetic parts\n (_antimera_), and has no trace of radial structure. In the free\n moving, creeping, or swimming animals (vertebrates, articulates,\n mollusks, annelids, etc.) the ventral side is underneath, against the\n ground, and the dorsal side upward. This form is clearly the most\n useful and practical of all conceivable types for the movement of\n the body in a definite direction and position. The burden is equally\n distributed between the two sides (right and left); the head (with\n the sense organs, the brain, and the mouth) faces frontward and the\n tail behind. For thousands of years all artificial vehicles (carts on\n land and ships in water) have been built on this type. Selection has\n recognized it to be the best and preserved it, while it has discarded\n the rest. There are, however, other causes that have produced the\n predominance of this type in green leaves--the relation to the\n supporting stalk, to the sunlight that falls from above, etc.\n\nSpecial notice must be taken of those bilateral forms which were\noriginally symmetrical (by heredity), but have subsequently become\nasymmetrical (or of unequal halves), by adaptation to special\nconditions of life. The most familiar example among the vertebrates\nare the flat-fishes (_pleuronectides_), soles, flounders, turbots,\netc. These high and narrow and flattened boney-fishes have a perfect\nbilateral symmetry when young, like ordinary fishes. Afterwards they\nform the habit of laying on one side (right or left) at the bottom of\nthe sea; and in consequence the upper side, exposed to the light, is\ndark colored, and often marked with a design (sometimes very like the\nstony floor of the ocean--a protective coloring), while the side the\nflat-fish lies on remains without color. But, what is more curious,\nthe eye from the under side travels to the upper side, and the two\neyes lie together on one side (the right or left); while the bones of\nthe skull and the softer parts of each side of the head grow quite\ncrooked. Naturally, this ontogenetic process, in which a striking lack\nof symmetry succeeds to the early complete symmetry of each individual,\ncan only be explained by our biogenetic law; it is a rapid and brief\nrecapitulation (determined by heredity) of the long and slow phyletic\nprocess which the flat-fish has undergone for thousands of years in its\nancestral history to bring about its gradual modification. At the same\ntime, this interesting metamorphosis of the _pleuronectides_ gives us\nan excellent instance of the inheritance of acquired characteristics,\nas a consequence of constant \u0153cological habit. It is quite\nimpossible to explain it on Weismann's theory of the germ-plasm.\n\nWe have another striking example among the invertebrates in the snails\n(_gasteropoda_). The great majority of these mollusks are characterized\nby the spiral shape of their shells. This variously shaped, and often\nprettily colored and marked, snail's house is in essence a spirally\ncoiled tube, closed at the upper end and open at the lower (or mouth):\nthe mollusk can at any moment withdraw into its tube. The comparative\nanatomy and ontogeny of the snails teach us that this spiral shell\ncame originally from a simple discoid or cylindrical dorsal covering\nof the once bilateral-symmetrical mollusk, by the two sides of the\nbody having an unequal growth. The cause of it was a purely mechanical\nfactor--the sinking of the growing visceral sac, covered with the\nshell, to one side; one part of the viscera contained in it (the\nheart, kidneys, liver, etc.) grew more strongly on one side than the\nother in consequence of this; and this was accompanied by considerable\ndisplacement and modification of the neighboring parts, especially the\ngills. In most snails one of the gills and kidneys and the ventricle\nof the heart corresponding to these have disappeared altogether,\nonly those of the opposite side remaining; and the latter have moved\nfrom the right side to the left, or vice versa. The conspicuous lack\nof symmetry between the two halves of the body which resulted from\nthis finds expression in the spiral form of the snail's shell. This\nremarkable ontogenetic metamorphosis also can be fully explained by a\ncorresponding phylogenetic process, and affords a very fine instance of\nthe inheritance of acquired characters.\n\nThere are also many examples of this asymmetry of bilateral forms in\nthe plant world, such as the green foliage-leaves of the familiar\nbegonia and the blooms of _canna_.\n\nIV. THE CENTRAPORIA.--Few organic forms are completely irregular and\nwithout axes, as usually the attraction to the earth (geotaxis) or to\nthe nearest object determines the special direction of growth, and so\nthe formation of an axis in some direction or other. Nevertheless,\nwe may instance as quite irregular the soft and ever-changing\nplasma-bodies of many rhizopods, the am\u0153bin\u00e6, mycetozoa, etc. Most\nof the sponges also--which we regard as stocks of gastr\u00e6ads--are\ncompletely irregular in structure; the most familiar example is the\ncommon bath-sponge.\n\nAn impartial and thorough study of organic forms has convinced me that\ntheir actual, infinitely varied configurations may all be reduced\nto the few typical forms I have described. Comparative anatomy and\nontogeny further teach us that the countless modifying processes\nwhich have led to the appearance of the various species have acted by\nadaptation to different environments, habits, and customs, and give\nus, in conjunction with heredity, a physiological explanation of this\nmorphological transformation. But the question arises as to the origin\nof these few geometrically definable types, and the cause of their\ndivergence.\n\nIn this important and difficult question we find a great variety\nof opinions and a strong leaning to dualistic and mystic theories.\nEducated laymen, who have only a partial and imperfect acquaintance\nwith the biological facts, think that they are justified here in\nappealing to a supernatural creation of forms. They contend that only a\nwise creator, following a rational and conscious design, could produce\nsuch structures. Even distinguished and informed scientists lean in\nthis matter towards mystic and transcendental ideas; they believe that\nthe ordinary natural forces do not suffice to explain these phenomena,\nand that at least for the first construction of these fundamental types\nwe must postulate a deliberate creative thought, a design, or some such\nteleological cause, and therefore consciously acting final causes. So\nsay N\u00e4geli and Alexander Braun.\n\nIn direct opposition to this, I have ever maintained the view that the\naction of familiar physical forces--mechanical efficient causes--fully\nsuffices to explain the origin and transformation of these fundamental\ntypes, as well as for all other biological and inorganic processes. In\norder to understand this monistic position thoroughly, and to meet the\nerrors of dualism, we must bear in mind always the radical processes of\ngrowth which control all organic and inorganic configuration, and also\nthe long chain of advancing stages of development, which lead us from\nthe simplest protists, the monera, to the most advanced organisms.\n\nThe unicellular organisms exhibit the greatest variety from the\npromorphological point of view. In the single class of the radiolaria\nwe find all imaginable geometrical types represented. This is seen\nin a glance at the one hundred and forty plates on which I have\ndepicted thousands of these graceful little protozoa in my monograph\n(_Challenger Report_, vol. xviii.). On the other hand, the monera, at\nthe lowest stage of organic life, the structureless organisms without\norgans that live on the very frontier of the inorganic world, are very\nsimple. Especially interesting in this connection are the chromacea,\nwhich have hitherto been so undeservedly and so incomprehensibly\nneglected. Among the well-known and widely distributed chroococcacea,\nthe chroococcus, c\u0153losph\u00e6rium, and aphanocapsa are quite the most\nprimitive of all organisms known to us--and at the same time the\norganisms that enable us best to understand the origin of life by\nspontaneous generation (archigony). The whole organism is merely a\ntiny, bluish-green globule of plasm, without any structure, or only\nsurrounded by a thin membrane; its fundamental form is the simplest of\nall, the centraxial smooth sphere. Next to these are the oscillaria\nand nostochina, social chromacea, which have the appearance of thin,\nbluish-green threads. They consist of simple primitive (unnucleated)\ncells joined to each other; they seem often to be flattened into a\ndiscoid shape as a result of close conjunction. Many protists are found\nin two conditions, one mobile with very varied and changeable forms,\nand one stationary with a globular shape. But when the separate living\ncell begins to form a firm skeleton or protective cover for itself,\nit may assume the most varied and often most complicated forms. In\nthis respect the class of the radiolaria among the protozoa, and the\nclass of the diatomes among the protophyta (both of which have flinty\nshells), surpass all the other groups of the diversified realm of the\nprotists. In my _Art-forms in Nature_ I have given a selection of their\nmost beautiful forms (diatomes, A-f, 4, 84; radiolaria, A-f, 1, 11, 21,\n22, 31, 41, 51, 61, 71, 95). The most remarkable and most important\nfact about them is that the artistic builders of these wonderful and\noften very ingenious and intricate flinty structures are merely the\nplastidules or micella, the molecular and microscopically invisible\nconstituents of the soft viscous plasm (sarcode).\n\nThe configuration of the histona differs essentially from that of\nthe protists, since in the case of the latter the simple unicellular\nbody produces for itself alone the whole form and vital action of the\norganism, while in the histona this is done by the cell state, or the\nsocial combination of a number of different cells, which make up the\ntissue body. Hence the ideal type which we can always define in the\nactual histonal form has quite a different significance from that in\nthe unicellular protists. In the latter we find the utmost diversity in\nthe configuration of the independent living cells and the protective\ncover it forms; among the histona the number of fundamental forms\nis limited. It is true that the cells themselves which make up the\ntissues may exhibit a great variety in form and structure; but the\nnumber of the different tissues which they make up is small, and so\nis the number of ideal types exhibited by the organism they combine\nto form--the sprout (_culmus_) in the plant kingdom and the person in\nthe animal kingdom. The same may be said of the stock (_cormus_) in\nboth kingdoms--that is to say, of the higher individual unity which is\nconstituted by the union of several sprouts or persons.\n\nThe two classes of fundamental forms which are especially found in the\nplant sprouts or the animal persons are the radial and bilateral. The\none is determined by the stationary life, the other by free movement in\na certain attitude and direction (swimming in water or creeping on the\nground). Hence we find the radial form (as pyramidal) predominant in\nthe blooms and fruits of the metaphyta, and the persons of the polyps,\ncorals, and regular echinoderms. On the other hand, the bilateral or\ndorsiventral form preponderates in most free-moving animals; though\nit is also found in many flowers (papilionaceous and labial flowers,\norchids, and others that are fertilized by insects). Here we have\nto seek the cause of the bilateralism in different features, in the\nrelations with the insects, in the mode of their fastening to and\ndistribution on the stalk (for the green foliage leaves), and so on.\n\nThe complex individuals of the first order, the stocks (_cormi_), are\nmore dependent in their growth on the spatial conditions of their\nenvironment than the sprouts or persons; hence their typical form is\ngenerally more or less irregular, and rarely bilateral.\n\nThe interest which we take in natural and artistic forms, and which\nhas for thousands of years prompted men to reproduce the former in\nthe latter, depends for the most part, if not altogether, on their\nbeauty--that is to say, on the feeling of pleasure we experience in\nlooking at them. The causes of this pleasure and joy in the beautiful\nand the naturalness of its development are explained in \u00e6sthetics. When\nwe combine this science with the results of modern cerebral physiology,\nwe may distinguish two classes of beauty--direct and indirect. In\ndirect or sensible beauty the internal sense-organs, or the \u00e6sthetic\nneurona or sense-cells of the brain, are immediately affected with\npleasure. But in indirect or associational beauty these impressions\nare combined with an excitement of the phronetic neurona--the rational\nbrain-cells which effect presentation and thought.\n\nDirect or sensible beauty (the subject of sensual \u00e6sthetics) is the\ndirect perception of agreeable stimuli by the sense-organs. We may\ndistinguish the following stages of its perfection: 1. Simple beauty\n(the subject of primordial \u00e6sthetics); the pleasure is evoked by the\ndirect sense-impression of a simple form or color. Thus, for instance,\na wooden sphere makes an agreeable impression as compared with a\nshapeless piece of wood, a crystal as compared with a stone, a sky-blue\nor golden-yellow spot as compared with a greenish-blue or dull-yellow\none (in music a simple pure bell-tone as compared with a shrill\nwhistle). 2. Rhythmic beauty (the subject of linear \u00e6sthetics); the\n\u00e6sthetic sensation is caused by the serial repetition of some simple\nform--for instance, a pearl necklace, a chainlike community of monera\n(nostoc) or of cells (diatomes, A-f, 84, figs. 7 and 9): in music a\ntasteful series of simple notes. 3. Actinal beauty (the subject of\nradial \u00e6sthetics); the pleasure is excited by the orderly arrangement\nof three or more homogeneous simple forms about a common centre, from\nwhich they radiate; for instance, a regular cross or a radiating\nstar, the three counter-pieces in the iris-bloom, the four paramera\nin the body of the medusa, the five radial-pieces in the star-fish.\nThe familiar experience of the kaleidoscope shows how amply the simple\nradial constellation of three or more simple figures may delight\nour \u00e6sthetic sense (in music we have the simple harmony of several\nsimultaneous notes). 4. Symmetrical beauty (the subject of bilateral\n\u00e6sthetics); the pleasure is caused by the relation of a simple object\nto its like, the mutual completion of two similar halves (the right and\nleft parts). When we fold a piece of paper over an ink-stain in such a\nway that it is equally impressed on both halves of the fold, we get a\nsymmetrical figure which makes an agreeable impression on our natural\nsense of space or equilibrium.\n\nThe \u00e6sthetic impressions in indirect associational beauty (the subject\nof associative or symbolical \u00e6sthetics) are not only much more varied\nand complex than those we have described, but they also play a much\nmore important part in the life of man and the higher animals. The\nanatomic condition for this higher physiological function is the\nelaborate construction of the brain in the higher animals and man,\nand particularly the development of the special association-centres\n(thought-centres, reason-sphere) and their differentiation from the\ninternal sense-centres. In this millions of different neurona or\npsychic cells co-operate, the sensual \u00e6stheta acting in conjunction\nwith the rational phroneta, and thus, by complex associations of\nideas, much higher and more valuable functions arise. We may indicate\nfour chief groups of this associational or indirect beauty. 5.\nBiological beauty (the subject of botanical and zoological \u00e6sthetics):\nthe various forms of organisms and their organs (for instance, a\nflower, a butterfly) excite our \u00e6sthetic interest by association with\ntheir physiological significance, their movements, their bionomic\nrelations, their practical use, and so on. 6. Anthropistic beauty\n(the subject of anthropomorphic \u00e6sthetics): man, as \"the measure of\nall things,\" regards his own organism as the chief object of beauty,\neither morphologically considered (beauty of the whole body and\nits various organs--the eyes, mouth, hair, flesh-tint, etc.), or\nphysiologically (beauty of movements or positions), or psychologically\n(the expression of the emotions in the physiognomy). As man transfers\nto the objective world this personal gratification he experiences from\nself-consideration, and anthropomorphically regards other beings in\nthe light of them, this anthropistic \u00e6sthetic obtains a far-reaching\nsignificance. 7. Sexual beauty (the subject of erotic \u00e6sthetics): the\npleasure is caused by the mutual attraction of the sexes. The supreme\nimportance of love in the life of man and most other organisms,\nthe powerful influence of the passions, the sexual selection that\nis associated with reproduction, have evoked an infinite number of\n\u00e6sthetic creations in every branch of art relating to the antithesis of\nman and woman. The special pleasure which is caused by the bodily and\nmental affinities of the sexes can be traced phylogenetically to the\ncell-love of the two sexual cells, or the attraction of the sperm-cell\nto ovum. 8. Landscape beauty (the subject of regional \u00e6sthetics): the\npleasure which is caused by the sight of a fine landscape, and that\nfinds satisfaction in modern landscape-painting, is more comprehensive\nthan that of any other \u00e6sthetic sensations. In point of space the\nobject is larger and richer than any of the individual objects in\nnature which are beautiful and interesting in themselves. The varying\nforms of the clouds and the water, the outline of the blue mountains\nin the background, the woods and meadows in the middle-distance,\nand the living figures in the foreground, excite in the mind of the\nspectator a number of different impressions which are woven together\ninto a harmonious whole by a most elaborate association of ideas. The\nphysiological functions of the nerve-cells in the cortex which effect\nthese \u00e6sthetic pleasures, and the interaction of the sensual \u00e6stheta\nwith the rational phroneta, are among the most perfect achievements\nof organic life. This \"regional \u00e6sthetics,\" which has to establish\nscientifically the laws of landscape beauty, is much younger than the\nother branches of the science of the beautiful. It is very remarkable\nthat absolute irregularity, the absence of symmetry and mathematical\nforms, is the first condition for the beauty of a landscape (as\ncontrasted with architecture, and the beauty of separate objects in\nnature). Symmetrical arrangement of things (such as a double row of\npoplars or houses) or radial figures (a flower-bed or artificial wood)\ndo not please the finer taste for landscape; they seem tedious.\n\nA comparative survey of these eight kinds of beauty in natural forms\ndiscovers a connected development, rising from the simple to the\ncomplex, from the lower to the higher. This scale corresponds to the\nevolution of the sense of beauty in man, ontogenetically from the\nchild to the adult, phylogenetically from the savage to the civilized\nman and the art critic. The stem-history of man and his organs, which\nexplains to us in anthropogeny the gradual rise from lower to higher\nforms by the interaction of heredity and adaptation, also finds an\napplication in the history of \u00e6sthetics and ornamentation. It teaches\nus how feeling, taste, emotion, and art have been gradually evolved. On\nthe other hand, we have corresponding to this evolutionary series the\nscale of the typical forms which lie at the root of the real forms of\nbodies both in nature and art.\n\n\n\n\nSEVENTH TABLE\n\nTHE MORPHOLOGICAL SYSTEM OF ORGANISMS\n\nDivision of living things (plants and animals) into two kingdoms\n(protista and histona) on the ground of their cell-structure and\nbody-structure.\n\n\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n \u2502 First organic kingdom: UNICELLULAR, protista. \u2502\n \u2502 \u2502\n \u2502Organisms which as a rule remain unicellular \u2502\n \u2502throughoutlife (_monobia_), less frequently they \u2502\n \u2502form loose cell communities (_c\u0153nobia_) by \u2502\n \u2502repeated cleavage, but never real tissues. \u2502\n \u2502 \u2502\n \u2502 Sub\u2500kingdom of the protista. \u2502\n \u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2524\n \u2502 A. PRIMITIVE PLANTS \u2502 B. PRIMITIVE ANIMALS \u2502\n \u2502 (protophyta). \u2502 (protozoa). \u2502\n \u2502 \u2502 \u2502\n \u2502 A. Character: \u2502 B. Character: \u2502\n \u2502 Plasmodomous. \u2502 Plasmophagous. \u2502\n \u2502 \u2502 \u2502\n \u2502 Unicellulars with \u2502 Unicellulars with \u2502\n \u2502 vegetal metabolism: \u2502 animal metabolism: \u2502\n \u2502 Carbon\u2500assimilation. \u2502 Albumin\u2500assimilation. \u2502\n \u2502 \u2502 \u2502\n \u2502 CHIEF GROUPS: \u2502 CHIEF GROUPS: \u2502\n \u2502 \u2502 \u2502\n \u2502 I. Phytomonera \u2502 I. Zoomonera. \u2502\n \u2502 \u2502 \u2502\n \u2502Protophyta without nucleus \u2502 Protozoa without nucleus \u2502\n \u2502 (monera) \u2502 (monera). \u2502\n \u2502 Chromacea \u2502 Bacteria. \u2502\n \u2502 \u2502 \u2502\n \u2502 II. Algari\u00e6. \u2502 II. Sporozoa. \u2502\n \u2502 \u2502 \u2502\n \u2502Unicellular alg\u00e6 with \u2502 Nucleated protozoa without \u2502\n \u2502nucleus, without ciliary \u2502 mobile processes: Gregarin\u00e6, \u2502\n \u2502motion: Paulotomea, \u2502 chytridin\u00e6. \u2502\n \u2502diatomea. \u2502 \u2502\n \u2502 \u2502 \u2502\n \u2502 III. Algett\u00e6. \u2502 III. Rhizopoda. \u2502\n \u2502 \u2502 \u2502\n \u2502Unicellular alg\u00e6 with \u2502 Nucleated protozoa with \u2502\n \u2502nucleus, and with ciliary \u2502 pseudopodia: Labosa, \u2502\n \u2502motion: Mastigota, \u2502 radiolaria. \u2502\n \u2502melthallia, siphonea. \u2502 \u2502\n \u2502 \u2502 IV. Infusoria. \u2502\n \u2502 \u2502 \u2502\n \u2502 \u2502 Nucleated protozoa with \u2502\n \u2502 \u2502 cilia or lashes: \u2502\n \u2502 \u2502 Flagellata, ciliata. \u2502\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n\n\n \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n \u2502 Second organic kingdom: MULTICELLULAR, histona. \u2502\n \u2502 \u2502\n \u2502 Organisms which are only unicellular at the \u2502\n \u2502 beginning of their existence, are later \u2502\n \u2502 multicellular, and always form real tissues \u2502\n \u2502 (_histobia_) by the firm conjunction of social cells. \u2502\n \u2502 \u2502\n \u2502 Sub\u2500kingdom of the histona. \u2502\n \u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2524\n \u2502 C. TISSUE PLANTS \u2502 D. TISSUE ANIMALS \u2502\n \u2502 (metaphyta). \u2502 (metazoa). \u2502\n \u2502 \u2502 \u2502\n \u2502 C. Character: \u2502 D. Character: \u2502\n \u2502 Plasmodomous. \u2502 Phasmophagous. \u2502\n \u2502 \u2502 \u2502\n \u2502 Multicellulars with \u2502 Multicellulars with \u2502\n \u2502 vegetal metabolism: \u2502 animal metabolism: \u2502\n \u2502 Carbon\u2500assimilation. \u2502 Albumin\u2500assimilation. \u2502\n \u2502 \u2502 \u2502\n \u2502 CHIEF GROUPS: \u2502 CHIEF GROUPS: \u2502\n \u2502 \u2502 \u2502\n \u2502 I. Thallophyta. \u2502 I. C\u0153lenteria \u2502\n \u2502 \u2502 (c\u0153lenterata). \u2502\n \u2502 Thallus\u2500plants. Metaphyta \u2502 \u2502\n \u2502 with thallus: Alg\u00e6, mycet\u00e6 \u2502 Metazoa without body \u2502\n \u2502 (fungi). \u2502 cavity and anus: Gastr\u00e6ada. \u2502\n \u2502 \u2502 Sponges, cnidaria, platodes. \u2502\n \u2502 II. Mesophyta. \u2502 \u2502\n \u2502 \u2502 II. C\u0153lomaria \u2502\n \u2502 Median plants, with \u2502 (bilaterals). \u2502\n \u2502 prothallium: Mosses, ferns \u2502 \u2502\n \u2502 (muscin\u00e6 filicin\u00e6). \u2502 Metazoa with body cavity \u2502\n \u2502 \u2502 and anus (generally also \u2502\n \u2502 \u2502 blood\u2500vessels). Vermalia, \u2502\n \u2502 III. Anthophyta \u2502 mollusca, echinoderma, \u2502\n \u2502 (phanerogams). \u2502 articulata, tunicata, \u2502\n \u2502 \u2502 vertebrata. \u2502\n \u2502 Flowering plants, with \u2502 \u2502\n \u2502 blooms and seeds \u2502 \u2502\n \u2502 (spermophyta): \u2502 \u2502\n \u2502 Gymnosperms, angiosperms. \u2502 \u2502\n \u2502 \u2502 \u2502\n \u2502 \u2502 \u2502\n \u2502 \u2502 \u2502\n \u2502 \u2502 \u2502\n \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n\n\n\n\nIX\n\nMONERA\n\n The simplest forms of life--Cell theory and cell dogma--Precellular\n organisms: monera, cytodes, and cells--Actual monera--Chromacea\n (cyanophyce\u00e6)--Chromatophora--C\u0153nobia of chromacea: vital\n phenomena--Bacteria--Relations of the bacteria to the chromacea,\n the fungi, and the protozoa--Rhizomonera (protam\u0153ba, protogenes,\n protomyxa, bathybius)--Problematic monera--Phytomonera (plasmodoma)\n and zoomonera (plasmophaga)--Transition between the two classes.\n\n\nIn the study and explanation of all complex phenomena the first\nthing to do is to understand the simple parts, the manner of their\ncombination, and the development of the compound from the simple. This\nprinciple applies generally to inorganic objects, such as minerals,\nartificially constructed machines, etc. It is also of general\napplication in biological work. The efforts of comparative anatomy are\ndirected to the comprehension of the intricate structure of the higher\norganisms from the rising scale of organization and life in the lower,\nand the origin of the former by historical development from the latter.\nThe modern science of the cell (cytology), which has in a short time\nattained a considerable rank, pursues a method in opposition to this\nprinciple. The intricate composition of the unicellular organism, in\nmany of the higher protists (such as the ciliata and infusoria) and\nmany of the higher tissue-cells (such as the neurona) has led to the\nerroneous ascription of a highly complex organization to the cell in\ngeneral. One would be justified in saying that of late the cell-theory\nhas established itself in the dangerous and misleading position of a\ncell-dogma.\n\nThe modern treatment of the science, as we find it in numbers of recent\nworks, even in some of the most distinguished manuals, and which we\nmust resent on account of its dogmatism, culminates in something like\nthe following theses:\n\n1. The nucleated cell is the general elementary organism; all living\nthings are either unicellular, or made up of a number of cells and\ntissues.\n\n2. This elementary organism consists of at least two different organs\n(or, more correctly, organella), the internal nucleus and the outer\ncell-body (or cytoplasm).\n\n3. The matter in each of these cell-organs--the caryoplasm of the\nnucleus and the cytoplasm of the body--is never homogeneous (or\nconsisting of a chemical substratum), but always \"organized,\" or\nmade up of several chemically and anatomically different elementary\nconstituents.\n\n4. The plasm (or protoplasm) is, therefore, a morphological, not a\nchemical, unity.\n\n5. Every cell comes (and has come) only from a mother-cell, and every\nnucleus from a mother-nucleus (_omnis cellula e cellula--omnis nucleus\ne nucleo_).\n\nThese five theses of the modern cell-dogma are by no means sound; they\nare incompatible with the theory of evolution. I have, therefore,\nconsistently resisted them for thirty-eight years, and consider them\nto be so dangerous that I will briefly give my reasons. First, let\nus clearly understand the modern definition of the cell. It is now\ngenerally defined (in accordance with the second thesis) as being\ncomposed of two essentially different parts, the nucleus and the\ncell-body, and it is added that these organella differ constantly\nboth in respect of chemistry, morphology, and physiology. If that\nis really so, the cell cannot possibly be the primitive organism; if\nit were, we should have a miracle at the beginning of organic life\non the earth. The theory of natural evolution clearly and distinctly\ndemands that the cell (in this sense) is a secondary development from\na simpler, primary, elementary organism, a homogeneous cytode. There\nare still living to-day very simple protists which do not tally with\nthis definition, and which I designated _monera_ in 1866. As they must\nnecessarily have preceded the real cells, they may also be called\n\"precellular organisms.\"\n\nThe earliest organisms to live on the earth, with which the wonderful\ndrama of life began, can, in the present condition of biological\nscience, only be conceived as homogeneous particles of plasm--biogens\nor groups of biogens, in which there was not yet the division of\nnucleus and cell-body which characterizes the real cell. I gave the\nname \"cytodes\" to these unnucleated cells in 1866, and joined them\nwith the real nucleated cells under the general head of \"plastids.\"\nI also endeavored to prove that such cytodes still exist in the form\nof independent monera, and in 1870 I described in my _Monograph on\nthe Monera_ a number of protists which do not tally with the above\ndefinition.\n\nFifty years ago I made the first careful observations of living monera\n(_protam\u0153ba_ and _protogenes_), and described them in my _General\nMorphology_ (vol. i., pp. 133-5; vol. ii., p. xxii.) as structureless\norganisms without organs and the real beginnings of organic life.\nSoon afterwards, during a stay in the Canary Islands, I succeeded\nin following the continuous life-history of a related organism of\nthe rhizopod type, which behaved like a very simple mycetozoon, but\ndiffered in having no nucleus; I have reproduced the picture of it in\nthe first plate of my _History of Creation_. The description of this\norange-red globule of plasm (_protomyxa aurantiaca_) appeared first in\nmy _Monograph on the Monera_. Most of the organisms which I comprised\nunder this name exhibited the same movements as true rhizopods (or\nsarcodina). It was afterwards proved of some of them that there was\na nucleus hidden within the homogeneous particle of plasm, and that,\ntherefore, they must be regarded as real cells. But this discovery\nwas wrongly extended to the whole of the monera, and the existence of\nunnucleated organisms was denied altogether. Nevertheless, there are\nliving to-day several kinds of these organisms without organs, some\nof them being very widely distributed. The chief examples are the\nchromacea and the bacteria, the former with vegetal and the latter with\nanimal metabolism (or the former plasmodomous = plasma-forming, and the\nlatter plasmophagous = plasma-feeding). On the ground of this important\nchemical difference, I distinguished two principal groups of the monera\nin my _Systematic Phylogeny_ twenty years ago--the phytomonera and\nthe zoomonera, the former being unnucleated protophyta and the latter\nunnucleated protozoa.\n\nAmong living organisms the chromacea are certainly the most primitive\nand the nearest to the oldest inhabitants of the earth. Their simplest\nforms, the chroococcacea, are nothing but small structureless particles\nof plasm, growing by plasmodomism (formation of plasm) and multiplying\nby simple cleavage as soon as their growth passes a certain limit\nof individual size. Many of them are surrounded by a thin membrane\nor somewhat thicker gelatinous covering, and this circumstance had\nprevented me for some time from counting the chromacea as monera.\nHowever, I became convinced afterwards that the formation of a\nprotective cover of this kind around the homogeneous particle of\nplasm may indeed be regarded from the physiological stand-point as a\n\"purposive\" structure, but at the same time may be looked upon, from\nthe purely physical stand-point, as a result of superficial strain.\nOn the other hand, the physiological character of these plasmodomous\nmonera is especially important, as it gives us the simple key to the\nsolution of the great question of spontaneous generation (or archigony,\n_cf._ chapter xv.).\n\nThe chromacea are to-day found in every part of the earth, living\nsometimes in fresh water and sometimes in the sea. Many species form\nblue-green, violet, or reddish deposits on rocks, stones, wood, and\nother objects. In these thin gelatinous plates millions of small\nhomogeneous cytodes are packed close together. Their tint is due to a\npeculiar coloring matter (phycocyan), which is chemically connected\nwith the substance of the plasma-particle. The shade of this color\ndiffers a good deal in the various species of chromacea (of which more\nthan eight hundred have been distinguished); in the native species it\nis generally blue-green or sage-green, sometimes blue, cyanine blue,\nor violet. Hence the common name cyanophyce\u00e6 (_i.e._, blue alg\u00e6).\nIt is incorrect, for two reasons; firstly, because only a part of\nthese protophyta are blue, and, secondly, because they (as simple,\nprimitive plants without tissue) must be distinguished from the real\nalg\u00e6 (phyce\u00e6), which are multicellular, tissue-forming plants. Other\nchromacea are red, orange, or yellow in color, as the interesting\n_trichodesmium erythr\u00e6um_, for instance, the flaky masses of which,\ngathering in enormous quantities, cause at certain times the yellow\nor red coloring of the sea-water in the tropics; it is these that are\nresponsible for the name \"Red Sea\" on the Arabian and \"Yellow Sea\" on\nthe Chinese coast. When I passed the equator in the Sunda Straits on\nMarch 10, 1901, the boat sailed through colossal accumulations, several\nmiles in width, of this trichodesmium. The yellow or reddish surface of\nthe water looked as if it were strewn with sawdust. In the same way,\nthe surface of the Arctic Ocean is often colored brown or reddish-brown\nby masses of the brown _procytella primordialis_ (formerly described as\n_protococcus marinus_).\n\nIt is clearly quite illogical to regard the chromacea as a class\nor family of the alg\u00e6, as is still done in most manuals of botany.\nThe real alg\u00e6--excluding the unicellular diatomes and paulotomes,\nwhich belong to the protophyta--are multicellular plants that form\na _thallus_ or bed of a certain form and characteristic tissue. The\nchromacea, which have not advanced as far as the real nucleated cell,\nare unnucleated cytodes of a lower and earlier stage of plant-life.\nIf one would compare the chromacea with alg\u00e6 or other plants at all,\nthe comparison cannot be with their constituent cells, but merely\nwith the chromatophora or chromatella, which are found in all green\nplant-cells, and form _part_ of their contents. To be more precise,\nthese green granules of chlorophyll must be regarded as organella of\nthe plant-cell, or separated plasma-formations which arise beside the\nnucleus in the cytoplasm. In the embryonic cells of the germs of plants\nand in their vegetation points the chromatophora are as yet colorless,\nand are developed, as solid, very refractive, globular, or roundish\ngranules, from the firm layer of plasm which immediately surrounds the\nnucleus. Afterwards they are converted, by a chemical process, into\nthe green chlorophyll granules or chloroplasts, which have the most\nimportant function in the plasmodomism or carbon-assimilation of the\nplant.\n\nThe fact that the green chlorophyll granules grow independently\nwithin the living plant-cell and multiply by segmentation is very\nimportant and interesting. The globular chloroplasts are constricted\nin the middle, and split into two equal daughter-globules. These\ndaughter-plastids grow, and multiply in turn in the same way. Hence\nthey behave within the plant-cell just like the free-living chromacea\nin the water. On the strength of this significant comparison, one of\nour ablest and most open-minded scientists, Fritz M\u00fcller-Desterro, of\nBrazil, pointed out in 1893 that we may see in every green vegetal cell\na symbiosis between plasmodomous green and plasmophagous not-green\ncompanions (_cf._ my _Anthropogeny_, figs. 277 and 278, and in the\ntext).\n\nMany species of the simplest chromacea live as monobia (individually).\nWhen the tiny plasma globules have split into two equal halves by\nsimple segmentation, they separate, and live their lives apart. This\nis the case with the common, ubiquitous chroococcus. However, most\nspecies live in common, the plasma granules forming more or less thick\nc\u0153nobia, or communities or colonies of cells. In the simplest case\n(_aphanocapsa_) the social cytodes secrete a structureless gelatinous\nmass, in which numbers of blue-green plasma globules are irregularly\ndistributed. In the _gl\u0153ocapsa_, which forms a thin blue-green\ngelatinous deposit on damp walls and rocks, the constituent cytodes\ncover themselves immediately after cleavage with a fresh gelatinous\nenvelope, and these run together into large masses. But the majority\nof the chromacea form firm, threadlike cell communities or chains\nof plastids (catenal c\u0153nobia.) As the transverse cleavage of the\nrapidly multiplying cytodes always follows the same direction, and\nthe new daughter-cytodes remain joined at the cleavage surfaces, and\nare flattened into discoid shape, we get stringlike formations or\narticulated threads of considerable length, as in the oscillaria and\nnostochina. When a number of these threads are joined together in\ngelatinous masses, we often get large, irregular, jelly-like bodies, as\nin the common \"shooting-star jellies\" (_nostoc communis_). They attain\nthe size of a plum.\n\nIn view of the extreme importance which I attach to the chromacea as\nthe earliest and simplest of all organisms, it is necessary to put\nclearly the following facts with regard to their anatomic structure and\nphysiological activity:\n\n1. The organism of the simplest chromacea is _not_ composed of\ndifferent organella or organs; and it shows no trace of purposive\nconstruction or definite architecture.\n\n2. The homogeneous tinted plasma granule which makes up the entire\norganism in the simplest case (_chroococcus_) exhibits no plasma\nstructure (honeycomb, threads, etc.) whatever.\n\n3. The original globular form of the plasma particle is the simplest of\nall fundamental types, and is also that assumed by the inorganic body\n(such as a drop of rain) in a condition of stable equilibrium.\n\n4. The formation of a thin membrane at the surface of the structureless\nplasma granule may be explained as a purely physical process--that of\nsurface strain.\n\n5. The gelatinous envelope which is secreted by many of the chromacea\nis also formed by a simple physical (or chemical) process.\n\n6. The sole essential vital function that is common to all the\nchromacea is self-maintenance, and growth by means of their vegetal\nmetabolism, or plasmodomism (=carbon assimilation); this purely\nchemical process is on a level with the catalysis of inorganic\ncompounds (chapter x.).\n\n7. The growth of the cytodes, in virtue of their continuous\nplasmodomism, is on a level with the physical process of crystal growth.\n\n8. The reproduction of the chromacea by simple cleavage is merely the\ncontinuation of this simple growth process, when it passes the limit of\nindividual size.\n\n9. All the other vital phenomena which are to be seen in some of the\nchromacea can also be explained by physical or chemical causes on\nmechanical principles. Not a single fact compels us to assume a \"vital\nforce.\"\n\nEspecially noteworthy in regard to the physiological character of these\nlowest organisms are their bionomic peculiarities, especially the\nindifference to external influences, higher and lower temperatures,\netc. Many of the chromacea live in hot springs, with a temperature\nof fifty to eighty degrees centigrade, in which no other organism is\nfound. Other species may remain for a long time frozen in ice, and\nresume their vital activity as soon as it thaws. Many chromacea may be\ncompletely dried up, and then resume their life if put in water after\nseveral years.\n\nNext in order to the chromacea we have the bacteria, the remarkable\nlittle organisms which have been well known in the last few decades\nas the causes of fatal diseases, and the agents of fermentation,\nputrefaction, etc. The special science which is concerned with\nthem--modern bacteriology--has attained so important a position in\na short period--especially as regards practical and theoretical\nmedicine--that it is now represented by separate chairs at most of\nthe universities. We may admire the penetration and the perseverance\nwith which scientists have succeeded, with the aid of the best modern\nmicroscopes and methods of preparation and coloring, in making so\nclose a study of the organism of the bacteria, determining their\nphysiological properties, and explaining their great importance for\norganic life by careful experiments and methods of culture. The\nbionomic or economic position of the bacteria in nature's household\nhas thus secured for these tiny organisms the greatest scientific and\npractical interest.\n\nHowever, we find that certain general views have been maintained by\nspecialists in bacteriology up to our own time which are in curious\ncontrast with these brilliant results. The biologist who studies the\nsystematic relations of the bacteria from the modern point of view of\nthe theory of descent is bewildered at the extraordinary views as to\nthe place of the bacteria in the plant-world (as segmentation-fungi),\ntheir relations to other classes of plants, and the formation of their\nspecies. When we carefully consider the morphological properties that\nare common to all true bacteria and compare them with other organisms,\nwe are forced to the conclusion that I urged years ago in various\nwritings: the bacteria are not real (nucleated) cells, but unnucleated\ncytodes of the rank of the monera; they are not real (tissue-forming)\nfungi, but simple protists; their nearest relatives are the chromacea.\n\nThe individual organisms of the simplest kind, which bacteriologists\ncall \"bacteria-cells,\" are not real nucleated cells. That is the clear\nnegative result of a number of most careful investigations which\nhave been made up to date with the object of finding a nucleus in\nthe plasma-body of the bacteria. Among recent exact investigations\nwe must especially note those of the botanist Reinke, of Kiel, who\nsought in vain to detect a nucleus in one of the largest and most\neasily studied genera of the bacteria, the _beggiatoa_, using every\nmodern technical aid. His conviction that this important cell-structure\nis really lacking is the more valuable, as it is very prejudicial\nto his own theory of \"dominants.\" Other scientists (especially\nSchaudinn) have recently claimed, as equivalent to a nucleus in some\nof the larger bacteria, a number of very small granules, which are\nirregularly distributed in the plasm, and are strongly tinted under\ncertain coloring processes. But even if the chemical identity of these\nsubstances which take the same color were proved--which is certainly\nnot the case--and even if the appearance of scattered nuclein-granules\nin the plasm could be regarded as a preliminary to, or a beginning\nof, the differentiation of an individual, morphologically distinct\nnucleus, we should not yet have shown its independence as an organellum\nof the cell.\n\nNor is this any more proved from the circumstance that in some bacteria\n(not all) we find a severance of the plasm into an inner and outer\nlayer, or a frothy structure with vacuole-formation, or a special\nsharply outlined membrane on the plastid. Many bacteria (but not all)\nhave such a membrane, like the nearly related chromacea, and also the\nsecretion of a gelatine envelope. Both classes have also in common\nan exclusively monogenetic reproduction. The bacteria multiply, like\nthe chromacea, by simple segmentation; as soon as the structureless\nplasma-granule has reached a certain size by simple growth, it is\nconstricted and splits into two halves. In the long-bodied bacteria\n(the rod-shaped bacilli) the constriction always goes through the\nmiddle of the long axis, and is, therefore, simple transverse cleavage.\nMany bacteria have also been said to multiply by the formation of\nspores. But these so-called \"spores\" are really permanent quiescent\nforms (without any multiplication of individuals); the central part\nof the plastid (endoplasm) condenses, separates from the peripheral\npart (exoplasm), and undergoes a chemical change which makes it very\nindifferent to external influences (such as a high temperature).\n\nThe great majority of the bacteria differ so little morphologically\nfrom the chromacea that we can only distinguish these two classes\nof monera by the difference in their metabolism. The chromacea,\nas protophyta, are plasmodomous. They form new plasm by synthesis\nand reduction from simple inorganic compounds--water, carbonic\nacid, ammonia, nitric acid, etc. But the bacteria, as protozoa, are\nplasmophagous. They cannot, as a rule, form new plasm, but have to\ntake it from other organisms (as parasites, saprophytes, etc.);\nthey decompose it by analysis and oxydation. Hence the colorless\nbacteria are without the important green, blue, or red coloring matter\n(phycocyan) which tints the plastids of the chromacea, and is the real\ninstrument of the carbon-assimilation. However, there are exceptions\nin this respect: _bacillus virens_ is tinted green with chlorophyll,\n_micrococcus prodigiosus_ is blood-red, other bacteria purple, and\nso on. Certain earth-dwelling bacteria (_nitro-bacteria_) have the\nvegetal property of plasmodomism; they convert ammonia by oxydation\ninto nitrous acid, and this into nitric acid, using as their source of\ncarbon the carbonic acid gas in the atmosphere. They are thus quite\nindependent of organic substances, and feed, like the chromacea, on\nsimple inorganic compounds.\n\nHence the affinity between the plasmodomous chromacea and plasmophagous\nbacteria is so close that it is impossible to give a single safe\ncriterion that will effectually separate the two classes. Many\nbotanists accordingly combine both groups in a single class with the\nname of _schizophyta_, and within this distinguish as \"orders\" the\nblue-green chromacea as _schizophyc\u00e6_ (cleavage-alg\u00e6) and the colorless\nbacteria as _schizomycetes_ (cleavage-fungi). However, we must not\ntake this division too rigidly; and the absolute lack of a nucleus\nand tissue-formation separates the chromacea just as widely from the\nmulticellular tissue-forming alg\u00e6 as the bacteria from the fungi. The\nsimple multiplication by the halving of the cell, which is expressed in\nthe name \"cleavage-plants\" (_schizophyta_), is also found in many other\nprotists.\n\nThe number of forms that can be distinguished as species in the\ntechnical sense is very great in the case of the bacteria, in\nspite of the extreme simplicity of their outward appearance; many\nbiologists speak of several hundred, and even of more than a thousand,\nspecies. But when we look solely to the outer form of the living\nplasma-granule, we can only distinguish three fundamental types: (1)\nMicrococci, or spherobacteria (briefly, cocci), globular or ellipsoid;\n(2) bacilli, or rhabdo-bacteria (also called eubacteria, or bacteria in\nthe narrower sense), rod-shaped, cylindrical, and often twisted like\nworms (comma-bacilli); (3) spirilla, or spirobacteria, screw-shaped\nrods (vibriones when the screw is slight, and spiroch\u00e6ta when it\nhas many coils). Besides this threefold difference in the forms of\nthe cytodes, we have a ground of distinction in many bacilli and\nspirilla in the possession of one or more very thin lashes (flagella),\nwhich proceed from one of both poles of the lengthened plastid. The\nconstruction and vibration of these serves for locomotion in the\nswimming bacteria; but they are only found for a time in many species,\nand in many others are altogether wanting.\n\nSince, then, neither the simple outer form of the bacterium-cytodes\nnor their homogeneous internal structure provides a satisfactory\nground for the systematic distinction of the numerous species,\ntheir physiological properties are generally used for the purpose,\nespecially their different behavior towards organic foods (albumin,\ngelatine, etc.), their chemical actions, and the various effects of\npoisoning and decomposition which they produce in the living organism.\nNo bacteriologist now doubts that all the vital activities of the\nbacteria are of a chemical nature, and precisely on this account\nthese microbes are of extreme importance. When we bear in mind how\ncomplicated are the relations of the various species of bacteria to\nthe tissues of the human body, in which they cause the diseases of\ntyphus, hypochondriasis, cholera, and tuberculosis, we are bound to\nadmit that the real cause of these maladies must be sought in the\npeculiar molecular structure of the bacterium-plasm, or the particular\narrangement of its molecules and the innumerable atoms (more than a\nthousand) which are, in a very loose way, made up into special groups\nof molecules. The chemical products of their mutual action are what we\ncall ptomaines, which are partly very virulent poisons (toxins). We\nhave succeeded in producing several of these poisonous matters in large\nquantities by artificial culture, and isolating them and experimentally\nascertaining their nature; as, for instance, tetanin, which causes\ntetanus, typhotoxin, the poison of typhus, etc.\n\nIn thus declaring the action of bacteria to be purely chemical and\nanalogous to that of well-known inorganic poisons, I would particularly\npoint out that this very justifiable statement is a pure hypothesis;\nit is an excellent illustration of the fact that we cannot get on\nin the explanation of the most important natural phenomena without\nhypotheses. We can see nothing whatever of the chemical molecular\nstructure of the plasm, even under the highest power of the microscope;\nit lies far below the limit of microscopic perception. Nevertheless,\nno expert scientist has the slightest doubt of its existence, or that\nthe complicated movements of the sensitive atoms and the molecules and\ngroups of molecules they make up are the causes of the vast changes\nwhich these tiny organisms effect in the tissues of the human and the\nhigher animal body.\n\nMoreover, the distinction of the many species of bacteria is of\ninterest in connection with the general question of the nature and\nconstancy of a species. Whereas formerly in biological classification\nonly definite morphological characters, or definable differences in\nouter form or inner structure, were regarded as of any moment in the\ndistinction of species, here, in view of the vagueness or total lack\nof these characters, we have to look mainly to the physiological\nproperties, and these are based on the chemical differences in their\nhypothetical molecular structure. But even these are not absolutely\nconstant; on the contrary, many bacteria lose their specific qualities\nby progressive culture under changed food-conditions. By a change in\nthe temperature and the nutritive field in which a number of poisonous\nbacteria have been reared, or by the action of certain chemicals, not\nonly the growth and multiplication are altered, but also the injurious\neffect they have on other organisms by the generation of poisons.\nThis poisonous effect is weakened, and--what is most important--the\nweakening is transmitted by heredity to the following generations. On\nthis is based the familiar process of inoculation, an admirable example\nof the inheritance of acquired characteristics.\n\nAs the bacteria are still often described as \"cleavage-fungi\" and\nclassified along with the real fungi, we must particularly point\nout the wide gulf that separates the two groups. The real fungi (or\n_mycetes_) are metaphyta, their multicellular body (_thallus_) forming\na very characteristic sort of tissue, the mycelium; this is composed\nof a number of interlaced and interwoven threads (or hyphens). Each\nfungus-thread consists of a row of lengthened cells, which have a thin\nmembrane and enclose a number of small nuclei in the colorless plasm.\nMoreover, the two sub-classes of the real fungi, the ascomycetes and\nbasimycetes, form peculiar fruit-bodies which generate spores (ascodia\nand basidia). There is no trace whatever of these real characteristics\nof the true fungus in the bacteria. Nor is it less incorrect to class\nthem with the fungilli, the so-called unicellular fungi or phycomycetes\n(ovomycetes and zygomycetes); these form a special class of protists\nwhich has the closest affinity to the gregarin\u00e6.\n\nLike the closely related chromacea, many of the bacteria show a marked\ntendency to form communities or cell-colonies. These cell-communities\narise, as elsewhere, from the fact that the individuals, which\nmultiply rapidly by continuous cleavage, remain joined together.\nThis may happen in two ways. When the social bacteria secrete large\nquantities of gelatine, and remain distributed in this, we have the\n_zoogl\u0153a_ (as in the case of the _aphanocapsa_ and _gl\u0153ocapsa_\namong the chromacea). If, on the other hand, the long-bodied\nbacilli remain fastened together in rows, we get the knotted\nthreads of _leptothrix_ and _beggiatoa_ (which may be compared with\nthe oscillaria). And, if these threads go into branches, we have\n_cladothrix_. Other c\u0153nobia of bacteria have the appearance of\ndisks, the cytodes dividing in a plane, usually in groups of four (as\nin _merismopedia_), or of cube-shaped packets when they are in all\nthree directions of space (_sarcina_).\n\nThe two classes of bacteria and chromacea seem, in the present\ncondition of our knowledge, on account of their simple organization,\nto be the simplest of all living things, real monera, or organisms\nwithout organs. Hence we have to put them at the lowest stage of\nthe protist kingdom, and must regard the difference between them\nand the most highly differentiated unicellular beings (such as the\nradiolaria, ciliated infusoria, diatomes, or siphonea) as no smaller\nthan the difference (in the realm of the histona) between a lower\npolyp (_hydra_) and a vertebrate, or between a simple alga (_ulva_)\nand a palm. But if the kingdom of the protists is badly divided, on\nthe older rule, into a plant kingdom and an animal kingdom, the only\ndiscriminating mark we have left is the difference in metabolism; in\nthat case we have to include the plasmophagous bacteria in the animal\nkingdom (as Ehrenberg did in 1838) and the plasmodomous chromacea\nin the plant kingdom. The remarkable class of the flagellata, which\nincludes ciliated unicellulars of both groups, contains several\nforms which are only distinguished from the typical bacterium by the\npossession of a nucleus. If it is true that in some of the protists\nwhich were counted as bacteria a real nucleus has been detected, these\nmust be separated from the others (unnucleated) and included in the\nnucleated flagellata.\n\nThe monera which I described in 1866, and on which I based the theory\nof the monera in my monograph, belong to a different division of the\nprotists from the classes of bacteria and chromacea. These are the\nforms which I described as _protam\u0153ba_, _protogenes_, _protomyxa_,\netc. Their naked mobile plasma-bodies thrust out pseudopodia, or\nvariable \"false feet,\" from their surface, like the (nucleated) real\nrhizopods (=sarcodin\u00e6); but they differ essentially from the latter in\nthe absence of a nucleus. Afterwards (in my _Systematic Phytogeny_)\nI proposed to separate these unnucleated rhizopods from the others,\ngiving the name of _lobomonera_ (_protam\u0153ba_) to the am\u0153ba-like\nmonera with flap-shaped feet, and the name of _rhizomonera_\n(_protomyxa_, _pontomyxa_, _biomyxa_, _arachnula_, etc.) to the\ngromia-like, root-feet forming monera. However, of late years, real\nnuclei have been detected in each of these large monera, and so they\nhave been proved to be true cells. This discovery was made possible by\nthe improved modern methods of coloring the nucleus which I had not the\nuse of thirty years ago in my first observations. On the strength of\nthese recent discoveries many scientists claim that all the monera I\ndescribed are true cells, and must have nuclei. This baseless assertion\nis much employed by the opponents of the theory of evolution in order\nto deny the existence of the monera altogether.\n\nOf the genus of monera which we call protam\u0153ba I have given an\nillustration in my _History of Creation_ (tenth edition), which has\nbeen frequently reproduced. Several species (at least two or three)\nof this genus still exist, and are distinguished by the shape of\ntheir flap-formation and their method of motion. They resemble\nordinary simple am\u0153b\u00e6, and only differ from these to any extent\nin the absence of a nucleus. The _protam\u0153ba primitiva_ seems\nto be pretty widely distributed; it has been found repeatedly by\nobservers (Gruber, Cienkowski, Leidy, etc.) in inland waters. In the\nzoological demonstrations which I have given at the University of Jena\nfor forty years, and in the course of which the lowly inhabitants\nof our fresh water are regularly examined with the microscope, the\n_protam\u0153ba primitiva_ has been found four or five times. It\nalways had the same form, as I described it, moved about by the slow\nformation of flaps at its surface, multiplied by simple cleavage,\nand showed no trace of a nucleus in its homogeneous plasma-body even\nwith the most careful application of the modern methods of tinting\nthe nucleus. A larger number of very fine granules (microsoma) that\nwere irregularly distributed in the plasm, and were more or less\ncolored by nucleus-reagents, cannot be reckoned as clear equivalents\nof the nucleus in this or in similar cases; they are probably products\nof metabolism. The same may be said of the larger marine form of\nrhizomoneron, which A. Gruber has recently called _pelomyxa pallida_.\n\nThe large marine form of rhizomoneron to which Huxley gave the name\nof _bathybius Haeckelii_ in 1868, and as to the real nature of which\nmany opinions have been expressed, seems, according to the latest\ninvestigation, not to have the significance ascribed to it. However,\nthe much-discussed question of the bathybius is superfluous as far as\nour monera theory and the associated hypothesis of archigony (chapter\nxv.) are concerned, since we have now a better knowledge of the much\nmore important monera-forms of the chromacea and bacteria.\n\nIn the case of some of the protists I described in my _Monograph on the\nMonera_, it is at present doubtful whether their plasma-body contains\na nucleus or not, and, therefore, whether they are to be classed as\ntrue cells or cytodes. This applies especially to the forms which\nonly happened to come under observation once, such as _protomyxa_\nand _myxastrum_. In these obscure cases we must wait for fresh\ninvestigations and the application of the modern methods of tinting\nthe nucleus. I may, however, point out, in passing, that these famous\nmethods of nucleus-coloring give by no means the absolute certainty\nwhich is ascribed to them; there are other substances which take color\nin the same way as chromatin. As far as my monera theory is concerned,\nor the great general importance which I attach to these unnucleated\nliving granules of plasm, it does not matter whether a nucleus is\ndetected in these problematic monera or not. The chromacea alone--the\nmost important of all monera--completely suffice to provide a base for\nthe far-reaching theoretical conclusions which I draw from it.\n\nAt the close of these observations on the monera I will briefly\nrecapitulate the weighty inferences which we can deduce from their\nsimple organization. They serve as a solid foundation for the chief\ntheses of our monistic biology; and they are inconsistent with the\ndualistic views of modern vitalists. In the first place, I emphasize\nthe fact that the structureless plasm-body of the simple monera has\nno sort of organization and no composition from dissimilar parts\nco-operating for definite vital aims. Reinke's conscious \"dominant\"--as\nwell as Weismann's mechanical \"determinants\"--have nothing to do here.\nThe whole vital activity of the simplest monera, especially of the\nchromacea, is confined to their metabolism, and is therefore a purely\nchemical process, that may be compared to the catalysis of inorganic\ncompounds. The simple formation of individuals in this primitive living\nmatter is merely a question of the cleavage of plasma globules of a\ncertain size (_chroococcus_); and their primitive multiplication (by\nsimple self-division) is only a continued growth (analogous to that\nof the crystal). When this simple growth passes a certain limit, that\nis fixed by the chemical constitution, it leads to the independent\nexistence of the redundant growth-products.\n\n\n\n\nX\n\nNUTRITION\n\n Functions of nutrition--Assimilation and disassimilation--Plasmodoma\n and plasmophaga--Phytoplasm and zooplasm--Plasmodomism of\n plants--Chlorophyll granules and nitro-bacteria--Plasmophagism of\n fungi and animals--Metasitism (conversion of metabolism)--Nutrition\n of the monera (chromacea, bacteria, rhizomonera)--Nutrition of the\n protophyta and metaphyta (cell-plants and tissue-plants)--Nutrition\n of the metazoa--- Gastr\u00e6a theory--Gastro-canal system of the\n c\u0153lenteria (gastr\u00e6ads, sponges, cnidaria, platodes)--Nutrition\n of the c\u0153lomaria (digestion, circulation, respiration,\n evacuation)--Saprositism--Parasitism--Symbiosis.\n\n\nThe wonder of life which we call, in the widest sense of the word,\n\"nutrition\" is the chief factor in the self-maintenance of the organic\nindividual. It is always bound up with a chemical modification of the\nliving matter, an organic metabolism (circulation of matter), and a\ncorresponding circulation of force. In this chemical process plasm is\nused up, built up afresh, and once more disintegrated. The metabolism\nwhich lies at the root of this chemistry of food is the essential\nfeature in the manifold processes of nutrition. A large part of the\nseveral nutritive processes are explained without further trouble\nby the known physical and chemical properties of inorganic bodies;\nfor another part of them we have not yet succeeded in doing this.\nNevertheless, all impartial physiologists now agree that it is possible\nin principle, and that we have no reason to introduce a special vital\nprinciple. All the trophic (nutritive) processes, without exception,\nare subject to the law of substance.\n\nIn all the higher plants and animals the chemical process of\nmetabolism, with the stream of energy that accompanies it, is a very\ncomplex vital activity, in which many different functions and organs\nco-operate with the common aim of self-maintenance. As a rule, they are\ndistributed in four groups--namely: (1) Intussusception of food and\ndigestion: (2) distribution of the food in the body, or circulation;\n(3) respiration, or exchange of gases; and (4) excretion of unusable\nmatter. In most of the histona, either tissue-plants or tissue-animals,\na number of organs are differentiated for the accomplishment of these\ntasks. At the lower stages of life this division of labor is not found,\nthe entire process of nutrition being accomplished by a single layer of\ncells (lower alg\u00e6, gastr\u00e6ads, sponges, lower polyps). In the protists,\nagain, it is the single cell that does all these things itself; in the\nsimplest cases, the monera, a homogeneous plasma-globule. As a long\ngradation uninterruptedly unites these lowest forms of nutrition with\nthe more complicated forms, we must regard the latter no less than the\nformer as physico-chemical processes.\n\nWhen we take the whole of the metabolic functions in organisms\ntogether, we may look upon them as the outcome of two opposite chemical\nprocesses--on the one hand the building-up of living matter by taking\nin food (assimilation), and on the other the breaking-down of it in\nconsequence of its vital activity (disassimilation). As in every case\nthe plasm is the active living matter, we may say: _Assimilation_ (or\nplasma-production) consists in the conversion within the organism into\nthe special plasm of the particular species of food that has been\nreceived from without; _disassimilation_ (or plasma-destruction)\nis the result of the work done by the plasm, which is the cause of\nits partial decomposition or breakdown. In both respects there is a\nstriking difference between the two great kingdoms of organic nature.\nThe plant kingdom is, on the whole, the agent of assimilation, forming\nnew plasm by synthesis and reduction from inorganic matter. In the\nanimal world, on the contrary, disassimilation preponderates, the plasm\nreceived being resolved by oxydation, and the actual energy taken out\nof it by analysis being converted into heat and motion. Plants are\nplasmodomous; animals, plasmophagous.\n\nOf all the chemical processes the most important, because the most\nindispensable, for the origin and maintenance of organic life is the\nconstant reconstruction of plasm. We give it the name of plasmodomism\n(_domeo_=to build up), or carbon-assimilation. Botanists have the\nhabit of late of calling it briefly assimilation, and have thus\ncaused a good deal of misunderstanding. The more common and older\nmeaning of assimilation in animal physiology is, in the widest sense,\nthe intussusception and preparation of the food received. But the\ncarbon-assimilation in plants--what I call plasmodomism--is only the\nfirst and original form of plasma-production. It means that the plant\nis able, under the influence of sunlight, to form carbohydrates,\nand from these new plasm, out of simple inorganic compounds (water,\ncarbonic acid, nitric acid, and ammonia) by synthesis and reduction.\nThe animal is unable to do this. It has to take its plasm in its\nfood from other organisms--plant-eaters directly, and animal-eaters\nindirectly. We therefore give the title of _plasmophagous_ to these\nanimal \"plasma-eaters.\" In working up the foreign plasm it has eaten,\nand converting it into its own specific form of plasm, the animal\nalso accomplishes assimilation; but this animal albumin-assimilation\nis totally different from the vegetal carbon-assimilation. The\nfresh-formed animal plasm is then broken up by oxydation, and by this\nanalysis the energy needed for the vital movements is obtained.\n\nThe physiological contrast which we thus find between the two principal\nforms of living matter, the synthetic plasm of the plant and the\nanalytic plasm of the animal, is of great importance for the lasting\nmaintenance of the whole organic world. It depends on a reversal of\nthe molecular movement in the plasm, the intimate nature of which is\njust as little known to us as the chemical constitution of the albumins\nin general, and that of living albumin, the plasm, in particular. As\nI mentioned in chapter v., modern physiological chemistry has good\nreason to believe that the invisible albumin-molecule is, comparatively\nspeaking, gigantic, and is composed of more than a thousand atoms.\nThese are in such an unstable equilibrium, so complicated and\nimpermanent an arrangement, that the slightest push or stimulus\nsuffices to alter them and form a new kind of plasm. As a fact, the\nnumber and variety of kinds of plasm are immense. This is seen at\nonce from the ontogenetic fact that the ovum and sperm-cell of each\nspecies (and each variety) have a specific chemical constitution.\nIn reproduction this is transmitted to the offspring. But, setting\naside these countless finer modifications, we may distinguish two\nchief groups of kinds of plasm: the phytoplasm of the plant, with the\nsynthetic property of plasmodomism, and the zooplasm of the animal,\nwhich is destitute of this property, and so confined to plasmophagy.\n\nThe remarkable synthetic process of building up the plasm, to which\nwe give the name of plasmodomism, or carbon-assimilation, usually\nneeds as its first condition the radiant energy of sunlight. Every\ngreen plant-cell contains in its chlorophyll-granules so many tiny\nlaboratories, their green plasm being able to form new plasm out of\ninorganic compounds under the influence of light. The water that is\nneeded for this, besides nitrogenous compounds (nitric acid, ammonia),\nis drawn from the earth by the roots; the carbonic acid is taken from\nthe atmosphere by the green leaves. The immediate products of the\nsynthesis, due to the separation of the carbonic acid, is, as a rule, a\nnon-nitrogenous starch-flour (_amylum_). This is further used for the\ncomposition of the nitrogenous albumin by an as yet unknown synthetic\nprocess, with the aid of nitrogenous mineral compounds. In this process\nof reduction the separated free oxygen is returned to the atmosphere.\nThe carbohydrates that chiefly co-operate in this are glucoses and\nmaltoses: the mineral substances, especially salts of potassium and\nmagnesium, and compounds of these elements with nitric acid, sulphuric\nacid, and phosphoric acid. Iron is also found to be an important\nelement in the process, though in a very small quantity. As a rule,\nthe ferruginous chlorophyll can only form new plasm with the help of\nlight-waves. The most important part of the spectrum for this purpose\nis that containing the red, orange, and yellow waves.\n\nThe chief factor in plasma-formation in the organic world is the\nphotosynthesis, or ordinary carbon-assimilation by chlorophyll, the\nwonderful green matter that amounts to only a very small percentage\n(about one-tenth) of the weight of the chlorophyll-granules, and can\nbe separated from their plasmatic substance by certain methods. Even\nwhen the plant has some other color than green the chlorophyll is still\nthe real plasmodomous substance. Its green color is then masked by\nsome other color--diatomin in the yellow diatomes, phycorhodin in the\nred rhodophyce\u00e6, phycoph\u00e6in in the brown ph\u00e6ophyce\u00e6, and phyocyan in\nthe blue-green chromacea or cyanophyce\u00e6. The latter have an especial\ninterest for us, because in the simplest specimens the entire organism\nis merely a globular bluish-green granule of plasm. Moreover, in the\nsimplest forms of nucleated primitive plants (_algari\u00e6_)--many of the\nso-called unicellular alg\u00e6--the metabolism is effected by a single\ngrain of chlorophyll. There is usually a large number of them in the\nplasm of the plant-cells.\n\nAnother kind of plasm-synthesis, quite different from the ordinary\nplasmodomism by chlorophyll and sunlight has lately been discovered in\nsome of the lowest organisms (by Heraeus, Winogradsky, and others). The\nnitro-bacteria (or nitromonades) are tiny monera (unnucleated cells)\nthat live in complete darkness underground. Their globular colorless\nplasma-bodies contain neither chlorophyll nor nucleus. They have the\nremarkable capacity of forming carbohydrates, and from these plasm,\nby a peculiar synthesis out of purely inorganic compounds--water,\ncarbonic acid, ammonia, and nitric acid. Pfeffer has called this\ncarbon-assimilation, on account of its purely chemical nature,\n\"chemosynthesis,\" in opposition to the ordinary photosynthesis by\nmeans of sunlight. There are also other bacteria (sulphur-bacteria,\npurple-bacteria, etc.) that show various peculiarities of metabolism.\nThe nitro-bacteria must belong to the oldest monera, and represent a\ntransition from the vegetal chromacea to the animal bacteria.\n\nThe extensive class of the fungi (or _mycetes_) resembles a part of\nthe bacteria in regard to metabolism. These organisms are, it is true,\ngenerally regarded as plants, but they have not the capacity of the\ngreen, chlorophyll-bearing plants to supply themselves with carbon\nfrom the carbonic acid in the atmosphere. They have to take it from\norganic substances, such as albumin, carbohydrates, etc., like the\nanimals. But while the animals have to derive their nitrogen from the\nlatter, the fungi can obtain it from inorganic matter in the earth.\nFungi cannot support life without the addition of organic compounds;\nbut we can make them grow in a food solution consisting of sugar and\npurely inorganic nitrogenous salts. Thus they are on the border that\nseparates the plasmodomous plants from the plasmophagous animals. Like\nthe latter, the fungi have evolved from the plants through changed food\nconditions. We find this process even among the unicellular protists in\nthe phycomycetes, which descend from the siphonea. In the same way the\nreal multicellular fungi (ascomycetes and basimycetes) may be traced to\nthe tissue-forming alg\u00e6.\n\nAll true animals have to derive their food from the plant kingdom, the\nvegetal feeders directly, and the flesh feeders indirectly, when they\nconsume vegetal feeders. Hence the animals are, in a certain sense, as\nthe older natural philosophy put it four hundred years ago, \"parasites\nof the plant world.\" From the point of view of phylogeny, the animal\nkingdom is, therefore, clearly much younger than the plant kingdom. The\ndevelopment of the animals from the plants was determined originally by\na change in the method of nutrition which we call metasitism.\n\nThe chemical modification of the living matter which is connected\nwith the loss of plasmodomism--in other words, the conversion of the\nreducing phytoplasm into oxidizing zooplasm--must be regarded as\none of the most important changes in the history of organic life.\nThis \"reversal of metabolism\" is polyphyletic; it has been repeated\nmany times in the course of biological history, and has taken place\nindependently in very different groups of the organic world--whenever\na plasmodomous cell or group of cells (=tissue) had occasion to feed\ndirectly on ready-made plasm, instead of giving itself the trouble of\nbuilding it up out of inorganic compounds. We see this particularly\namong the unicellular protists in the independent ciliated cells.\nThe longer plasmophagous flagellata, which are colorless, and have\nno chlorophyll (monodina, conoflagellata), closely resemble in\nform and movement the older plasmadomous and chlorophyll-bearing\nmastigota, from which they are descended (volvocina, peridinia); they\nonly differ in the manner of nutrition. The colorless flagellata\nfeed on ready-formed plasm, which they obtain either by means of\ntheir lashes or by a special cell mouth in their cell body. On the\nother hand, their ancestors, the green or yellow mastigota, form\nnew plasm by photosynthesis like true cells. But there are also\ncomplete intermediate forms between the two groups--for instance, the\nchrysomonades and the gymnodinia; these may behave alternately as\nprotozoa or protophyta. In the same way we can derive the phycomycetes\nby metasitism from the siphonea, the fungi from the alg\u00e6; and, finally,\nthe process is also found in many of the higher parasitic plants\n(orchids, orobanches, etc.). (See under \"Parasitism.\")\n\nAs is the case with every other vital function, so for the function\nof metabolism we find a starting-point in the lowest and simplest\ngroup of the protophyta, the chromacea. In their oldest forms, the\nchroococcacea, the whole body is merely a blue-green, structureless,\nglobular plasma particle, growing by means of its plasmodomous power,\nand splitting up as soon as it reaches a certain stage of growth.\nThere the miracle of life consists merely of the chemical process of\nplasmodomism by photosynthesis. The sunlight enables the blue-green\nphytoplasm to form new plasm of the same kind out of inorganic\ncompounds (water, carbonic acid, ammonia, and nitric acid). We may look\nupon this process as a special kind of catalysis. In this case there\nis absolutely nothing to be done by Reinke's \"dominants,\" or conscious\nand purposive vital forces. There are, as yet, no differentiated\nphysiological functions in these organisms without organs, and no\nanatomically distinct members; and so their one vital activity, growth,\nmay very well be compared to the simple growth of inorganic crystals.\n\nIt has been pointed out repeatedly that the remarkable monera which\nnow play so important a part in biology as bacteria stand, in many\nrespects, quite apart from the ordinary vital phenomena of the\nhigher organisms. This is especially true of their metabolism, which\nhas the most striking peculiarities. Morphologically, many of the\nbacteria cannot be distinguished from their nearest relatives and\ndirect ancestors, the chromacea, differing from them only in the\nabsence of coloring matter in the plasm. Many of them are simple,\nglobular, ellipsoid, or rod-shaped plasma particles, without any\nvisible organization or movement. Others move about by means of one or\nmore very fine lashes (like the flagellata). No real nucleus can be\ndiscovered in the structureless plasma body. The very fine granules\nwhich are found in some species, and the vacuole-formation that we see\nin others, may be regarded as products of metabolism; and the same\nmay be said of the thin membrane or the thicker gelatinous envelope\nwhich many of the bacteria secrete. This makes all the more remarkable\nthe peculiarity of their chemical constitution and the metabolism\ndetermined thereby. The nitro-bacteria we have mentioned previously are\nplasmodomous; the ana\u00ebrobe bacteria (of butyric acid and tetanus) only\nflourish where oxygen is excluded; the sulphur bacteria (_beggiatoa_)\nsecrete--by the oxydation of sulphuretted hydrogen--pure regulation\nsulphur in the form of round granules. The ferruginous bacteria\n(_leptothrix ochrocea_) store up oxyhydrate of iron (by the oxydation\nof carbonic protoxide of iron). The saprogenetic bacteria cause\nputrefaction, and the zymogenetic fermentation. Finally, we have the\nvery interesting pathogenetic bacteria which cause the most dangerous\ndiseases by the secretion of special poisons--toxins--festering,\nsmall-pox, tetanus, diphtheria, typhus, tuberculosis, cholera, etc.\nOn account of their great practical importance, these bacteria have\nof late been taken over by a special branch of biology, bacteriology.\nBut only a few of the many experts in this department have pointed out\nthe extreme theoretical significance which these zoomonera have for\nthe important questions of general biology. These structureless plasma\nbodies show unmistakably that their vital activity is a purely chemical\nphenomenon. Their great variety proves how manifold and complicated\nmust be the molecular composition of the plasm, even in these simplest\norganisms.\n\nThe unicellular protophyta exhibit the same form of metabolism and\nplasmodomism as the familiar green cells of the tissue-plants; but\nin most of the protozoa we find special features of nutrition and\nplasmophagy. The great class of the rhizopods is distinguished by the\nfact that their naked plasma body can take in ready-formed solid food\nat any point of its surface. On the other hand, most of the infusoria\nhave a definite mouth-opening in the outer wall of their unicellular\nbody, and sometimes a gullet-tube as well. Besides this cell-mouth\n(_cytostoma_) we usually find also a second opening for the discharge\nof indigestible matter, a cell-anus (_cytopyge_).\n\nMetabolism in the tissue plants (metaphyta) forms a long gradation from\nvery simple to very complicated arrangements. The lowest and oldest\nthallophyta, especially the simplest alg\u00e6, are not far removed from\nthe communities of protophyta, and, like these, are merely definitely\ngrouped colonies of cells. The social cells which form their most\nrudimentary tissue are quite homogeneous, with no differentiation\nbeyond that of sex. The thallus or bed-formation consists in the\nsimplest specimens of plain or branched fine threads, consisting of\nrows or chains of homogeneous cells (so _conferva_ among the green,\n_ectocarpus_ among the brown, and _callithamnion_ among the red\nalg\u00e6). Other alg\u00e6 (such as the ulva) form thin leaf-shaped forms of\nthe thallus, a number of homogeneous cells lying side by side along a\nlevel. In the larger alg\u00e6 compact tissue-bodies are formed, in which\nfrequently firmer rows of cells exhibit the rudiments of fibres; and\nthe thallus divides, as in the cormophyta, into root, stalk, and\nleaves. There is also a trophic differentiation, the fibres undertaking\nspecial functions of nutrition (the conduction of the sap). The\nsame must be said of the mosses (_bryophyta_). Their lowest forms\n(_ricciadin\u00e6_) are close akin to the alg\u00e6; the highest mosses (the\n_mnium_ and _polytrichum_, for instance) approach the cormophyta. Many\nbotanists comprise these lower plants--alg\u00e6, fungi, and mosses--under\nthe title of \"cell-plants\" (_cytophyta_), and oppose the higher\nplants--ferns and flowering-plants--to them as \"vascular plants\"\n(_angiophyta_), because they have complex fibres or sap vessels. This\ndistinction has a phylogenetic significance similar to the division\nbetween c\u0153lenteria and c\u0153lomaria in the animal kingdom.\n\nWhile most of the cell-plants either live in the water (alg\u00e6) or are\nvery simply organized on account of their saprophytic or parasitic\nhabits (fungi), the vascular plants mostly live on land, and have to\nadapt themselves to much more complicated conditions. Their nutrition\nis accordingly distributed among different functions, and special\norgans have been evolved to discharge them. This is equally true of\nthe crytogam ferns (_pteridophyta_) and the phanerogam flowering\nplants (_anthophyta_). The most important later acquisition which\ndistinguishes both groups from the lower cell-plants is the possession\nof vascular or conducting fibres. These organs for conducting water\npass through the entire body of the vascular plant in the shape of\nlong tubes, formed by the combination of rows of cells; the cells\nthemselves die off, and their plasma content disappears. The stream of\nwater that rises constantly in these tubes is taken up by the roots,\nconducted by the fibres to all parts, and given off (transpiration) by\nthe pores of the leaves. But these pores also serve for the breathing\nof plants, being connected with the air-containing intercellular\npassages; through these air-spaces, which serve for the a\u00ebration of\nthe higher plant-body, air and moisture can enter, and oxygen be given\noff in respiration. Finally, many of the vascular plants have special\nglands that serve for secretion (of oil, resin, etc.). In the higher\nflowering plants this division of work among the various digestive\norgans gives rise to a very complicated apparatus for nutrition. Among\nthe many remarkable structures that have been developed in this way by\nadaptation to special conditions we may particularly note the organs\nfor catching and digesting insects in the insect-eating plants, the\nEuropean _drosera_ and _utricalaria_, and the tropical _nepenthas_ and\n_dion\u00e6a_.\n\nThe long scale of evolutionary forms which we find in the tissue\nanimals (metazoa) leads up uninterruptedly from the simplest to\nthe most elaborate physiological functions and a corresponding\nmorphological complexity of organs. The two principal divisions of\nthe metazoa are chiefly distinguished by the circumstance that in the\nc\u0153lenteria one single system of organs, the gastro-canal system,\ndischarges the whole (or most part) of the partial functions of\nnutrition; while in the c\u0153lomaria they are usually distributed among\nfour different systems of organs, each of which is made up of a number\nof organs. To an extent, we find once more in each great division\ncharacteristic types of organization. However, comparative ontogeny\nteaches us that all these various structures have been developed\nfrom one simple fundamental form, as I have shown in my theory of the\ngastr\u00e6a (1872).\n\nThe older research into the origin of the nutritive apparatus in\nthe metazoa--especially its chief part, the alimentary or gastric\ncanal--had led to the erroneous belief that in several groups of the\nmetazoa it owed its origin to very different growth-processes, and\nthat particularly in the higher vertebrates (the amniotes) it was\na comparatively late product of evolution. On the other hand, the\ncomparative study of the embryology of the lower and higher animals\nled me thirty-four years ago to the opposite conclusion, that a simple\ngastric sac was the first and oldest organ of all the metazoa, and that\nall the different forms of it had been developed from this primitive\ntype. I gave this view in my _Biology of the Sponges_ in 1872; and I\ndeveloped and established it in my _Studies of the Gastr\u00e6a Theory_ in\n1873. In the latter book I also worked out the important conclusions\nthat follow from this monistic reform of the theory of germinal layers\nfor the phylogenetic natural classification of the animal kingdom.\nI began with the consideration of the simplest sponges (_olynthus_)\nand cnidaria (_hydra_). The whole body of these lowest and oldest\nof the c\u0153lenteria is in essence nothing but a round, oval, or\ncylindrical gastric vesicle, a digestive sac, the thin wall of which\nconsists of two simple layers of cells. The outer layer (the ectoderm\nor skin-layer) is the covering layer of the external skin (epidermis);\nit is the instrument of sensation and movement. The inner layer of\ncells (entoderm or gastric layer) serves for nutrition; it clothes\nthe simple cavity of the sac, which admits the food by its opening\nand digests it. This opening is the primitive mouth (_prostoma_ or\n_blastoporus_), the inner cavity itself the primitive gut (_progaster_\nor _archenteron_). I proved that there was the same composition in\nthe young embryos or larv\u00e6 of many of the lower animals, and showed\nthat the manifold and apparently very different embryonic form of all\nthe higher animals may be reduced to the same common type. To this I\ngave the name of the \"cup-embryo\" or gastric larv\u00e6 (_gastrula_), and\nconcluded, in virtue of the biogenetic law, that it is the palingenetic\nreproduction of a corresponding ancestral form (the _gastr\u00e6a_)\nmaintained until the present by heredity. It was not until much later\n(1895) that Monticelli discovered a modern gastr\u00e6ad (_pemmatodiscus_)\nwhich corresponds completely to this hypothetical ancestor (see the\nlast edition of my _Anthropogeny_, fig. 287). The simplest living forms\nof the sponges (_olynthus_) and the cnidaria (_hydra_) only differ from\nthis hypothetical primitive form of the gastr\u00e6a by a few secondary and\nsubsequently acquired features.\n\nThe classes of the lower animals which we comprise under the name\nc\u0153lenteria (or c\u0153lenterata in the widest sense) generally agree\nin having all the functions of nutrition accomplished exclusively (or\nfor the most part) by a single system of organs, the gastro-canal or\ngastro-vascular system. From their common stem-group, the gastr\u00e6ads,\nthree different stems have been evolved--the sponges, cnidaria, and\nplatodes. All these c\u0153lenteria have three features in common: (1)\nThe gastric canal or tube has only one opening--the primitive mouth,\nwhich serves at once for admitting food and ejecting indigestible\nmatter; there is no anus; (2) there is no special body-cavity\n(_c\u0153loma_) distinct from the gastric tube; (3) there is also no\ntrace of a vascular system. All cavities that are found in these lower\nanimals besides the digestive gut-cavity are direct processes from it\n(with the exception of the nephridia in the platodes).\n\nWhile the simple digestive gut is the sole organ of nutrition in the\nstem-group of the gastr\u00e6ads, we find other structures co-operating in\nthe rest of the c\u0153lenteria. The characteristic stem of the sponges\nis distinguished by the piercing of the wall of the gastric vesicle\nwith several holes. Through these water pours into the body, bringing\nwith it the small particles of food which are received and digested\nby the ciliated cells of the entoderm; the water emerges again by the\nmouth-opening (_osculum_). The best-known of the sponges is the common\nbath-sponge (_euspongia officinalis_), the horny skeleton of which\nwe use daily in washing. In these and most other sponges the large,\nunshapely body is traversed by a number of branching canals, on which\nthere are thousands of tiny vesicles, produced by the multiplication\nof a simple gastric vesicle of the primitive sponge (_olynthus_). Each\nof these ciliated chambers is really a tiny gastr\u00e6a, a \"person\" of the\nsimplest character (_cf._ chapter vii.). Hence we may regard the whole\nsponge-body as a gastr\u00e6ad-stock (_cormus_).\n\nThe large group of the cnidaria offers a long series of evolutionary\nstages, from very small and simple to very large and elaborate forms.\nSome of them remain at a very low stage, as does our common green\nfresh-water polyp (_hydra viridis_), which only differs from the\ngastr\u00e6a by a few variations in tissue and the formation of a crown of\nfeelers about the mouth. Most of the polyps form stocks (_cormi_),\nthe individuals shooting out buds which remain joined to the mother\nanimal. In these and all the other stock-forming animals the nutrition\nis communistic; all the food that the individuals get and digest is\nconducted by tubes to the common fund and equally distributed. In all\nthe larger cnidaria the body-wall becomes thicker, and is traversed by\nbranching gastro-canals; these convey the nutritive fluid to all parts\nof the body.\n\nWhile the fundamental type in the cnidaria is radial (determined\nby the crown of radiating feelers or tentacles that surrounds the\nmouth), it is bilateral-symmetrical in the platodes or \"flat-worms\"\n(_plathelminthes_). In this animal-stem, moreover, the lowest forms,\nthe platodaria (also called _cryptoc\u0153la_ and _ac\u00e6la_) come very\nclose to the gastr\u00e6a. But most of the platodes are distinguished from\nthe rest of the c\u0153lenteria by the formation of a pair of nephridia\n(renal canals or water-vessels), thin tubes which, as excretory organs,\nremove from the body the unusable products of metabolism, the urine.\nHere we have a second organ of nutrition, the gut tube, added to the\nfirst. In the lower platodes this remains very simple. As a rule, a\ngullet tube (pharynx) is formed by the hollowing out of the mouth, as\nin the corals; and as in the case of the latter branched canals, which\nconduct the nutritive sap from the stomach to distant parts of the\nbody, grow out of the stomach, in the larger coil-worms (_turbellaria_)\nand suction-worms (_trematodes_). On the other hand, the gut atrophies\nin the tape-worms (_cestodes_); as these parasites live in the\nintestines or other organs of animals, they can obtain their nutritive\nsap directly from them through the surface of the skin.\n\nThe more highly organized c\u0153lomaria differ from the simpler\nc\u0153lenteria chiefly by the greater complexity in the structure\nand functions of their apparatus of nutrition. As a rule, these\nfunctions are divided between four groups of organs, which are not yet\ndifferentiated in the c\u0153lenteria--namely: 1, organs of digestion\n(gastric system); 2, organs of circulation (vascular system); 3, organs\nof breathing (respiratory system); and 4, organs of excretion (renal\nsystem). Moreover, in the c\u0153lomaria the gastric canal has usually\ntwo openings, the mouth and the anus. Finally, they all have a special\nbody-cavity (_c\u0153loma_); this is quite separate from the gastric\ncanal, which is suspended in it, and serves for the formation of the\nsexual cells. It is formed in the embryo by the hollowing out and\ncutting off of a pair of sacs (c\u0153lom-pouches) from the gut near the\nmouth; the pouches touch, and then coalesce, as their division-walls\nbreak down. If a part of the dividing wall remains, it serves as\nmesentery to fasten the gut to the body-wall. The action of the four\ngroups of alimentary organs remains very simple in the lowest and\noldest c\u0153lomaria, the worms (_vermalia_); but in the other higher\nanimals, which have been evolved from these, they have very varied and\noften complicated features.\n\nIn the great majority of the c\u0153lomaria the gastric system forms a\nhighly differentiated apparatus, composed, as in man, of a number of\ndifferent organs. The food is usually taken in by the mouth, ground\nup by the jaws or the teeth, and softened with saliva, which the\nsalivary glands pour into the cavity of the mouth. From the mouth\nthe pulpy food passes in swallowing into the gullet, which often has\nglandular appendages, and from this through the narrow esophagus into\nthe stomach. This most important part of the alimentary apparatus is\noften divided into several sections, one of which (the masticating\nstomach) is armed with teeth and prepared for a further triturition\nof solid pieces, while the other (the glandular stomach) produces the\ndissolving gastric juice. The liquefied food (_chylus_) then passes\ninto the small intestine (_ileum_), which has to absorb it, and is as a\nrule the longest section of the alimentary canal. A number of different\ndigestive glands open into this intestine, the most important of them\nbeing the liver. The small intestine is often sharply distinguished\nfrom the large intestine (_colon_), the last large section of the\nalimentary canal; into this also a number of glands and blind\nintestines open. The last portion of it is called the _rectum_, and\nthis removes the indigestible remnants of the food (_f\u00e6ces_) through\nthe anus.\n\nThis general plan of the alimentary system, which is common to most\nof the c\u0153lomaria in its chief features, is very much modified in\nthe various groups of these animals and adapted to their several\nconditions of nutrition. The simplest structures are found in many of\nthe vermalia; the lowest forms of these, the rotifers, and especially\nthe gastrotricha, still closely resemble their platode ancestors, the\nturbellaria. The higher type of animal-stems which have been evolved\nfrom them are partly distinguished by special structures. Thus the\nmollusks have a characteristic masticating apparatus; on their tongue\nthere is a hard plate (_radula_) armed with a number of teeth, which\ngrinds against a hard upper jaw, and so breaks up the food. In most of\nthe articulates this work is done by side-jaws, which consist of hard\nrods and represent modified bones. The vertebrates and the closely\nrelated tunicates are distinguished by the conversion of the first\nsections of the alimentary canal into a characteristic respiratory\napparatus (gills). But the construction of the various sections of\nthe gastro-canal also varies a good deal in the small groups of\nthe c\u0153lomaria, as it depends to a great extent on the nature of\nthe food and the conditions in which it is got and prepared. The\nlargest expenditure of mechanical and chemical energy is needed for\na voluminous solid vegetal diet. Hence the alimentary canal and its\nmany appendages are longest and most complicated in the plant-eating\nsnails, leaf-eating insects, and grass-eating ruminants. On the other\nhand, they are shortest and simplest in parasitic c\u0153lomaria, which\nderive their fluid food already prepared from the contents of another\nanimal's intestines. In these cases the gut may altogether atrophy; as\nin the _acanthocephala_ among the vermalia, the _entoconcha_ among the\nmollusks, and the _sacculina_ among the crustacea.\n\nThe greater the extent of the body, and the more complex the\norganization of the higher animals, the more necessary it is to have\nan orderly and regular distribution of the nutritive fluid to all\nparts. In the c\u0153lenteria this work is accomplished by the gastric\ncanals (side branches from the gut, opening into its cavity) but in\nthe c\u0153lomaria it is done much better by means of blood-vessels\n(_vasa sanguifera_). These canals do not communicate directly with the\ngastro-canal, but are formed independently of it in the surrounding\nparenchyma of the mesoderm. They take up the filtered and chemically\nimproved food-fluid, which transudes through the intestinal walls, and\nconduct it in the form of blood to all parts of the body. This blood\ngenerally contains millions of cells, which are of great importance\nin metabolism. The blood-cells of the lower c\u0153lomaria are usually\ncolorless (leucocytes), while those of the vertebrates are mostly red\n(rhodocytes).\n\nThe circulation of the blood in most of the c\u0153lomaria is effected\nby a heart, a contractile tube, formed by the local thickening of\na skin-vessel, which contracts and beats regularly by means of its\nmuscular bands. Originally two of these skin-vessels were developed in\nthe abdominal wall--a dorsal vessel in the upper and ventral vessel\nin the lower wall (as in many of the vermalia). The heart is formed\nfrom the dorsal vessel in the mollusks and articulates, but from the\nventral in the tunicates and vertebrates. The arteries are the vessels\nwhich conduct the blood from the heart; those which conduct it from the\nbody to the heart are the veins. The finest branchlets of both kinds\nof vessels, which form the connecting link between them, are called\ncapillaries; these immediately effect the interchange of matter in the\ntissues by osmosis. The blood-vessels co-operate very closely with the\nrespiratory organs.\n\nThe interchange of gases in the organism, which we call breathing or\nrespiration--the taking in of oxygen and giving out of carbonic-acid\ngas--does not require special organs in the lower animals. In these\nit is accomplished by epithelial cells, which clothe the surface of\nthe body--the ectoderm of the outer skin layer and the entoderm of\nthe inner gut-covering. As nearly all these c\u0153lenteria live in the\nwater, or (as parasites) in some fluid that contains air, and as these\nfluids are constantly pouring in and out of the body, the exchange of\ngases is accomplished at the same time. But in the higher animals this\nis rarely found, only in the small animals of simple construction (such\nas the rotifers and other vermalia, and the smallest specimens of the\nmollusca and articulata). The majority of these c\u0153lomaria attain a\nconsiderable size, and so require special organs; these afford a larger\nsurface for the exchange of gases in the limited space, and accomplish\na very peculiar chemical work as the localized organs of respiration.\nThey fall into two groups according to the nature of the environment;\ngills for breathing in water and lungs for breathing on land. The\nlatter take the oxygen directly from the atmosphere, and the former\nfrom the water, in which atmosphere air is contained in solution.\n\nThe instruments of water-respiration which we call gills (_branchi\u00e6_)\nare generally attenuated parts or processes of the outer skin or the\ninner gastric skin; hence we distinguish the two chief forms, external\nand internal gills. Both are richly provided with blood-vessels which\nbring the blood from the body for the purpose of a\u00ebration. Cutaneous\nor external gills are especially found in the vertebrates, in the form\nof threads, combs, leaves, pencils, tufts of feathers, etc., which are\ndrawn out from the entoderm as local processes of the outer skin, and\nafford a wide surface for the interchange of gases between the body\nand the water. In the mollusca there are usually a pair of comb-shaped\ngills near the heart; in the articulates there are several pairs,\nrepeated in the different segments of the body. Gastric or internal\ngills are peculiar to the vertebrates and the next-related tunicates,\nwith a small group of the vermalia, the enteropneusta. In these the\nfore-gut or head-gut is converted into a gill-organ, the wall of which\nis pierced with gill-fissures; the water that has been taken in by the\nmouth passes away through the outer openings of these fissures. In the\nlower aquatic vertebrates (acrania, cyclostoma, and fishes) the gills\nare the sole organs of breathing; in the higher animals, that live in\nthe air, they fall into disuse, and their place is taken by lungs.\nNevertheless, heredity is so tenacious that we find from three to five\npairs of rudimentary gill-clefts in the embryo right up to man, though\nthey have long since ceased to have any function. This is one of the\nmost interesting of the palingenetic facts that prove the descent of\nthe amniotes (including man) from the fishes.\n\nThe group of the aquatic echinoderms has some very peculiar features of\nrespiration. Their body possesses an extensive water-duct, which takes\nin the sea-water and returns it by special openings (skin-pores or\nmadreporites). The many branches of these water-vessels or ambulacral\nvessels fill with water, especially the tiny feelers or feet, which\nextend from the skin in thousands; they serve at once for movement,\nfeeling, and breathing. But many of the echinoderms have also special\ngills--the star-fish have small finger-shaped cutaneous gills on\nthe back, the sea-urchins special leaf-shaped ambulacral gills, the\nsea-cucumbers internal gastric gills (tree-shaped branching internal\nfolds of the rectum).\n\nThe organs of air-breathing are called, in general, lungs (_pulmones_).\nLike the organs of water-breathing, they are formed sometimes from\nthe external and sometimes from the internal covering of the body.\nCutaneous or external lungs are found in several groups of the\nvertebrates. Among the mollusks the land-dwelling lung-snails have\nacquired a lung-sac by change in the work of the gill cavity: among\nthe articulata the lung-spiders and scorpions have two or more\ntrachea-lungs; that is to say, cutaneous sacs, in which are enclosed\nfanwise a number of trachea-leaves. In the other air-breathing\narticulates (tracheata) we find, instead of these simple or branched,\nand often bushlike, air-tubes (_trache\u00e6_), which spread through the\nwhole body and conduct the air direct to the tissues. They take the\nair from without by special air-holes in the skin (_stigmata_ and\n_spiracula_). The myriapods and insects generally have numbers of\nair-holes; the spiders only one or two, more rarely four, pairs. When\nthese air-tube animals return to an aquatic life (as happens with the\nlarv\u00e6 of various groups of insects), the outer air-holes close up, and\nnew thread-shaped or leaf-shaped trachea-gills are formed, which take\nthe air from the surrounding water by osmosis. The oldest and lowest\ntracheata are the primitive air-tube animals, or protracheata, and form\nthe link between the older annelids and the myriapods. They have a\nnumber of clusters of short air-tubes distributed over the whole skin,\nand it is clear that these have been evolved from simple skin-glands by\nchange of function.\n\nGastric or internal lungs are only found in the higher animals, to\nwhich we give the name of quadrupeds (or _tetrapoda_), the amphibia and\namniotes, and their fishlike ancestors, the dipneusta. These internal\nlungs are sac-shaped folds of the fore-gut, formed originally from the\nswimming-bladder (_nectocystis_) of the fishes by change of function.\nThis air-filled bladder, a sac-shaped appendage of the gullet, merely\nserves the purpose of a hydrostatic organ, by varying the specific\nweight, in the fishes. When the fish wishes to descend it contracts\nthe bladder and becomes heavier; it rises to the top by inflating it\nagain. The lungs were formed by the adaptation of the blood-vessels\nin the wall of the swimming-bladder to the interchange of gases. In\nthe oldest living lung-fishes (_ceratodus_) it is still a simple sac\n(_monopneumones_=one-lunged); in the others the simple gullet-cavity\ndivides early into a pair of sacs (_dipneumones_, two-lunged). The\nwind-pipe (_trachea_--not to be confused with the organ of the same\nname in the tracheata) is formed by the lengthening of their stalk\nand strengthening of it with cartilaginous rings. At the anterior end\nof the trachea we find already formed in the amphibia the larynx, the\nimportant organ of voice and speech.\n\nThe function of removing unusable matter is not less important to the\norganism than breathing. Just as breathing gets rid of the poisonous\ncarbonic acid, so the kidneys remove fluid and solid excreta in the\nshape of urine; these are partly acid (uric acid, hippuric acid, etc.),\npartly alkaline (urea, guanine, etc.). In most of the c\u0153lomaria\nspecial organs for removing these would be superfluous, as this is\naccomplished (like breathing) by the stream of water that is constantly\npassing through the whole body. But with the platodes we begin to\nfind important excretory organs in the nephridia, a pair of simple\nand ramified canals which lie on either side of the gut, and open\noutward. These primitive renal canals are transmitted by the platodes\nto the vermalia, and by these to the higher stems of the c\u0153lomaria.\nIn the latter they generally open by special funnels into the inner\nbody-cavity, which serves as first receptacle for the urine. Their\nouter opening sometimes (primarily) goes through the outer skin at the\nback (excretory pores), sometimes (secondarily) to the rectum, and\nso out through the anus. The oldest articulates, the annelids, have\na pair of nephridia in each segment of the body; each renal canal,\nor segmental canal, consists of three sections, an inner funnel\nwhich opens into the body-cavity, a middle glandular section, and an\nexternal bladder that ejects the urine by contraction. The disposition\nof the renal system in the internally articulated vertebrates is very\nsimilar to this; but now complicated structures begin to appear, a\npair of compact kidneys (_renes_), which are made up of a number of\nbranching nephridia. Three generations of kidneys succeed each other,\nas phylogenetic stages of evolution--first the primary fore-kidneys\n(_protonephros_), in the middle the secondary primitive kidneys\n(_mesonephros_), and last the tertiary after-kidneys (_metanephros_).\nThe latter are only reached in the three highest classes of\nvertebrates, reptiles, birds, and mammals. Mollusks also have a couple\nof compact kidneys. They are developed from a pair of nephridia, the\nfunnels of which open internally into the heart-pouch (the remainder of\nthe reduced body-cavity); at the back they open outward. The crustacea\nalso have generally a pair of renal canals. On the other hand, the\nprotracheata (the stem-forms of the air-tube animals) have segmental\nnephridia, a pair to each joint inherited from their annelid ancestors.\nThe rest of the tracheata, the myriapods, spiders, and insects, have,\ninstead of these, Malpighi tubes, funnel-shaped glands that arise from\nthe entodermal rectum, sometimes one pair or less, sometimes a number\nin a cluster.\n\nWhile most plants are purely plasmodomous, and most animals\nplasmophagous, there are nevertheless in both organic kingdoms a\nnumber of species (especially the lower) whose metabolism has assumed\npeculiar forms by their relations to other organisms. To this class\nbelong especially the saprosites and parasites. By saprosites are\nunderstood those plants and animals which feed entirely or mostly\non the corpses of other animals, or the decomposed matter which is\nunfit for the food of higher animals. Among the unicellular protists\nmany of the bacteria, especially, belong to this class, and also many\nfungilla (_phycomycetes_); among the metaphyta the fungi (mycetes),\nand among the metazoa the sponges. I have already spoken of the many\npeculiarities of metabolism in the ubiquitous bacteria; while many of\nthem cause putrefaction, they at the same time feed on the parts of\nother organisms which have died. The fungi feed for the most part on\nthe decayed remains of plants and the products of putrefaction which\naccumulate on the ground. In this character of scavengers they play the\nsame important part on land as the sponges do at the bottom of the sea.\nBut a number of small groups of the higher plants and animals have, as\na secondary habit, turned to saprositism. Among the metaphyta we have\nespecially the monotropea (to which our native asparagus, _monotropa\nhypopitys_, belongs) and many orchids (_neottia_, _corallorhiza_). As\nthey find their plasm directly in the decayed matter in the woods,\nthey have lost their chlorophyll and green leaves. Among the metazoa\nmany of the vermalia, and some of the higher animals, such as the\nrain-worm and many tube-dwelling annelids (the mud-eaters, _limicol\u00e6_),\netc., live on putrid matter. The organs which their nearest relatives\nuse for obtaining, breaking up, and digesting food (eyes, jaws,\nteeth, digestive glands) have been entirely or mostly lost by these\nsaprosites. Many of them form a transitional type to the parasites.\n\nBy parasites, in the narrower sense, we understand, in modern biology,\nonly those organisms which live on others and derive their nourishment\nfrom them. They are numerous in all the chief divisions of the plant\nand animal kingdoms, and their modifications are of great interest\nin connection with evolution. No other circumstance has so profound\nan influence on the organism as adaptation to a parasitic existence.\nMoreover, there is no other section in which we can follow, step\nby step, the course of the degeneration which is caused, and show\nclearly the mechanical nature of the process. Hence the science of\nparasites--parasitology--is one of the soundest supports of the theory\nof descent, and provides an abundance of the most striking proofs of\nthe much-contested inheritance of acquired characteristics.\n\nAmong the unicellular organisms, the bacteria are the most conspicuous\ninstances of manifold adaptation to parasitic habits. As we count\nthese unnucleated protozoa among the oldest and simplest organisms,\nand trace them directly by metasitism to the plasmodomous chromacea,\nit is very probable that they turned to parasitism very early in the\nhistory of life. Even a part of the monera (in which group we must\nplace the bacteria on account of their lack of a nucleus) found it\nconvenient and advantageous to prey on other protists and assimilate\ntheir plasm directly, instead of going through the laborious process\nof carbon assimilation themselves in the hereditary fashion. This is\nalso true of the large class of the sporozoa or fungilla (_gregarin\u00e6_,\n_coccidia_, etc.), real nucleated cells, which have adapted themselves\nin various ways to parasitic habits. Many of them live in the\nrectum, the c\u0153lum, or other organs of the higher animals (the\ngregarin\u00e6, especially in the articulates); others in the tissues (for\ninstance, the sarcosporidia in the muscles of mammals, the coccidia\nand myxosporidia in the liver of vertebrates). A good many of them\nare \"cell-parasites,\" and live inside the cells of other animals,\nwhich they destroy; such are the h\u0153mosporidia, which destroy the\nblood-cells in man, and so cause intermittent fever.\n\nAmong the multicellular metaphyta it is particularly the fungi that\nhave taken to parasitism in various ways. Many of them are, as is\nknown, the most dangerous enemies of the higher animals and plants. The\nvarious species of fungi cause certain diseases by their poisonous\n(chemical) action on the tissues of their host. It is well known how\nour most important cultivated plants, the vine, potato, corn, coffee,\netc., are threatened by fungoid diseases; and this is also true of many\nof the lower and higher animals. It is probable that the fungi have\nbeen evolved polyphyletically by metasitism from the alg\u00e6.\n\nAmong the higher metaphyta we find parasitism in many different\nfamilies, especially orchids, rhinanthacea (_orobranche_,\n_lathraca_), convolvulacea (_cuscuta_), aristolochiacea, loranthacea\n(_viscum_, _loranthus_), rafflesiacea, etc. These various kinds of\nflowering-plants often grow to resemble each other by convergence\n(that is to say, by their common adaptation to parasitic life); they\nlose their green leaves, the plasmodomous chlorophyll of which is of\nno further use to them. Frequently rudimentary leaves are left on them\nin the form of colorless scales. For the purpose of clinging to the\nplants they live on, and penetrating into their tissues, they evolve\nspecial clinging apparatus (haustoria, suctorial cups, creepers). Their\nstalks and roots are also modified in a characteristic way. The whole\nproductive force of these parasites is expended on their sexual organs;\n_rafflesia_ has the largest flowers there are, more than a yard in\ndiameter.\n\nParasitism in the metazoa (in all groups) is even more frequent and\ninteresting than in the metaphyta. The mollusks and echinoderms\nshow the least disposition for it, and the platodes, vermalia, and\narticulates the most. Even among the gastr\u00e6ada, the common ancestral\ngroup of the metaphyta, we find parasites (kyemaria and gastremaria).\nThe protection they find inside their hosts is probably the reason\nwhy these oldest of the metazoa have remained unchanged to the\npresent day. Real parasites are not numerous among the sponges and\ncnidaria. But they are very numerous among the platodes. The suctorial\nworms (_trematodes_) live partly externally (as ectoparasites)\non other animals and partly inside them (as endoparasites), and\nproduce serious diseases in them. They have lost the vibratory\ncoat of their free-living ancestors, the turbellaria, and acquired\nclinging apparatus instead. The tape-worms (_cestodes_), which live\nentirely in the interior of other animals, and are descended from the\nsuctorial worms, have lost their gastro-canal; they are nourished by\nimbibition through the skin. The same degeneration is found in the\nitchworms (_acanthocephala_) among the vermalia, the parasitic snails\n(_entoconcha_) among the mollusks, and the root-crabs (_rhizocephala_)\namong the crustacea.\n\nThe class of crustacea affords the most numerous and most instructive\nexamples of degeneration through parasitism, because in this class it\nis found polyphyletically in very different orders and families, and\nbecause their highly organized body shows every stage of degeneration\ntogether in the different organs. The free-living crustacea generally\nmove about very rapidly and ingeniously; their numerous bones are\nwell jointed and excellently adapted for the most varied methods of\nlocomotion (running, swimming, climbing, digging, etc.); their organs\nof sense are highly developed. As these are no longer used when\nthey take to parasitism, they atrophy and gradually disappear. The\nyounger crustacea all proceed from the same characteristic form of\nthe _nauplius_, and swim freely about; later, when they settle down\nto parasitic habits, their organs of sense and locomotion atrophy. As\nFritz M\u00fcller-Desterro showed in his famous little work, _For Darwin_\n(1864), forty years ago, the crustacea afford most luminous proofs of\nthe theory of descent and selection, and of progressive heredity and\nthe biogenetic law. These facts are the more important as the crab\nundergoes the same degeneration by parasitic habits in a number of\ndifferent orders and families.\n\nFrom parasitism we must entirely distinguish that intimate life-union\nof two different organisms which we called symbiosis or mutualism.\nHere we have an association of two living things for their mutual\nbenefit, while the parasite lives entirely at the expense of his\nhost. Symbiosis is found among the protista, being very wide-spread\namong the radiolaria. In the gelatinous envelope (_calymma_) which\nencloses the central capsule of their unicellular bodies we find a\nnumber of motionless yellow cells (_zooxanthella_) scattered. These\nare protophyta or (as it is said) \"unicellular alg\u00e6\" of the class of\npaulotomea (_palmellacea_). They receive protection and a home from the\nradiolaria, grow plasmodomously, and multiply by rapid segmentation.\nA large part of the starch-flour and the plasm which they form by\ncarbon-assimilation goes as food directly to the radiolarium-host; the\nother part of the xanthella goes on growing and multiplying. Similar\nyellow zooxanthella or green zoochlorella are found as symbionta in the\ntissues of many animals. Our common fresh-water polyp (_hydra viridis_)\nowes its green color to the zoochlorella which live in great numbers\non the ciliated cells of its entoderm (the digestive gut-epithelium).\nIn general, however symbiosis is rarer in the metazoa than in the\nmetaphyta. In the latter case it is the fundamental feature of a whole\nclass of plants, the lichens. Each lichen consists of a plasmodomous\nplant (sometimes a protophyte, sometimes an alga) and a plasmophagous\nfungus. The latter affords a home, protection, and water to the green\nalga, which repays the service by providing food.\n\n\n\n\nXI\n\nREPRODUCTION\n\n\n Reproduction and generation--Sexual\n and asexual reproduction--Superfluous\n growth--Monogony--Self-cleavage--Budding--Formation of\n spores--Amphigony--Ovum and sperm-cell--Hermaphrodite formation\n and separation of the sexes--Hermaphrodism and gonochorism\n of the cells--Monoclinism and diclinism--Mon\u0153cism and\n di\u0153cism--Alternation of sex-division--Sexual glands of\n the histona--Hermaphroditic glands--Sexual ducts--Generative\n organs--Parthenogenesis--P\u00e6dogenesis--Metagenesis--Heterogenesis--\n Strophogenesis--Hypogenesis--Hybridism--Generation of hybrids and\n the species--Graduation of forms of reproduction.\n\n\nWhile nutrition secures the maintenance of the organic individual,\nreproduction insures that of the organic species, or the group of\ndefinite forms which we distinguish from others by the name \"species.\"\nAll individuals are more or less restricted in the duration of their\nlives, and die off after the lapse of a certain time. The succession\nof individuals, connected by reproduction and belonging to a species,\nmakes it possible for the specific form itself to last for ages. In\nthe end, however, the species is temporary; it has no \"eternal life.\"\nAfter existing for a certain period, it either dies or is converted by\nmodification into other forms.\n\nThe rise of new individuals by reproduction from parent organisms\nis a natural phenomenon with definite time-restriction. It cannot\nhave continued from eternity on our planet, as the earth itself is\nnot eternal, and even long after its formation was incapable of\nsupporting organic life on its surface. This only became possible when\nthe surface of the glowing planet had sufficiently cooled for liquid\nwater to settle on it. Until this stage carbon could not enter into\nthose combinations with other elements (oxygen, hydrogen, nitrogen, and\nsulphur) which led to the formation of plasm. As I intend to deal with\nthis process of _archigony_, or spontaneous generation, in a special\nchapter, I leave it for the present, and confine myself to the study of\n_tocogony_, or parental generation.\n\n * * * * *\n\nThe various forms of tocogony, or the reproduction of living things,\nare generally divided into two large groups; on the one hand there is\nthe simple form of asexual generation (monogony), and on the other the\ncomplex form of sexual generation (amphigony). In asexual generation\nthe action of one individual only is needed, this providing a product\nof transgressive (redundant) growth which develops into a new organism.\nIn sexual generation it is necessary for two different individuals to\nunite in order to produce a new being from themselves. This amphigony\n(or _generatio digenea_) is the sole form of reproduction in man and\nmost of the higher animals. But in many of the lower animals and most\nof the plants we find also asexual multiplication, or monogony, by\ncleavage or budding. In the lowest organisms, the monera and many of\nthe protists, fungi, etc., the latter is the only form of propagation.\n\nStrictly speaking, monogony is a universal life-process; even the\nordinary cell-cleavage, on which depends the growth of the histona, is\na cellular monogony. Hence historical biology must say that monogony\nis the older and more primitive form of parental generation, and\nthat amphigony was secondarily developed from it. It is important to\nemphasize this because, not only some of the older writers, but even\nsome recent ones, regard sexual generation as a universal function of\norganisms, and declare that it dates from the very beginning of organic\nlife.\n\nThe complex and frequently very intricate phenomena of sexual\ngeneration, as we find them in the higher organisms, become\nintelligible to us when we compare them with the simpler forms of\nasexual generation at the lowest stages of life. We then learn that\nthey are by no means unintelligible and supernatural marvels, but\nnatural physiological processes, which, like all others, may be traced\nto the action of simple physical forces. The form of energy which\nlies at the root of all tocogony is _growth_ (_crescentia_). And as\nthis phenomenon is also the cause, in the form of gravitation, of the\nformation of crystals and other inorganic individuals, we do away with\nanother of the boundaries which people would establish between organic\nand inorganic nature. Reproduction is a kind of nutrition and growth of\nthe organism beyond the individual standard, building up a part of it\ninto a whole. This _limit_ of individual size is determined for each\nspecies by two factors--the inner constitution of the plasm, which is\ninherited, and the dependence on the outer environment, which controls\nadaptation. When this limit has been passed, the transgressive growth\ntakes the form of reproduction. Every species of crystal has also a\ndefinite limit of growth; when this is passed, new crystal-individuals\nare formed in the mother-water on the old individual, which grows no\nfurther.\n\nAsexual or monogenetic tocogony (also called \"vegetative\nmultiplication\") is always effected by a single organic individual,\nand so must be traced to its transgressive growth. When this affects\nthe entire body as a total growth, the whole dividing into two or\nmore equal parts, we call the monogenetic process division (or\nsegmentation). But when the growth is partial, and affects only a\npart of the individual, or when this special part separates from\nthe generating organism in the form of a bud (_gemma_), the process\nis called budding or gemmation (_gemmatio_). Hence the essential\ndifference between the two forms of generation is that in division the\nparent disappears in its partial products (children); these are of\nthe same age and form. But in budding the generating parent retains\nits individuality; it is larger and older than the young bud. This\nimportant difference between division and gemmation, which is often\noverlooked, holds good both for protists (unicellulars) and histona\n(multicellulars). The fact that in division the individual as such\nis destroyed is a sufficient refutation of Weismann's theory of the\nimmortality of the unicellulars. (See above, and also the _Riddle_,\nchapter xi.)\n\nReproduction by division is by far the most common of all forms of\npropagation. It is the normal form of monogony, not only in many of the\nprotists, but also in the tissue-cells which compose the tissues of\nthe histona. It is, moreover, the sole method of propagation for most\nof the monera, both chromacea and bacteria, which are in consequence\noften comprised under the title of \"cleavage-plants\" (_schizophyta_).\nSelf-cleavage is also found among the higher multicellular\norganisms--namely, the cnidaria (polyps, medus\u00e6). It usually takes the\nform of division into two parts (_dimidiatio_ or hemitomy), the body\nsplitting into two equal halves. The plane of division is sometimes\nindefinite (fragmentary-cleavage), sometimes coincident with the long\naxis (length-cleavage), sometimes with the transverse axis, vertical\nto the long axis (transverse-cleavage), and less frequently with a\ndiagonal axis (oblique-cleavage). When the segmentation of a cell\nproceeds so rapidly that the transverse-cleavage follows immediately\non the length-cleavage, and the two are at length made to coincide,\ntwofold division is changed into fourfold division. And when the\nprocess is repeated in quick succession, and the body falls at last\ninto a number of small and equal pieces, we have manifold division\n(polytomy); as in the spore-formation of the sporozoa and rhizopoda,\nand in the embryonic sac of the phanerogams.\n\nAsexual propagation by budding is chiefly distinguished from\nsegmentation by the fact that the determining transgressive growth is\nonly partial in the one and total in the other. The bud produced is,\ntherefore, younger and smaller than the parent from which it issues;\nthe latter may replace the lost part by regeneration and produce a\nnumber of buds simultaneously or successively without losing its\nindividuality (whereas this is destroyed in division). Propagation\nby budding is rare among the protists, and more common among the\nhistona--that is, with most of the tissue-plants and the lower,\nstock-forming, tissue-animals (c\u0153lenteria and vermalia). Most stocks\n(cormi) are formed by a sprout or person shooting out buds which remain\nunited to it. The layer and shoots of tissue-plants are detached\nbuds. The two chief kinds of gemmation are terminal and lateral.\nTerminal budding takes place at the end of the long axis, and is not\nfar removed from transverse division (for instance, the strobilation\nof the acrasped\u00e6 medus\u00e6 and the chain tape-worms). Lateral budding is\nmuch more common; it determines the branching of trees and generally of\ncomplex plants, and also of the tree-shaped stocks of sponges, cnidaria\n(polyps, corals), bryozoa, etc.\n\nA third form of asexual reproduction is the formation of spores or\n\"germ-cells,\" which are usually produced in great numbers inside the\norganism, then detached from it, and developed into new organisms\nwithout needing fertilization. The spores are sometimes motionless\n(rest-spores or paulospores); sometimes they have one or more lashes\nwhich enable them to swim about (rambling-spores or planospores).\nThis monogenetic propagation is very common among the protists, both\nprotophyta and protozoa. Among the latter the sporozoa (gregarin\u00e6,\ncoccidia, etc.) are remarkable for the passing away of the whole\nunicellular organism in the formation of spores; in this case and\nin many of the rhizopods (_mycetozoa_) the process coincides with\nmanifold cell-division. In other cases (radiolaria, thalamophora)\nonly a portion of the parental cells is used for the production of\nspores. Spore-formation is very common among the cryptogams; here it\nusually alternates with sexual propagation. The spores are generally\nformed in special spore-capsules (sporangia). In the flowering plants\n(anthophyta) sporogony has disappeared. It is found at times in the\ntissue-animals (in the fresh-water sponges); in this case the sporangia\nare called _gemmul\u00e6_.\n\nThe essential feature of sexual generation is the coalescence of two\ndifferent cells, a female ovum (egg-cell) and a male sperm-cell.\nThe simple new cell which arises from the blending of these is the\nstem-cell (_cytula_), the stem-mother of all the cells that make up\nthe tissues of the histon. But even among the unicellular protists\nwe find in many places the beginnings of sexual differentiation; it\nis foreshadowed in the blending or copulation of two homogeneous\ncells, the gameta. We may conceive this process, or zygosis, as a\npeculiar and very favorable kind of growth, that is connected with a\nrejuvenescence of the plasm; the latter is enabled to propagate by\nrepeated cleavage through the mixing of the two different plasma-bodies\non either side (_amphimixis_). When these two gameta become unequal\nand differ in size and shape, the larger female body is called the\nmacrogameton or macrogonidion, and the smaller, male part, the\nmicrogameton or microgonidion. Among the histona the first is called\nthe egg-cell (_ovulum_), and the latter the sperm-cell (_spermium_, or\n_spermatozoon_). As a rule the latter is a very mobile ciliated cell,\nthe former an inert or am\u0153boid cell. The vibratory movements of the\nsperm-cells serve for approaching the ovulum in order to fertilize it.\n\nThe qualitative difference between the two copulating sexual cells\n(_gonocyta_), or the chemical difference between the ovoplasm of the\nfemale and the sperm-plasm of the male cell, is the first (and often\nthe only) condition of amphigony; subsequently we find in addition (in\nthe higher histona) a very elaborate apparatus of secondary structures.\nWith this chemical difference is associated a peculiar double form of\nsensitive perception and an attraction based thereon, which is called\nsexual chemotaxis or erotic chemotropism. This \"sex-sense\" of the two\ngonocyta, or elective affinity of the male androplasm and the female\ngynoplasm, is the cause of mutual attraction and union. It is very\nprobable that this sexual sense-function, akin to smell or taste, and\nthe movements it stimulates, are located in the cytoplasm of the two\nsex-cells, while heredity is the function of the caryoplasm of the\nnucleus. (_Cf._ the _Anthropogeny_, chapters vi. and vii.)\n\nThe sexual difference between the two forms of gonoplasm, the ovoplasm\nof the female and spermoplasm of the male cell, is noticeable at the\nvery beginning of sexual differentiation in the different sizes of\nthe copulating gameta, and later in their increasing divergence as to\nshape, composition, movement, etc. It leads further to the distribution\nof the germinal regions (in which the sex-cells are formed) into two\ndifferent individuals. When the ovum and the sperm-cell are produced in\none and the same individual, we call this an hermaphrodite; and when\nthey are formed in two different individuals (male and female), we\ncall them monosexual, or gonochorists. In accordance with the various\nstages of individuality which we distinguished above (chapter vii.), we\nmay indicate the following stages of hermaphrodism and gonochorism.\n\nSome groups of protists, especially the highly organized ciliated\ninfusoria (_ciliata_), are distinguished by having a separation of\nmale and female plasm within the unicellular organism. The ciliata\npropagate, as a rule, in large numbers by repeated division (by\nindirect cell-cleavage). But this monogony has its limits, and has to\nbe interrupted from time to time by amphigony, a rejuvenation of the\nplasm, which is effected by the conjugation of two different cells and\nthe partial destruction of their nuclear matter. By conjugation is\nmeant the partial and momentary union of two different unicellulars,\nwhile copulation is a total and permanent coalescence. When two\nciliated infusoria conjugate they place themselves side by side, and\nconnect for a time by means of a bridge of plasm. A part of the nucleus\nof each has already divided into two portions, one of which functions\nas the female standing-nucleus (_paulocaryon_) and the other as the\nmale travelling-nucleus (_planocaryon_). The two mobile nuclei enter\nthe plasm-bridge, and move through it, pushing against each other,\ninto the body of the opposite cell; they then coalesce with the deeper\nlying standing-nucleus. When a fresh nucleus has been thus formed (by\n_amphimixis_) in each of the copulating cells, they again separate. The\ntwo rejuvenated cells have once more acquired the power to propagate\nfor a long time by division.\n\nThis peculiar hermaphroditic formation of the cells, which\ndistinguishes the ciliated infusoria and some other protists, and\nwhich we now know in its smallest details through the investigations\nof Richard Hertwig, Maupas, and others, is especially interesting\nbecause it proves that the chemical difference between the female\ngynoplasm and the male androplasm can be found within a single cell.\nThis erotic division of labor is so important that formerly it was\nuniversally ascribed to two different cells. Recent accurate research,\npenetrating into the smallest visible processes of fertilization, has\nshown that the essential feature in the formation of a fresh individual\n(the stem-cell) is the blending of equal portions (hereditary parts)\nof the male and female nuclei; the caryoplasm of the two copulating\ncells is the vehicle of heredity from the parents. The cytoplasm of the\ncell-body, on the other hand, serves the purposes of adaptation and\nnutrition. As a rule the cell-body of the ovulum is very large, and\nis, as a food-store, very richly provided with albumin, fat, and other\nnutritive matter (food-yolk); while the cytoplasm of the sperm-cell is\nvery small, and generally forms a vibrating lash, with which it moves\nalong and seeks the ovum.\n\nIn most of the plants the female and male cells are produced by the\nsame sprout, and in many of the lower animals by one and the same\nperson. This kind of hermaphrodism in \"individuals of the second order\"\nis called monoclinism (\"one-beddedness\"). In many of the higher plants\n(mon\u0153cic stocks) and most of the higher animals we have diclinism\n(\"two-beddedness\")--in other words, the one sprout or person has\nonly male, and the other sprout or person only female, organs--this\nis gonochorism of individuals of the second order. Monoclinism is\ngenerally associated with sedentary life (and often necessary for it),\nand diclinism with free movement. Adaptation to parasitic habits also\nfavors monoclinism; thus, the crabs, for instance, are for the most\npart gonochoristic individuals, but the creeping crabs (_cirripedia_),\nwhich have adopted sedentary (and to an extent parasitic) habits, have\nbecome hermaphrodites in consequence. Many intestinal parasites among\nthe lower animals (such as tape-worms, suctorial worms, wonder-snails),\nwhich live isolated lives inside other animals, have to be\nhermaphroditic and able to fertilise themselves if the species is to be\nmaintained. On the other hand, many hermaphroditic flowers, although\nthey have both sorts of sex-organs, are incapable of fertilizing\nthemselves and have to receive this from insect visitors which carry\nthe pollen from one flower to another.\n\nIndividuals of the third order, which we call stocks (_cormi_) in both\nthe plant and animal worlds, also exhibit varying features in the\nsex-persons which compose them. When male and female diclinic sprouts\nor persons are found side by side on the same stock, we call this\nhermaphrodism of the cormi _mon\u0153cia_ (\"one-housedness\"); this is the\ncase with most of the siphonophora and some of the corals. _Di\u0153cia_\n(\"two-housedness\") is less common: in this one stock has only male and\nthe other only female sprouts or persons, as in poplars and osiers,\nmost of the corals, and some of the siphonophora. The physiological\nadvantages of crossing--the union of sex-cells of different\nindividuals--favor progressive sex-division in the higher organisms.\n\nA comparative study of the features of hermaphrodism and sex-division\nin the plant and animal worlds teaches us that both forms of\nsex-activity are often found in closely related organisms of one and\nthe same group, sometimes even in different individuals of the same\nspecies. Thus, for instance, the oyster is usually gonochoristic, but\nsometimes hermaphroditic; and so with many other mollusks, vermalia,\nand articulata. Hence, the question often raised, which of the two\nforms of sex-division is original, is hardly susceptible of a general\nanswer, or without relation to the stage of individuality and the place\nin classification of the group under discussion. It is certain that in\nmany cases hermaphrodism represents the original feature; for instance,\nin most of the lower plants and many of the stationary animals\n(sponges, polyps, platodes, tunicates, etc.). Where we find exceptions\nin these groups, they are of secondary origin. It is equally certain,\non the other hand, that in other cases the separation of the sexes is\nthe primitive arrangement; as in siphonophor\u00e6, ctenophor\u00e6, bryozoa,\ncirripedia, and mollusks. In these cases the hermaphrodism is clearly\nsecondary in the sense that the hermaphrodites descend originally from\ngonochorists.\n\nIt is only in a few sections of the lowest histona that the two kinds\nof sex-cells arise without a definite location in different parts of\nthe simple tissue, as in a few groups of the lower alg\u00e6 and in the\nsponges. As a rule they are formed only at definite positions and in a\nspecial layer of the tissue-body, and mostly in groups, in the shape\nof sexual glands (_gonades_). These bear special names in different\ngroups of the histona. The female glands are called archegonia in\nthe cryptogams, _nucellus_ (formed from the macrosporangia of the\npteridophyta) in the phanerogams, and ovaries in the metazoa. The male\nglands are called antheridia in the cryptogams, pollen-sacs (formed\nfrom the microsporangia of the ferns) in the phanerogams, and testicles\n(_as spermaria_) in the metazoa. In many cases, especially in aquatic\nlower animals, the ovula (as products of the ovaries) are discharged\ndirectly outward. But, in most of the higher organisms, special sexual\nducts (_gonoductus_) have been formed to conduct both kinds of the\ngonocyta out of the organism.\n\nWhile the two kinds of sexual glands are usually located in different\nparts of the generating organism, there are, nevertheless, a few cases\nin which the sex-cells are formed directly and together from one and\nthe same gland. These glands are called hermaphroditic glands. Such\nstructures are very notable in several highly differentiated groups\nof the metazoa, and have clearly been developed from gonochoristic\nstructures in lower forms. The class of crested medus\u00e6, or ribbed\nmedus\u00e6 (ctenophor\u00e6), contains glasslike, sea-dwelling cnidaria of a\npeculiar and complicated build, which probably descend from hydromedus\u00e6\n(or craspedota). But whereas the latter have very simple gonochoristic\nstructures (four or eight monosexual glands in the course of the\nradial canals or in the gastric wall), in the ctenophor\u00e6 the eight\nhermaphroditic canals run in a meridian arch from one pole of the\ncucumber-shaped body to the other. Each canal corresponds to a ciliary\nstreamer, and forms ovaries at one border and testicles at the other;\nand these are so arranged that the eight intercostal fields (the spaces\nbetween the eight streamers) are alternately male and female. Still\nmore curious are the hermaphroditic glands of the highly organized,\nland-dwelling, and air-breathing lung-snails (_pulmonata_), to which\nour common garden snail (_arion_) and vineyard snail (_helix_) belong.\nHere we have a hermaphroditic gland with a number of tubes, each of\nwhich forms ovaries in its outer part and sperma in the inner. Still\nthe two kinds of sex-cells lead separately outward.\n\nIn most of the lower and aquatic histona both kinds of sex-cells,\nwhen they are ripe, fall directly into the water, and come together\nthere. But in most of the higher, and especially the terrestrial,\norganisms special exits or conducting canals have been formed for the\nsex-products, the sexual ducts (_gonoductus_); in the metazoa the\nfemale have the general name of oviducts and the male spermaducts (or\n_vasa deferentia_). In the viviparous histona special canals serve\nfor the conveyance of the sperm to the ovum, which remains inside the\nmother's body; such are the neck of the archegonium in the cryptogams,\nthe pistil in the phanerogams, and the vagina in the metazoa. At the\nouter opening of these conducting canals special copulative organs are\ndeveloped, as a rule.\n\nWhen the ejected sex-cells do not directly encounter each other (as in\nmany aquatic organisms), special structures have to be formed to convey\nthe fertilizing sperm from the male to the female body. This process of\ncopulation becomes important, as it is associated with characteristic\nfeelings of pleasure, which may cause extreme psychic excitement; as\nsexual love it becomes, in man and the higher animals, one of the most\npowerful springs of vital activity. In many of the higher animals\n(namely, vertebrates, articulates, and mollusks) there are also formed\na number of glands and other auxiliary organs which co-operate in the\ncopulation.\n\nThe manifold and intimate relations which exist, in man and the higher\nanimals (especially vertebrates and articulates), between their sexual\nlife and their higher psychic activity, have given rise to plenty of\n\"wonders of life.\" Wilhelm B\u00f6lsche has so ably described them in his\nfamous and popular work, _The Life of Love in Nature_, that I need only\nrefer the reader to it. I will only mention the great significance of\nwhat are called \"secondary sexual characters.\" These characteristics\nof one sex that are wanting in the other, and that are not directly\nconnected with the sexual organs--such as the man's beard, the woman's\nbreasts, the lion's mane, or the goat's horns--have also an \u00e6sthetic\ninterest; they have, as Darwin showed, been acquired by sexual\nselection, as weapons of the male in the struggle for the female,\nand vice versa. The feeling of beauty plays a great part in this,\nespecially in birds and insects; the beautiful colors and forms which\nwe admire in the male bird of paradise, the humming-bird, the pheasant,\nthe butterfly, etc., have been formed by sexual selection (_cf._ the\n_History of Creation_).\n\nIn various groups of the histona the male sex has become superfluous\nin the course of time; the ovula develop without the need of\nfertilization. That is particularly the case in many of the platodes\n(trematodes) and articulates (crustacea and insects). In the bees we\nhave the remarkable feature that it is only decided at the moment\nof laying the egg whether it is to be fertilized or not; in the one\nevent a female and in the other a male bee is formed from it. When\nSiebold proved at Munich these facts of miraculous conception in\nvarious insects, he was visited by the Catholic archbishop of the\ncity, who expressed his gratification that there was now a scientific\nexplanation possible of the conception of the Virgin Mary. Siebold\nhad, unfortunately, to point out to him that the inference from the\nparthenogenesis of the articulate to that of the vertebrate was not\nvalid, and that all mammals, like all other vertebrates, reproduce\nexclusively from impregnated ova. We also find parthenogenesis\namong the metaphyta, as in the _chara crinita_ among the alg\u00e6, the\n_antennaria alpina_ and the _alchemilla vulgaris_ among the flowering\nplants. We are, as yet, ignorant for the most part of the causes\nof this lapse of fertilization. Some light has been thrown on it,\nhowever, by recent chemical experiments (the effect of sugar and\nother water-absorbing solutions), in which we have succeeded in\nparthenogenetically developing unfertilized ova.\n\nIn the higher animals the complete maturity and development of\nthe specific form are requisite for reproduction, but in many of\nthe lower animals it has been observed recently that ovula and\nsperm-cells are even formed by the younger specimens in the larva\nstage. If impregnation takes place under these conditions, larv\u00e6 of\nthe same form are born. And when these larv\u00e6 have afterwards reached\nmaturity and reproduced in this form, we call the process _dissogony_\n(\"double-generation\"). It is found in many of the cnidaria, especially\nthe medus\u00e6. But if larv\u00e6 propagate by unfertilized ova, and so\nreproduce their kind parthenogenetically, the process is known as\n_p\u00e6dogenesis_ (\"young-generation\"). It is found particularly in the\nplatodes (trematodes) and some of the insects (larv\u00e6 of _cecidomyca_\nand other flies).\n\nIn a large number of lower animals and plants sexual and asexual\ngeneration regularly alternate. Among the protists we find this\nalternation of generation in the sporozoa; among the metaphyta in the\nmosses and ferns; and among the metazoa in the cnidaria, platodes,\ntunicates, etc. Often the two generations differ considerably in shape\nand degree of organization. Thus, in the mosses the asexual generation\nis the spore-forming moss capsule (_sporogonium_), while the sexual is\nthe moss plant with stalk and leaves (_culmus_). In the case of the\nferns, on the other hand, the latter is spore-forming and monogenetic,\nwhile the thallus-formed, simple, and small fore-germ (_prothallium_)\nis sexually differentiated. In most of the cnidaria a small stationary\npolyp is developed out of the ovum of the free-swimming medusa, and\nthis polyp, in turn, generates by budding medus\u00e6, which reach sexual\nmaturity. In the tunicates (salpa) a sexual social form alternates with\nan asexual solitary form; the chain-salpa of the former are smaller and\ndifferently shaped than the large individual salpa of the latter, which\nagain generate chains by budding. This special form of metagenesis was\nthe first to be observed, as it was in 1819 by the poet Chamisso, when\nhe sailed round the world. In other cases (for instance, in the closely\nrelated _doliolum_) a sexual generation alternates with two (or more)\nneutral ones. The explanation of these various forms of alternating\ngenerations is given in the laws of latent heredity (atavism), division\nof labor, and metamorphosis, and especially by the biogenetic law.\n\nWhile in real metagenesis (alternation of generations in the strict\nsense) the asexual generation propagates by budding or spore-formation,\nthis is done parthenogenetically in the cognate process of\nheterogenesis. This it is which, especially in many of the articulates,\ncauses an immense increase of the species in a short time. Among the\ninsects we have the leaf-lice (aphides), and among the crustacea the\nwater-fleas (daphnides), that propagate in great numbers during warm\nweather by unfertilized \"summer-ova.\" It is not until the autumn that\nmales appear and fertilize the large \"winter-ova\"; in the following\nspring the first parthenogenetic generation issues from the winter\neggs. The two heterogenetic generations are very different in the\nparasitic suctorial worms (trematodes). From the fertilized ovum of the\nhermaphrodite distoma we get simply constructed nurses (p\u00e6dogenetic\nlarv\u00e6), inside which cercaria are generated from unfertilized ova;\nthese travel, and are afterwards converted (inside another animal) into\ndistoma once more.\n\nI have given (_General Morphology_, chap, ii., p. 104) the name of\nstrophogenesis to the complicated process of cell-reproduction,\nwhich we find in the ontogeny of most of the higher histona, both\nphanerogams and c\u0153lomaria. In these there is not a real alternation\nof generations, as the multicellular tissue-forming organism develops\ndirectly from the impregnated ovum. But the process resembles\nmetagenesis in so far as the ontogenetic construction consists itself\nin a repeated division of the cells. Many generations of cells proceed\nby cleavage from the one stem-cell (the impregnated ovum) before two\nof these cells become sexually differentiated, and form a generation\nof sexual cells. However, the essential difference consists in the\nfact that all these generations of cells--in the body of both the\nhigher animals and the flowering plants--remain joined together as\nparts of a single bion (a unified physiological individual); but in\nthe alternation of generations each group produced is made up of a\nnumber of bionta, which live as independent forms--often so different\nfrom each other that they were formerly thought to be animals of\nseparate classes, such as the polyps and medus\u00e6. Hence we must not\ndescribe the reproductive circle of the phanerogams as an alternation\nof generations, although it has started from the fern (by abbreviated\nheredity).\n\nAll simple forms of sexual reproduction without alternation of\ngenerations are comprised under the title of _hypogenesis_. The\ngenerative cycle proceeds from ovum to ovum in one and the same\nbion or physiological individual. This form of development is usual\nwith most of the higher animals and plants; it may proceed with or\nwithout metamorphosis. The younger forms which arise temporarily in\nthe latter case, and are distinguished from the sexually ripe form\nby the possession of the provisional (and subsequently disappearing)\norgans--larva organs (for instance, the tadpole or the pupa), are\ncomprised under the general head of larv\u00e6.\n\nAs a rule, only organisms of the same species seem to have sexual\nunion and generate fertile progeny. This was formerly a rigid dogma,\nand served the purpose of defining the loose idea of the species.\nIt was said: \"When two animals or plants can have fertile offspring\nthey belong to the same real species.\" This principle, which once\nafforded support to the dogma of the constancy of species, has long\nbeen discarded. We now know by numbers of sound experiments that not\nonly two closely related species, but even two species of different\ngenera, may have sexual intercourse in certain circumstances, and that\nthe hybrids thus generated can have fertile offspring, either by union\namong themselves or with one of the parents. However, the disposition\nto hybridism varies considerably, and depends on the unknown laws of\nsexual affinity. This sexual affinity must be based on the chemical\nproperties of the plasm of the copulating cells, but it seems to show\na good deal of vagueness in its effect. As a rule, hybrids exhibit a\ncombination of the features of both parents.\n\nIt has been proved by many recent experiments that hybrids have a more\npowerful build and can reproduce more strongly than pure offspring,\nwhereas pure selection has generally in time an injurious effect. A\nfreshening by the introduction of new blood seems to be good from time\nto time. Hence, it is just the reverse of what the former dogma of the\nconstancy of species affirmed. The question of hybridism has, generally\nspeaking, no value in defining the species. Probably many so-called\n\"true species,\" which have relatively constant features, are really\nonly permanent hybrids. This applies especially to lower sea-dwelling\nanimals, the sexual products of which are poured into the water and\nswarm together in millions. As we know of various species of fishes,\ncrabs, sea-urchins, and vermalia, that their hybrids are very easily\nproduced and maintained by artificial impregnation, there is nothing to\nprevent us from believing that such hybrids are also maintained in the\nnatural state.\n\nThe short survey we have made of the manifold varieties of reproduction\nis sufficient to give an idea of the extraordinary wealth of this world\nof wonders. When we go more closely into details we find hundreds of\nother remarkable variations of the process on which the maintenance\nof the species depends. But the most important point of all is the\nfact that all the different forms of tocogony may be regarded as\nconnected links of a chain. The steps of this long ladder extend\nuninterruptedly from the simple cell-division of the protists to the\nmonogony of the histona, and from this to the complicated amphigony\nof the higher organisms. In the simplest case, the cell-cleavage of\nthe monera, propagation (by simple transverse division) is clearly\nnothing more than transgressive growth. But even the preliminary\nstage of sexual differentiation, the copulation of two equal cells\n(_gameta_), is really nothing but a special form of growth. Then, when\nthe two gameta become unequal in the division of labor, when the larger\ninert macrogameton stores up food in itself, and the smaller, mobile\nmicrogameton swims in search of it, we have already expressed the\ndifference between the female ovum and the male sperm-cell. And in this\nwe have the most essential feature of sexual reproduction.\n\nThe reproduction of the organism is often regarded as a perfect mystery\nof life, and as the vital function which most strikingly separates\nthe living from the lifeless. The error of this dualistic notion is\nclear the moment one impartially considers the whole gradation of\nforms of reproduction, from the simplest cell-division to the most\nelaborate form of sexual generation, in phylogenetic connection. It is\nobvious all through that transgressive growth is the starting-point\nin the formation of new individuals. But the same must be said of\nthe multiplication of inorganic bodies--the cosmic bodies on the\nlarger scale, crystals on the smaller scale. When a rotating sun\npasses a certain limit of growth by the constant accession of falling\nmeteorites, nebulous rings are detached at its equator by centrifugal\nforce, and form into new planets. Every inorganic crystal, too, has\na certain limit of individual growth (determined by its chemical and\nmolecular constitution). However much mother-water you add, this\nis never passed, but new crystals (daughter-crystals) form on the\nmother-crystal. In other words, growing crystals propagate.\n\n\n\n\nXII\n\nMOVEMENT\n\n Mechanics as the science of motion (kinematics and\n phoronomism)--Chemistry of vital movement--Active and passive\n movements--Undulatory movement--Mechanism of imbibition--Autonomous\n and reflex movements--Will and willing--Mixed movements--Movements\n of growth--Direction of the vital movement--Direction of the\n crystallizing force--Direction of cosmic motion--Movements of\n protists--Am\u0153boid, myophenous, hydrostatic, secretory, vibratory\n movements: cilia and lashes--Movements of histona, metaphyta, and\n metazoa--Locomotion of tissue animals: ciliary motion and muscular\n movements--Muscles of the skin--Active and passive organs of\n movement--Radiata, articulata, vertebrata, mammalia--Human movements.\n\n\nAll things in the world are in perpetual motion. The universe is a\n_perpetuum mobile_. There is no real rest anywhere; it is always\nonly apparent or relative. Heat itself, which constantly changes, is\nmerely motion. In the eternal play of cosmic bodies countless suns and\nplanets rush hither and thither in infinite space. In every chemical\ncomposition and decomposition the atoms, or smallest particles of\nmatter, are in motion, and so are the molecules they compose. The\nincessant metabolism of the living substance is associated with a\nconstant movement of its particles, with the building up and decay of\nplasma-molecules. But here we must disregard all these elementary kinds\nof movement, and be content with a brief consideration of those forms\nof motion which are peculiar to organic life, and a comparison of them\nwith the corresponding motions of inorganic bodies.\n\nThe science of motion, or mechanics, is now taken in very different\nsenses: (1) in the widest sense as a philosophy of life [generally\ncalled mechanism or mechanicism in England], equivalent to either\nmonism or materialism; (2) in the stricter sense as the physical\nscience of motion, or of the laws of equilibrium and movement in\nthe whole of nature (organic and inorganic); (3) in the narrowest\nsense as part of physics, or dynamics, the science of moving forces\n(in opposition to statics, the science of equilibrium); (4) in the\npurely mathematical sense as a part of geometry, for the mathematical\ndefinition of magnitudes of movement; and (5) in the biological sense\nas phoronomy, the science of the movements of organisms in space.\nHowever, these definitions are not yet universally adopted, and\nthere is a good deal of confusion. It would be best to follow the\nlead of Johannes M\u00fcller, as we are going to do here, and restrict\nthe name phoronomy to the science of the vital movements which are\npeculiar to organisms, in contrast to kinematics, the exact science\nof the inorganic movements of all bodies. The real material object\nof phoronomy is the plasm, the living matter that forms the material\nsubstratum of all active vital movements.\n\nOn our monistic principles the inner nature of organic life consists in\na chemical process, and this is determined by continuous movements of\nthe plasma-molecules and their constituent atoms. As we have already\nconsidered this metabolism in the tenth chapter, we need do no more\nhere than point out that both the general phenomena of molecular\nplasma-movement and their special direction in the various species of\nplants and animals can be reduced in principle to chemical laws, and\nare subject to the same laws of mechanics as all chemical processes\nin organic and inorganic bodies. In this we emphasize our opposition\nto vitalism, which sees in the _direction_ of plasma-movement the\nsupernatural influence of a mystical vital force or of some ghostly\n\"dominant\" (Reinke). We agree with Ostwald, who also reduces these\ncomplex movements to the play of energy in the plasm--that is to say,\nin the last instance to modifications of chemical energy. In regard to\nthe visible movements of the living things which concern us at present,\nwe must first distinguish passive and active, and subdivide the latter\ninto reflex and autonomous.\n\nMany movements of the living organism which the inexpert are inclined\nto attribute to life itself are purely passive; they are due either to\nexternal causes which do not proceed from the living plasm, or to the\nphysical composition of the organic but no longer living substance.\nPurely passive movements, which play an important part in bionomy and\nchorology, comprise such as the flow of water and the rush of the wind;\nthey cause considerable changes of locality and \"passive\" migrations\nof animals and plants. Purely physical, again, is what is known as the\nBrownian molecular movement which we observe with a powerful microscope\nin the plasm of both dead and living cells. When very fine granules\n(for instance, of ground charcoal) are equally distributed in a liquid\nof a certain consistency, they are found to be in a constant shaking or\ndancing movement. This movement of the solid particles is passive, and\nis due to the shocks of the invisible molecules of the fluid which are\ncontinually impinging upon each other. In the rhizopods--the remarkable\nprotozoa whose unicellular organism sheds so much light on the obscure\nwonders of life--we notice a curious streaming of the granules in\nthe living plasm. Within the cytoplasm of the am\u0153b\u00e6 particles\ntravel up and down in all directions. On the long thin plasma-threads\nor pseudopodia which stream out from the unicellular body of the\nradiolaria and thalamophora, thousands of fine particles move about,\nlike promenaders in a street. This movement does not come from the\npassive granules, but from the active invisible molecules of the\nplasm, which are always changing their relative positions. Thus also\nthe movements of the blood-cells which we can see with the microscope\nin the circulation of a young transparent fish, or in the tail of a\nfrog-larva, are not due to the action of the blood-cells themselves,\nbut to the flow of the blood caused by the beat of the heart.\n\nAn important factor in the life of many organisms, especially the\nhigher plants, is the physical phenomenon called _imbibition_; it\nconsists in the penetration of water between the molecules of solid\nbodies (drawn to them by molecular attraction), and the consequent\ndisplacement of the molecules by the fluid. In this way the volume of\nthe solid body is increased, and movements are produced which may have\nthe appearance of vital processes. The energy of these imbibitional\nbodies is notoriously very powerful; we can, for instance, split large\nblocks of stone by the insertion of a piece of wood dipped in water. As\nthe cellulose membrane of plant-cells has this property of imbibition\nin a high degree (either in the living or the dead cell), the movements\nit causes are of great physiological importance. This is especially\nthe case when the imbibition of the cell wall is one-sided, and causes\na bending of the cell. In consequence of the unequal strain in the\ndrying of many fruits, they split open and project their seeds to some\ndistance (as do the poppy, snap-dragon, etc.). The moss-capsules also\nempty their spores as a result of imbibition-curving (in the teeth\nof the openings of the spore-cases). The hygroscopic points of the\nheron-bill (_erodium_) curl up in the dry state and stretch out when\nmoist; hence they are used as hygrometers in the construction of\nmeteorological huts. The so-called \"resurrection plants\" (_anastatica_,\nthe rose of Jericho, and _selaginella lepidophylla_), which close up\nlike a fist when dry, spread their leaves out flat when moistened (the\nleaves imbibing strongly on the inner side). There is no more real\ncase of \"resuscitation\" (as many believe) in these cases than in the\nmythological resurrection of the body. However, these phenomena of\nimbibition are not active vital processes; they are independent of the\nliving plasm, and due solely to the physical constitution of the dead\ncell-membranes.\n\nIn contrast with these passive movements of organisms, we have\nthe active movements which proceed from the living plasm. In the\nultimate analysis, it is true, these may be reduced to the action of\nphysical laws just as well as the passive movements. But the causes\nof them are not so clear and obvious; they are connected with the\ncomplicated chemical molecular processes of the living plasm, of the\nphysical regularity of which we are now fully convinced, though their\ncomplicated mechanism is not yet understood. We may divide into two\ngroups the many different movements, which are called vital in this\nstricter sense, and were formerly regarded as evidences of the presence\nof a mystic vital force, according as the stimulus--the sensation of\nwhich is caused by the movement--is directly perceptible or not. In\nthe first case, we have stimulated (or reflex or paratonic) movements,\nand in the second voluntary (autonomous or spontaneous) movements. As\nthe will appears to be free in the latter, they have been left out of\nconsideration by many physiologists, and handed over to the treatment\nof the metaphysical psychologist. On our monistic principles this is a\ngrave error; nor is it improved when \"psychonomism\" appeals to a false\ntheory of knowledge. On the contrary, the conscious will (and conscious\nsensation) is itself a physical and chemical process like unconscious\nand involuntary movement (and unconscious feeling). They are both\nequally subject to the law of substance. However, only the external\nstimuli which cause reflex movements are known to us to any great\nextent and experimentally recognizable; the internal stimuli, which\naffect the will, are mostly unknown, and are not directly accessible\nto investigation. They are determined by the complicated structure of\nthe psychoplasm, which has been gradually acquired by phylogenetic\nprocesses in the course of millions of years.\n\nThe great problem of the will and its freedom--the seventh and last\nof Dubois-Reymond's world-riddles--has been dealt with fully in the\n_Riddle_ (chapter vii.). But as we still meet with the most glaring\ncontradictions and confusion in regard to this difficult psychological\nquestion, I must touch upon it briefly once more. In the first place, I\nwould remind the reader that it is best to restrict the name \"will\" to\nthe purposive and conscious movements in the central nervous system of\nman and the higher animals, and to give the name of impulses (tropisms)\nto the corresponding unconscious processes in the psychoplasm of the\nlower animals, as well as of the plants and protists. For it is only\nthe complicated mechanism of the advanced brain structure in the higher\nanimals, in conjunction with the differentiated sense-organs on the one\nside and the muscles on the other, that accomplishes the purposive and\ndeliberate actions which we are accustomed to call acts of will.\n\nBut the distinction between voluntary (autonomous) and involuntary\n(reflex) movements is as difficult to carry out in practice as it is\nclear in theory. We can easily see that the two forms of movement\npass into each other without any sharp boundary (like conscious and\nunconscious sensation). The same action, which seems at first a\nconscious act of the will (for instance, in walking, speaking, etc.),\nmay be repeated the next moment as an unconscious reflex action. Again,\nthere are many important mixed or instinctive movements, the impulse to\nwhich comes partly from internal and partly from external stimuli. To\nthis class belong especially the movements of growth.\n\nEvery natural body that grows increases its extent, fills a larger\npart of space, and so causes certain movements of its particles; this\nis equally true of inorganic crystals and the living organism. But\nthere are important differences between the growth in the two cases.\nIn the first place, crystals grow by the external apposition of fresh\nmatter, while cells grow by the intussusception of fresh particles\nwithin the plasm (_cf._ chapter x.). In the second case, in growth,\nwhich determines the whole shape of the organism, two important factors\nalways co-operate, the inner stimulus, which depends on the specific\nchemical constitution of the species, and is transmitted by heredity,\nand the external stimulus which is due to the direct action of light,\nheat, gravity, and other physical conditions of the environment, and is\ndetermined by adaptation (phototaxis, thermotaxis, geotropism, etc.).\n\nA peculiar property of many vital movements (but by no means all)\nis the definite direction they exhibit; these are generally called\npurposive movements. For the teleologist they afford one of the chief\nand most welcome proofs of the dualistic theory of the older and the\nmodern vitalism. Baer, especially, has laid stress on the purposiveness\nof all vital movement. It has been given a more precise expression\nrecently by Reinke. His \"dominants\" are \"intelligent directive\nforces,\" essentially different from all forms of energy or natural\nforces, and not subject to the law of substance. These metaphysical\n\"vital spirits\" are much the same as the immortal soul of dualistic\npsychology or the divine emanations of ancient theosophy. They are\nsupposed not only to regulate the special development and construction\nof every species of animal and plant, and direct it to a predetermined\nend, but also to control all the various movements of the organism\nand its organs down to the cells. These \"hyperenergetic forces\" are\nequivalent to the \"organizing principle\" and the \"unconscious will\"\nof Edward Hartmann, the \"arranging and controlling protoplasmic\nforces\" of Hanstein and others. All these metaphysical, supernatural,\nand teleological ideas, like the older mystic notion of a special\nvital force, rest on a perversion of judgment by the apparent freedom\nof will and purposiveness of organization in the higher organisms.\nThese thinkers overlook the fact that this purposiveness can be\ntraced phylogenetically to simple physical movements in the lower\norganisms. Moreover, they overlook or deny the definite direction of\ninorganic forms of energy, though this is just as clear in the origin\nof a crystal as in the composition of the whole world-structure, in\nthe direction of the mind as in the orbit of a planet. Hence it is\nimportant to bear in mind always these two forms of mechanical energy,\nand emphasize their identity with the direction of vital movement.\n\nThe force of gravitation which is at work in crystal-formation in\nthe simple chemical body exhibits just as definite a direction as\nthat which appears in the plasm in cell-construction. In this and\nother respects the comparison of the cell with the crystal, which was\nmade even by the founders of the cell-theory, Schleiden and Schwann,\nin 1838, is thoroughly justified, though it is not correct in some\nother aspects. When the crystal is formed in the mother-water, the\nhomogeneous particles of the chemical substance arrange themselves\nin a perfectly definite direction and order, so that mathematical\nplanes of symmetry and axes arise within, and definite angles at the\nsurface. On the strength of this, modern crystallography distinguishes\nsix different systems of crystals. But, in different conditions, the\nsame substance may crystallize in two or even three different systems\n(dimorphism and trimorphism of the crystal); thus, for instance,\ncarbonate of lime crystallizes as calcspar in the hexagonal, and as\narragonite in the rhombic system. If Reinke would be consistent, he\nought to postulate a \"dominant\" for every crystal, to control the order\nand direction of the particles in its formation. He makes the curious\nstatement (in 1899) that direction \"is not a measurable magnitude\" like\nenergy, and so is not subject, like it, to the law of substance. We can\nmathematically determine the direction of the constructive force in the\ncrystal just as well as in the cell.\n\nIf we comprise under the head of cosmokinesis the whole of the\nmovements of the heavenly bodies in space, we cannot deny that they\nhave a definite direction in detail, although our knowledge of this is\nstill very incomplete. We can calculate the distances and speeds and\nmovements of the planets round the sun with mathematical accuracy; and\nwe gather from our astronomical observations and calculations that a\nsimilar regularity prevails in the movements of the other countless\nbodies in infinite space. But we do not know either the first impulse\nto these complex movements or their final goal. We can only conclude\nfrom the great discoveries of modern physics, supported by spectrum\nanalysis and celestial photography, that the universal law of substance\non the one side and the law of evolution on the other control the\ngigantic movements of the heavenly bodies just as they do the living\nswarm of tiny organisms that have inhabited our little planet for\nmillions of years. Reinke ought, consistently, to admire the cosmic\nintelligence of the Supreme Being in these movements of the cosmic\nmasses and its emanations, the \"dominants,\" in the actual direction\nof their movements, as much as he does in the plasma-flow in the tiny\norganism.\n\nThe manifold gradation of vital movement which we find everywhere in\nthe higher organisms is not without expression even in the protist\nrealm. In this respect the chromacea, the simplest forms of vegetal\nmonera, and the bacteria, which we regard as corresponding animal\nforms, developed from the former by metasitism, are of great interest.\nAs microscopic scrutiny fails to detect any purposive organization in\nthese unnucleated cells, and it is impossible to discover different\norgans in their homogeneous plasma-body, we have to look upon their\nmovements as direct effects of their chemical molecular structure. But\nthe same must be said also of a number of nucleated cells, both among\nthe protophyta and the protozoa; only in this case the structure is\nless simple, in so far as both the nucleus itself and the surrounding\ncell-body exhibit, in indirect division, complicated movements in the\nplasm (caryokinesis). Apart from these, however, there is nothing to\nbe seen in many unicellular beings (_e.g._, paulotomea, or calcocytea)\nthat we need call \"vital movement.\" On the border between the organic\nand inorganic worlds we have, as regards movement, the simplest forms\nof the chromacea, chroococcacea. We can see no vital movement in\nthese structureless particles of plasm except slight changes of form,\nwhich occur when they multiply by cleavage. The internal molecular\nmovements of the living matter, which effect their simple plasmodomous\nmetabolism and growth, lie beyond our vision. The reproduction itself,\nin its simplest form of self-cleavage, seems to be merely a redundant\ngrowth, exceeding the limit of individual size for the homogeneous\nplasma-globule (_cf._ chapters ix. and x.).\n\nThe great majority of the protists have the appearance of real,\nnucleated cells. Hence we have to distinguish two different forms\nof movement in the unicellular organism--the inner movement in the\ncaryoplasm of the nucleus and the outer in the cytoplasm of the\ncell-body; the two enter into close mutual relations during the\nremarkable process of partial resolution of the nucleus (caryolysis).\nIn this modification and partial dissolution of their constituents we\nobserve, during indirect cell-division, certain complicated movements\n(the significance of which is as yet entirely unknown), that are\naccomplished by both the granules of chromatin and the threads of\nachromin, and which are comprised under the head of nuclear movements\n(caryokinesis). It has lately been attempted to explain them on purely\nphysical principles. The same may be said of the internal flow of the\nplasm which we find in the plasmodia of the am\u0153b\u00e6 and mycetozoa, and\nin the endoplasm of many of the protophyta and protozoa.\n\nThe slow displacement of the molecules of plasm which is at the\nbottom of these plasma-movements also causes a variety of external\nchanges of form in simple naked cells. Variable processes like folds\nor fingers (the \"fold-feet,\" _lobopodia_) appear on their surface. As\nthey are best observed in the common am\u0153b\u00e6 (naked nucleated cells\nof the simplest kind), they are called am\u0153boid movements. With\nthese is connected the variable movement of the larger rhizopods, the\nradiolaria and thalamophora, in which hundreds of fine threads radiate\nfrom the surface of the naked plasma-body. A number of recent experts\non the rhizopods, such as B\u00fctschli, Richard Hertwig, Rhumbler, and\nothers, have attempted to trace to purely physical causes this varying\nformation of pseudopodia, and their branching and net-like structure\n(without definite direction).\n\nIt is more difficult to do this in the case of the most highly\ndifferentiated of the protozoa, the infusoria. With these the free\nmovement of the unicellular protozoon is farther advanced through\nthe formation of permanent hairlike processes (long single lashes in\nthe flagellata, and a number of short lashes in the ciliata) on the\ncell-surface and the movement of these by contraction and expansion,\nlike the limbs, tentacles, and bones of the higher animals. The\napparent spontaneity and various modulation in the ever-changing\nmovements of these cell-feet is, in many of the infusoria, so like the\nautonomous voluntary movements in the metazoa that several experts on\nthe infusoria have been moved on this account to ascribe individual\n(and even conscious) souls to them. Hence the difference between the\nvarious kinds of living movement is already very considerable before\nwe leave the kingdom of the protists. On the one hand, the lowest\nmonera (chromacea) join on directly to inorganic phenomena. On the\nother hand, the highly differentiated infusoria (ciliata) show so\ngreat a resemblance to the higher animals in their differentiated and\nautonomous movements that they have been credited with the possession\nof \"free-will.\" There is no such thing as a sharp division.\n\nIn a large section of the higher protozoa differentiated organs of\nmovement are developed, which may be compared to the muscles of the\nmetazoa. In the cytoplasm threadlike, contractile structures are\nformed, and these have, like the muscular fibres of the metazoa, the\npower to contract and expand again in definite directions. These\nmyoph\u00e6na or myonema form, in many of the infusoria, both ciliata\nand flagellata, a special thin layer of parallel or crossed fibres\nunderneath the exoplasm or the hyaline skin-layer of the cell. The\nmetabolic body of the infusorium may be altered in various ways by the\nautonomous contraction of these. Special instances of these myoph\u00e6na\nare the _myophrisca_ of the acantharia--contractile threads which\nsurround the radial needles of these radiolaria like a crown. They\nare found in their outer gelatine envelope, the calymma, and by their\ncontraction extend it, and so lessen the specific gravity.\n\nMany of the aquatic protophyta and protozoa have the power of\nautonomous and independent locomotion, and this often has the\nappearance of being voluntary. Among the simplest fresh-water\nprotozoa are the arcellina or thecolobosa (_difflugia_, _arcella_),\nlittle rhizopods that are distinguished from the naked am\u0153b\u00e6 by\nthe possession of a firm envelope. They usually creep about in the\nslime at the bottom, but in certain circumstances rise to the surface\nof the water. As Wilhelm Engelmann has shown, they accomplish this\nhydrostatic movement by means of a small vesicle of carbonic acid,\nwhich expands their unicellular body like an air-balloon; the specific\nweight of the cell-body, which is of itself heavier than water, is\nsufficiently lowered by this. The same method is followed by the pretty\nradiolaria which live floating (as plankton) at various depths of the\nsea. Their unicellular (originally globular) body is divided by a\nmembrane into a firm inner central capsule and a soft outer gelatine\ncovering. The latter, known as the calymma, is traversed by a number\nof water-vesicles or vacuoles. As a result of an osmotic process,\ncarbonic acid may be secreted or pure water (without the salt of the\nsea-water) be imbibed in these vacuoles; by this means the specific\ngravity of the cell is lessened, and it rises to the surface. When\nit desires to make itself heavier and sink, the vacuoles discharge\ntheir lighter contents. These hydrostatic movements of the radiolaria\n(for which the myophrisca, still more complicated structures, have\nbeen developed in the acantharia) attain by simple means the same end\nthat is accomplished in the siphonophora and fishes by air-filled and\nvoluntarily contractile swimming-bladders.\n\nNumbers of the unicellulars alter their position very\ncharacteristically by secreting a thick mucus at one side of their body\nand fastening this to the ground. If the secretion continues, a longish\njelly-like stalk is produced by which the cell slowly pushes itself\nalong, like a boat with a rowing-pole. This secretory locomotion is\nfound, among the protophyta, in the desmidiacea and diatomes, and in\nsome of the gregarin\u00e6 and rhizopods among the protozoa. The peculiar\nrolling movements of the oscillaria (threadlike chains of blueish-green\nunnucleated cells, closely related to the chromacea) are also effected\nby the secretion of mucus. On the other hand, it is probable that the\nsliding movements of many of the diatomes are due to fine processes\n(vibratory hairs?) in the plasm, which proceed either out of the seams\n(_raphe_) of the bivalvular silicious shells or through the fine pores\nin them.\n\nEspecially important in the easy and rapid locomotion of many\nunicellulars is the formation of fine hairlike processes at the surface\nof the body; in the broadest sense, they are called vibratory hairs.\nIf only a few whiplike threads are formed, they are called _whips_\n(_flagella_); if many short ones, _lashes_ (_cilia_). Flagelliform\nmovement is found in some of the bacteria, but especially in the\nmastigophorous \"whip-infusoria,\" in the mastigota among the protophyta,\nand the flagellata among the protozoa. As a rule, we have in these\ncases one or two (rarely more) long and very thin whip-shaped\nprocesses, starting from one pole of the long axis of the oval, round,\nor long cell-body. These whips (_flagella_) are set in vibratory motion\n(apparently often voluntary) in various ways, and serve not only for\nswimming or creeping, but also for feeling and securing food. Similar\nwhip-cells (_cellul\u00e6 flagellat\u00e6_) are also found very commonly in the\nbody of tissue-animals, usually packed together in an extensive layer\nat the inner or outer surface (ciliated epithelium). If single cells\nare released from the group, they may live independently for some time,\ncontinuing their movements and resembling free infusoria. The same may\nbe said of the travelling spores of many of the alg\u00e6, and of the most\nremarkable of all ciliated cells--the spermia or spermatozoa of plants\nand animals.\n\nAs a rule they are cone-shaped, having an oval or pear-shaped (though\noften also rod-shaped) head, which tapers into a long and thin thread.\nWhen their lively movements were first noticed in the male seminal\nfluid (each drop of which contains millions of them) two hundred years\nago, they were thought to be real independent animalcules, like the\ninfusoria, and so obtained their name of seed-animals (spermatozoa).\nIt was a long time (sixty years ago) before we learned that they are\ndetached glandular cells, which have the function of fertilizing the\novum. It was discovered at the same time that similar vibratory cells\nare found in many of the plants (alg\u00e6, mosses, and ferns). Many of the\nlatter (for instance, the spermatozoids of the cycadea) have, instead\nof a few long whips, a number of short lashes (_cilia_), and resemble\nthe more highly developed ciliated infusoria (_ciliata_).\n\nThe ciliary movement of the infusoria is held to be a more perfect form\nof vibratory movement, because the many short lashes found on them are\nused for different purposes, and have accordingly assumed different\nforms in the division of labor. Some of the cilia are used for running\nor swimming, others for grasping or touching, and so on. In social\ncombinations we have the ciliated cells of the ciliated epithelium of\nthe higher animals--for instance, in the lungs, nostrils, and oviducts\nof vertebrates.\n\nIn the unicellular, non-tissue forming protists, all the vital\nmovements seem to be active functions of the plasm of the single\ncell; but in the histona, the multicellular tissue-forming organisms,\nthey are the outcome of the combined movements of the many cells\nwhich compose the tissue. Careful anatomic study and experimental\nphysiological scrutiny of the motor processes are, therefore, first\ndirected, in the case of the histona, to clearing up the nature and\nactivity of the special cells which compose the tissue, and then the\nstructure and functions of the tissue itself. When we start from this\npoint, and survey the manifold active motor phenomena of the histona\nas a whole, we see at once an essential agreement in the phoronomy of\nthe two kingdoms of the metaphyta and metazoa, in the sense that at the\nlower stages the chemical and physical character of the motor processes\ncan be clearly shown and can be traced to an interchange of energy in\nthe plasm of the cells that make up the tissue. In the higher stages,\nhowever, we find striking differences, the voluntary character of many\nautonomous movements being very conspicuous in the higher animals,\nand thus the great problem of the freedom of the will is added to the\npurely physiological questions of stimulated movement, growth-movement,\netc.\n\nMoreover, the movements of the metazoa are much more varied and\ncomplicated than those of the metaphyta, in consequence of the higher\ndifferentiation of their sense-organs and the centralization of their\nnervous system. The former have generally free locomotion and the\nlatter not. The special mechanism of the organs of movement is also\nvery different in the two groups. In most of the metazoa the chief\nmotor organs are the muscles, which have developed in the highest\ndegree the power of definitely directed contraction and expansion.\nIn most of the metaphyta, on the other hand, the chief part of the\nmovements depend on the strain of the living plasm, or what is called\nthe _turgor_ or expansibility of the plant-cells. This is effected\nby the osmotic pressure of the internal cell-fluid and the elasticity\nof the cellulose wall, which is thus expanded. Nevertheless, in both\ncases--and in all \"vital\" phenomena--the real cause of the process is,\nin the ultimate analysis, the chemical play of energy in the active\nplasm.\n\nThe metaphyta, with few exceptions, are fixed in one spot for life, or\nonly mobile for a short time when they are young. In this they resemble\nthe lower metazoa, the sponges, polyps, corals, bryozoa, etc. They have\nnot free locomotion. The motor phenomena which we find in them affect\nonly special parts or organs. They are mostly reflex or paratonic,\nand due to external stimuli. Only a few of the higher plants exhibit\nautonomous or spontaneous movement, the stimulating cause of which is\nunknown to us, and which may be compared to the apparently voluntary\nactions of the higher animals. The lateral feather-leaves of an Indian\nbutterfly flower (_hedysarum gyrans_) move in circles through the air,\nlike a pair of arms swinging, without any external cause; they complete\na circle in a couple of minutes. Variations in the intensity of light\nhave no effect on them. Similar spontaneous movements of the leaves\nof several species of clover (_trifolium_) and sorrel (_oxalis_) are\nperformed only in the dark, not in the light. The terminal leaf of\nthe meadow-clover repeats its rotation, which describes more than one\nhundred and twenty degrees of an arc, every two to four hours. The\nmechanical cause of these spontaneous \"variation movements\" seems to\nlie in variations of expansibility.\n\nVoluntary and autonomous turgescence-movements of this kind are only\nobserved in a few of the higher plants, but stimulated movements that\nare accomplished by the same mechanism are very common in the vegetal\nworld. We have, especially, the well-known \"sleep,\" or nyktitropic\nmovements, of many plants. Many leaves and flowers hold themselves\nvertically to the streaming rays of the sun. When darkness comes on\nthey contract, and the calices of the flowers close. Many flowers are\nopen for only a few hours a day. The mechanism of turgescence, which\neffects these swelling movements, consists in the co-operation of the\nosmotic pressure of the internal cell-fluid and the elasticity of the\nstrained cell-membrane enclosing the cytoplasm. The strain of the outer\ncellulose membrane on the plasmatic primordial sac within it grows so\nmuch on the accession of osmotically active matter that the internal\npressure is equal to several atmospheres, and the elastic strained\nmembrane stretches from ten to twenty percent. When water is withdrawn\nagain from one of these swollen or turgescent cells, the membrane\ncontracts; the cell becomes smaller, and the tissue looser. Other\nstimuli besides light (heat, pressure, electricity) may produce these\nexpansional variations, and, as a consequence of it, certain reflex\nmovements (or paratonic variational movements). The most striking and\nfamiliar examples are the flesh-eating fly-trap (_dion\u00e6a muscipula_)\nand the sensitive plant (_mimosa pudica_); their contraction is caused\nby mechanical stimuli, shaking, pressure, or the touching of the leaves.\n\nMost of the higher animals have the power of free and voluntary\nlocomotion. It is, however, wanting in some of the lower classes,\nwhich spend the greater part of their life at the bottom of the water,\nlike plants. Hence these were formerly held to be vegetable--thus\nthe sponges, polyps, and corals among the c\u0153lenteria. A number\nof classes of the c\u0153lomaria have also adopted the stationary\nlife, such as the bryozoa and the spirobranchia among the vermalia,\nmany mussels (oysters, etc.), the actinia among the tunicates, the\nsea-lilies (_crinoidea_) among the echinoderms, and even highly\norganized articulate, such as the tube-worms (_tubicol\u00e6_), among the\nannelids, and the crawling crabs (_cirripedia_), among the crustacea.\nAll these stationary metazoa move freely in their youth, and swim about\nin the water as _gastrul\u00e6_, or in some other larva form. They have\ntaken only gradually to stationary habits, and have been considerably\nmodified, and often greatly degenerated, in consequence; for instance,\nin the loss of the higher sense-organs, the bones, and even of the\nwhole head. Arnold Lang has shown this very clearly in his excellent\nwork on the influence of stationary life on animals. The study of\nthese retrogressive metamorphoses is very important for the theory of\nprogressive heredity and selection; it also shows the great value of\nfree locomotion for the higher sensitive and intellectual development\nof the animals and man.\n\nIn many of the lower aquatic metazoa the surface of the body is covered\nwith vibratory epithelium--that is to say, with a layer of skin-cells\nwhich bear either one long whip (_flagellum_) or several short lashes\n(cilia). Flagellated epithelium is especially found in the cnidaria\nand platodes; ciliated epithelium mostly in the vermalia and mollusca.\nAs the lashing motion of these hairlike processes brings a constant\nstream of fresh water to the surface of the body, they first of all\neffect respiration through the skin. But in many of the smaller metazoa\nthey also serve the purpose of locomotion, as in the gastr\u00e6ads,\nthe turbellaria, the rotifera, the nemertina, and the young larv\u00e6\nof many other metazoa. The vibratory apparatus reaches its highest\ndevelopment in the _ctenophora_. The extremely delicate and soft body\nof these gherkin-shaped cnidaria swims slowly in the water by means\nof the strokes of thousands of tiny oar-blades. They are arranged in\neight longitudinal rows which stretch from the mouth to the opposite\npole. Each oar-blade consists of the long hair-lashes of a group of\nepithelial cells glued together.\n\nThe chief motor organs in the metazoa are the muscles which constitute\nthe \"flesh\" of the body. Muscular tissue consists of contractile\ncells--that is to say, of cells with the sole property of contraction.\nWhen the muscular cell contracts, it becomes shorter and its diameter\nincreases. This brings nearer together the two parts of the body to\nwhich its ends are attached. In the lower metazoa the muscle-cells\nhave, as a rule, no particular structure; but in the higher animals the\ncontractile plasm undergoes a peculiar differentiation, which has the\nappearance under the microscope of a transverse streaking of the long\ncells. On this ground a distinction is drawn between striated muscles\nand simple non-striated or smooth muscles. The more vigorous, rapid,\nand definite is the contraction of the muscle, the more marked is the\nstreaky character, and the more pronounced the difference between the\ndoubly refractive muscular particles from the simple refractive. The\nstriated muscle is \"the most perfect dynamo we know of\" (Verworn). The\nnormal heart of a man accomplishes every day, according to Zuntz, a\nwork of about twenty thousand kilogrammetres--in other words, an energy\nthat would suffice to lift to a height of one metre a weight of twenty\nthousand kilogrammes. In many flying insects (gnats, for instance) the\nflying muscles make three hundred to four hundred contractions a second.\n\nIn the lower and higher classes of the metazoa the muscle amounts to\nno more than a thin layer of flesh underneath the skin. This layer\nconsists of muscular cells, which come originally from the ectoderm\nin the form of internal contractile processes of the skin-cells\nthemselves, as in the polyps. In other cases the muscle-cells are\ndeveloped from the connective-tissue cells of the mesoderm, the\nmiddle skin-layer, as in the ctenophora. This mesenchymic muscle is\nless common than epithelial muscle. In most of the askeletal vermalia\nthe subdermal muscle divides into two layers--an outer deposit of\nconcentric muscles and an inner layer of longitudinal muscles; in the\ncylindrical worms (nematodes, sagitt\u00e6, etc.) the latter fall into\nfour longitudinal bands, one pair of upper (dorsal) and a pair of\nlower (ventral) muscular bands. At those parts of the body which are\nespecially used for locomotion the muscle is more strongly developed,\nas in the belly-side of the crawling worms and mollusks. This muscular\nsurface develops into a kind of fleshy \"foot\" (_podium_); it assumes\na great variety of forms in the various classes of mollusks. In most\nof the snails which creep on the solid ground it grows into a muscular\n\"flat-foot\" (_gasteropoda_); in the mussels which cut like a plough\nthrough the soft slime it forms a sharp \"hatchet-foot\" (_pelecypoda_).\nThe keel-snails (_heteropoda_) swim by means of a \"keel-foot,\" which\nworks like the screw of a ship; the floating-snails (_pteropoda_) swim\nunsteadily (like butterflies flying) by means of a pair of head-folds,\nwhich develop from the side of the anterior foot-section. In the\nhighest mollusks, the cuttle-fishes (_cephalopoda_), this fore-foot\ndivides into four or five pairs of folds, which grow into long and very\nmuscular \"head-arms\"; the numbers of strong suckers on the latter have\nalso special muscles. In all these non-articulate mollusks and vermalia\nhard skeletons are either altogether wanting or (like the external\nshells of the mollusks) they have no functional relation to the motor\nmuscles. It is otherwise in the higher animals, in which we find this\nrelation to a solid jointed skeleton that becomes a passive motor\napparatus.\n\nThe higher groups of the animal kingdom in which a characteristic solid\nskeleton is developed and forms an important starting-point for the\nmuscles, as well as a support and protection for the whole body, are\nthe three stems of the echinoderms, articulates, and vertebrates.\nAll three groups are very rich in forms, and far surpass all the\nother stems of the animal world in the perfection of their locomotive\napparatus. However, the disposition and development of the skeleton as\na passive support, and the correlation of the muscles to it as active\npulling-organs, differ very much in the three classes, and are the\nchief factors in determining their characteristic types; they show\nclearly (even apart from other radical differences) that the three\nstems have arisen independently of each other from three different\nroots in the vermalia-stem. In the echinoderms the calcareous skeleton\nis formed from chalky deposits in the corium, in the articulates from\nchitine secretions of the epidermis, and in the vertebrates from\ncartilage of an internal chord-sheath (_cf._ _Anthropogeny_, chapter\nxxvi.).\n\nThe remarkable stem of the sea-dwelling echinoderms or \"prickly skins\"\nis distinguished from all the other animal groups by a number of\nstriking peculiarities; prominent among these are the special formation\nof their active and passive motor organs and the curious form of their\nindividual development. In this ontogenesis two totally different\nforms appear successively--the simple astrolarva and the elaborately\norganized and sexually mature astrozoon. The small, free-swimming\nastrolarva has the general structural features of the rotatoria, and\nso shows, in accordance with the biogenetic law, that the original\nstem-form of the echinoderms (the amphoridea) belonged to this group\nof the vermalia. I have briefly explained these structures in the\n_History of Creation_ (chapter xxii.), and more fully in my essay on\nthe amphoridea and cystoidea (1896). The little astrolarva has no\nmuscles, and no water-vessels or blood-vessels. It moves by means\nof vibratory lashes or bands, which are attached to special armlike\nprocesses at the surface. These arms are regularly developed to the\nright and left of the bilateral symmetrical larva (which as yet shows\nno trace of the five-rayed structure). By a very curious modification\nthe small bilateral astrolarva is transformed into the totally\ndifferent pentaradial astrozoon, the large sexually mature echinoderm\nwith a pronounced five-rayed structure. (See _Art-forms in Nature_,\nplates 10, 20, 30, 40, 60, 70, 80, 90, and 95.) It has a most elaborate\norganization, with muscles and cuticular skeleton, blood-vessels and\nwater-vessels, etc. A section of the astrozoa--the living crinoidea,\nor sea-lilies, and the extinct classes of blastoidea (sea-buds),\ncystoidea (sea-apples), and amphoridea (sea-urns)--grow in stationary\nfashion at the bottom of the sea. The other four extant classes\ncreep about in the sea--the sea-gherkins (holothuria), the star-fish\n(asteridea and ophoidea), and the sea-urchins (echinidea). Their\ncreeping motion is accomplished by two kinds of organs--water-feet\nand skin-muscles. The latter find their support and attachment in\nsolid calcareous needles, which develop from chalky deposits in the\ncorium. As these calcareous needles (which are particularly conspicuous\nin the sea-urchin) are set movably in special protuberances of the\ncalcareous plates of the cuticular skeleton, and moved by little\nmuscular needles, the echinoderms walk on them as if they were stilts.\nBetween these, however, a number of water-feet arise from inside--thin\ntubes like the fingers of a glove, which are filled with water by\nan internal conduit-system (the so-called ambulacral system) and\nbecome stiff. These very extensible ambulacral feet, often provided\nwith a suctorial plate at the closed outer end, serve for creeping,\nsucking, touching, and grasping. As these distinctive motor organs\nof the echinoderms--both the ambulacral feet with their complicated\nwater-tubes and the movable needles with their joints and muscles--are\nfound in hundreds, often in thousands, on every individual five-rayed\nastrozoon, we might say that the echinoderms have the most advanced\nand complicated motor organs of all animals. Their historical\ndevelopment is perfectly understood from its earliest stages, since\nRichard Semon found, in his ingenious pentact \u00e6atheory (1888),\nthe correct phylogenetic meaning of the curious embryology of the\nechinoderms discovered in 1845 by Johannes M\u00fcller. I endeavored in 1896\nto establish it in detail, in relation to paleontological discoveries,\nin the essay I have mentioned.\n\nThe large stem of the articulata (the richest in forms of all the\nanimal stems) comprises three chief classes--the annelids, crustacea,\nand tracheata. All three groups agree in the essential features\nof their organization, especially in the external articulation or\nmetamerism of the long bilateral body, and also in the repetition of\nthe internal organs in each joint or segment. In each joint there is\noriginally a knot of the ventral nervous system (the ventral marrow), a\nchamber of the dorsal heart, a chitine-ring of the cutaneous skeleton,\nand a corresponding group of muscles.\n\nOf the three great classes of the articulates the annelids are\ndeveloped directly from the vermalia, of which both the nematoda and\nnemertin\u00e6 approach very closely to them. The two other and more highly\norganized classes, the crustacea and tracheata, are younger groups,\nindependently evolved from two different stems of the annelids. The\nannelids, or \"ringed-worms\" (to which, _e.g._, the rain-worms belong),\nhave mostly a very homogeneous articulation; their segments or metamera\nrepeat the same structure to a great extent, especially the subdermal\nmuscles. In a transverse section we see in every joint underneath the\nlayer of concentric muscles a pair of dorsal and a pair of ventral\nmuscles. Their epidermis has secreted a thin covering of chitine, in\nthe tubular worms a leather-like or calcified tube. There are no bones\nin the oldest annelids; in the younger bristle-worms (_polych\u00e6ta_) one\nor two pairs of short unjointed feet (_parapodia_) are found in every\njoint.\n\nThe other two chief classes of the articulates develop long and jointed\nfeet of very varied forms, and at the same time assume different shapes\nof limbs in the division of labor. This heterogeneous articulation\n(heteronomy) is the more pronounced the higher the whole organization.\nThis is equally true of the aquatic, gill-breathing crustacea (crabs,\netc.) and the tracheata (terrestrial animals breathing through a\ntrachea, the myriopods, spiders, and insects). In the higher groups of\nboth classes the number of limbs is usually not higher than fifteen to\ntwenty; and they are distributed in three principal sections--head,\nbreast, and posterior part of the body. The firm covering of chitine,\nwhich was delicate and thin in most of the annelids, is much thicker in\nmost of the crustacea and tracheata, and often hardened by a calcareous\ndeposit; it forms a solid ring of chitine in each segment, inside which\nthe motor muscles are attached. The successive hard rings are connected\nby thin, mobile, intermediate rings, so that the whole body combines\nfirmness, elasticity, and mobility in a high degree. The structure of\nthe long jointed legs, which are fixed in pairs on each segment, is\nvery similar. Hence the typical character of the motor organs of the\ncrustacea lies in the circumstance that both in the body and the limbs\nthe muscles are attached to the interior of hollow chitine tubes, and\ngo in these from member to member.\n\nThe vertebrates are just the reverse in structure. In their case\na solid internal skeleton is formed in the longitudinal axis of\nthe body, and the muscles are external to these supporting organs.\nThe articulation or metamerism itself is not visible externally in\nthe vertebrates; it is only seen in the muscular system when the\nnon-articulated skin has been removed. Then, even in the lowest\nskull-less vertebrates, the acrania, the internal skeleton of which\nconsists merely of a cylindrical, solid, and elastic axial rod\n(_chorda_), we see on each side a row of muscular plates (fifty to\neighty in the amphioxus). In this case there are not pairs of limbs,\nand it is the same with the oldest craniate animals, the cyclostoma\n(myxinoida and petromyzonta). It is only with the third class of the\nvertebrates, the true fishes (_pisces_), that two pairs of lateral\nlimbs appear--the breast-fins and belly-fins. From these, in their\nterrestrial descendants, the oldest amphibia of the Carboniferous\nPeriod, the two pairs of jointed legs--fore-legs (carpomela) and\nhind-legs (tarsomela)--are derived. These four lateral five-toed legs\nhave a very characteristic and complicated articulation, both in the\ninternal bony skeleton and the muscular system that encloses this and\nis attached to it. From the amphibia, the earliest quadrupeds, this\nlocomotive apparatus is transmitted by heredity to their descendants,\nthe three higher classes of the vertebrates, reptiles, birds, and\nmammals. As I have dealt with these important structures fully in my\n_Anthropogeny_ (chapter xxvi.), and given a number of illustrations of\nthem, I must refer the reader to that work,[8] and will only make a few\nobservations on the mammals.\n\nBoth parts of the motor apparatus, the internal bony skeleton (the\npassive supporting apparatus) and the external muscular system (the\nactive motor), exhibit a great variety of construction within the\nmammal class, in consequence of adaptation to the most different\nhabits and functions. We have only to compare the running carnivora\nand ungulata, the leaping kangaroos and jerboas, the burrowing moles\nand hyperd\u00e6i, the flying cheiroptera and bats, the fishlike swimming\nsirens and whales, and climbing lemures and apes. In all these and the\nremaining orders of the mammals the whole regular structure of the\nmotor apparatus is strikingly adapted to the habits of life which have\nbeen formed by this adaptation itself. Nevertheless, we see that the\nessential character of the inner organization which distinguishes the\nmammals as a class is not affected by this adaptation, but constantly\nmaintained by heredity. These recognized facts of comparative anatomy\nand ontogeny, and the concordant results of paleontology, prove\nconvincingly that all living and fossil mammals, from the lowest\nungulates and marsupials to the ape and man, have descended from one\ncommon stem-form, a pro-mammal, that lived in the Triassic Period;\nits earlier ancestors in the Permian Period were reptiles, and, in\nthe Carboniferous Period, amphibia. Among the characters of the\nlocomotive apparatus which are peculiar to mammals we have, on the\none hand, the structure of the vertebral column and the skull, and,\non the other hand, the formation of the muscles which are attached\nto these supporting organs. In the skull we particularly notice the\nformation of the lower jaw and the joint by which it is connected with\nthe temporal bone. This joint is temporal, and so distinguished from\nthe square joint of the other vertebrates. The latter is found in the\nmammals in the tympanic cavity of the middle-ear, between the hammer\n(the modified joint of the lower jaw, _articulare_) and the anvil (the\noriginal _quadratum_). In harmony with this remarkable modification\nof the maxillary joint, the corresponding muscles have naturally\nalso undergone a considerable transformation. A distinctive muscle\nthat is only found in the mammals and regulates their respiration is\nthe diaphragm, which completely divides the abdominal and thoracic\ncavities; the various muscles, from the blending of which it has been\nformed, still remain separate in the other vertebrates.\n\nThe many organs by means of which our human organism accomplishes its\nmanifold movements are just the same as in the apes, and the mechanism\nof their action is in no way different. The same two hundred bones,\nin the same order and composition, form our internal bony skeleton;\nthe same three hundred muscles effect our movements. The differences\nwe find in the form and size of the various muscles and bones (and\nwhich are, as is well known, also found between lower and higher\nraces of men) are due to differences in growth in consequence of\ndivergent adaptation. On the other hand, the complete agreement in the\nconstruction of the whole motor apparatus is explained by heredity from\nthe common stem-form of the apes and men. The most striking difference\nbetween the movements of the two is due to man's adaptation to the\nerect posture, while the climbing of trees is the normal habit of the\nape. However, it is unquestionable that the former is an evolution\nfrom the latter. A double parallel to this modification is seen in the\njerboa among the ungulates, and in the kangaroo among the marsupials.\nBoth these, in springing, use only the strong hinder extremities, and\nnot the weaker fore-limbs; as a result of this their posture has become\nmore or less erect. Among the birds we have an analogous case in the\npenguins (_aptenodytes_); as they no longer use their atrophied wings\nfor flight, but only in swimming, they have developed an erect posture\nwhen on land.\n\nThe human will is also not specifically different from that of the ape\nor any other mammal; and its microscopic organs, the neurona in the\nbrain and the muscular cells in the flesh, work with the same forms\nof energy, and are similarly subject to the law of substance. Hence\nit is immaterial for the moment whether one believes in the freedom\nof the will according to the antiquated creed of indeterminism, or\nwhether one holds it to be refuted scientifically by the arguments\nof modern determinists; in either case the acts of the will and\nvoluntary movements follow the same laws in man as in the ape. The high\ndevelopment of the function in civilized man, the ample differentiation\nof speech and morality, art and science--in a word, the ethical\nsignificance of the will for higher culture--is in no way discordant\nto this monistic and zoologically grounded conception. In the lower\nraces these privileges of the civilized will are only found in a slight\ndegree, and some of them are wholly wanting among the lowest races. The\ndistance between the lowest savage and the most civilized human being\nis greater, in this respect also, than that which separates the savage\nfrom the anthropoid ape. However, I refer the reader to the remarks\nI made at the close of the seventh chapter of the _Riddle_ on the\nproblem of the freedom of the will and the infinite literature relating\nthereto. The reader who desires to go further into this subject will\nfind it well treated in the works of Traugott Trunk (1902) and Paul R\u00e9e\n(1903) [also in Dr. Stout's recent little manual of psychology and Mr.\nW. H. Mallock's _Religion as a Credible Doctrine_].\n\n\n\n\nXIII\n\nSENSATION\n\n Sensation and consciousness--Unconscious and conscious\n sensation--Sensibility and irritability--Reflex sensation and\n perception of stimuli--Sensation and living force--Reaction\n to stimuli--Resolution of stimuli--External and internal\n stimuli--Conveyance of stimuli--Sensation and striving--Sensation\n and feeling--Inorganic and organic sensation--Light sensation,\n phototaxis, sight--Sensation of warmth, thermotaxis--Sensation of\n matter, chemotaxis--Taste and smell--Erotic chemicotropism--Organic\n sensations--Sensation of pressure--Geotaxis--Sensation of\n sound--Electric sensation.\n\n\nSensation is one of those general terms that have at all times been\nliable to the most varied interpretations. Like the cognate idea of\nthe \"soul,\" it is still extremely ambiguous. During the eighteenth\ncentury it was generally believed that the function of sensation was\npeculiar to animals, and was not present in plants. This opinion found\nits most important expression in the well-known principle in Linn\u00e9's\n_Systema Natur\u00e6_: \"Stones grow: plants grow and live: animals grow,\nlive, and feel.\" Albrecht Haller, who gathered up all the knowledge\nof his time relating to organic life in his _Elementa Physiologi\u00e6_\n(1766), distinguished as its two chief characters \"sensibility\" and\n\"irritability.\" The one he ascribed exclusively to the nerves, and the\nother to the muscles. This erroneous idea was subsequently refuted, and\nin our own time irritability is conceived to be a general property of\nall living matter.\n\nThe great advance made by the comparative anatomy and experimental\nphysiology of animals and plants in the first half of the nineteenth\ncentury brought to light the fact that irritability or sensibility is\na common quality of all organisms, and that it is one of the principal\ncharacteristics of vital force (_cf._ chapter ii.). The greatest merit\nin connection with its experimental study attaches to the famous\nJohannes M\u00fcller. In his classical _Manual of Human Physiology_ (1840)\nhe established his theory of the specific energy of the nerves and\ntheir dependence on the sense-organs on the one hand and the mental\nlife on the other. He devoted the fifth chapter of his book to the\nformer and the sixth to the latter, approaching particularly to\nSpinoza in his general psychological views; he treated psychology as\na part of physiology, and thus put on a sound scientific basis that\nnaturalistic conception of the place of psychology in the biological\nsystem which we now regard as the correct view. At the same time he\nproved that sensation is a function of the organism as much as movement\nor nutrition.\n\nThe view of sensation that prevailed in the second half of the\nnineteenth century was very different. On the one hand the experimental\nand comparative physiology of the sense-organs and the nervous system\nimmensely enriched our exact knowledge by the invention of ingenious\nmethods of research and the use of the great advance made by physics\nand chemistry. The famous investigations of Helmholtz and Hertwig on\nthe physics of the senses, of Matteucci and Dubois-Reymond on the\nelectricity of the muscles and nerves, and the great progress made in\nvegetal physiology by Sachs and Pfeffer, and in physiological chemistry\nby Moleschott and Bunge, enabled us to realize that even the most\nmysterious of the wonders of life depend on physical and chemical\nprocesses. By the application of the different stimuli--light, heat,\nelectricity, and chemical action--to the various sensitive or irritable\norgans under definitely controlled conditions, scientists succeeded in\nsubjecting with exactness a great part of the phenomena of stimulation\nto mathematical measurements and formul\u00e6. The science of the stimuli\nand their effects acquired a strictly physical character.\n\nOn the other hand, in most striking contradiction to the immense\nadvance of experimental physiology, we see that the general\nconception of the various vital processes, and especially of the\ninner nerve-action that converts the functions of the senses into\nmental life, is most curiously neglected. Even the fundamental idea\nof sensation, which plays the chief part in it, is disregarded more\nand more. In many of the most valuable modern manuals of physiology,\ncontaining long chapters on stimuli and stimulation, there is little or\nno mention of sensation as such. This is chiefly due to the mischievous\nand unjustifiable gulf that has once more been artificially created\nbetween physiology and psychology. As the \"exact\" physiologists\nfound the study of the inner psychic processes which take place in\nsense-action and sensation inconvenient and unprofitable, they gladly\nhanded over this difficult and obscure field to the \"psychologists\nproper\"--in other words, to the metaphysicians, who had for the\nstarting-point of their airy speculations the belief in an immortal\nsoul and divine consciousness. The psychologists readily abandoned the\ninconvenient burden of experience and _a posteriori_ knowledge, to\nwhich the modern anatomic physiology of the brain laid special claim.\n\nThe greatest and most fatal error committed by modern physiology in\nthis was the admission of the baseless dogma that all sensation must\nbe accompanied by consciousness. As most physiologists share the view\nof Dubois-Reymond, that consciousness is not a natural phenomenon,\nbut a hyperphysical problem, they leave it and this inconvenient\n\"sensation\" outside the range of their researches. This decision is,\nnaturally, very agreeable to the prevalent metaphysics; it has just as\nmuch interest in the transcendental character of sensation as in the\nliberty of the will, and thus the whole of psychology passes from the\nempirical province of natural science into the mystical province of\nmental science. For its foundation they then take the \"critical theory\nof knowledge,\" which ignores the results of the real physiological\norgans--the senses, nerves, and brain--and draws its \"superior wisdom\"\nfrom the inner mirroring of self by the introspective analysis of\npresentations and their associations. It is extraordinary that even\ndistinguished monistic physiologists suffer themselves to be taken\nin with this sort of metaphysical jugglery, and dismiss the whole of\npsychology from their province; their psychomonism readmits the soul as\na supernatural entity, and delivers it, in contrast with the \"world of\nbodies,\" from the yoke of the law of substance.\n\nImpartial reflection on our personal experience during sensation and\nconsciousness will soon convince us that these are two different\nphysiological functions, which are by no means necessarily associated;\nand the same may be said of the third principal function of the\nsoul--the will. When we learn an art--for instance, painting or\nplaying the piano--we need months of daily practice in order to become\nexpert at it. In this we experience every day hundreds of thousands\nof sensations and movements which are learned and repeated with full\nconsciousness. The longer we continue the practice and the more we\nadapt and accustom ourselves to the function, the easier and less\nconscious it becomes. And when we have practised the art for some\nyears, we paint our picture or play our piano unconsciously; we think\nno longer of all the small, subtle shades of sensation and acts of\nwill which were necessary in learning. The mere impulse of the will to\npaint the picture once more or play the piece again suffices to release\nthe whole chain of complicated movements and accompanying sensations\nwhich had originally to be learned slowly, laboriously, and with\nfull consciousness. An experienced pianist plays the most difficult\npiece--if he has learned it and repeated it thousands of times--\"half\nin a dream.\" But it needs only a slight accident, such as a mistake\nor a sudden interruption, to bring back the wandering attention to\nthe work. The piece is now played with clear consciousness. The same\nmay be said of thousands of sensations and movements which we learned\nat first consciously in childhood, and then repeat daily afterwards\nwithout noticing--such as in walking, eating, speaking, and so on.\nThese familiar facts prove of themselves that consciousness is a\ncomplicated function of the brain, by no means necessarily connected\nwith sensation or will. To bind up the ideas of consciousness and\nsensation inseparably is the more absurd, as the mechanism or the real\nnature of consciousness seems very obscure to us, while the idea of it\nis perfectly clear: we know that we know, feel, and will.\n\nThe word \"irritability\" is generally taken by modern physiology to mean\nthat the living matter has the property of reacting on stimuli--that\nis to say, of responding by changes in itself to changes in its\nenvironment. The stimulus, or action of a foreign energy, must,\nhowever, be felt by the plasm before the corresponding stimulated\nmovement (in the form of various manifestations of energy) will be\nproduced. Hence the question whether this sensation is (in certain\ncases) associated with consciousness or (generally) remains unconscious\nis of a subordinate interest. The plant that is caused to open its\nfloral calyx by the stimulus of light acts just as unconsciously in\nthis as the coral that spreads out its crown of tentacles under the\nsame influence; and when the sensitive carnivorous plant (_dion\u00e6a_ or\n_drosera_) closes its leaves in order to catch and destroy the insect\nsitting on them, it acts in the same way as the sensitive actinia or\ncoral when it draws in its crown of tentacles for the same object--in\nboth cases without consciousness! We call these unconscious movements\n\"reflex actions.\" I have dealt somewhat fully with these reflex\nmovements in the seventh chapter of the _Riddle_, and must refer the\nreader thereto. This elementary psychic function always depends on\na conjunction of sensation and movement (in the widest sense). The\nmovement that the stimulus provokes is always preceded by a sensation\nof the influence exerted.\n\nModern physiology makes desperate efforts to avoid the use of the\nword \"sensation\" and substitute for it \"perception of stimulus.\" The\nchief blame for this misleading expression is due to the arbitrary\nand unjustified separation of psychology from physiology. The latter\nis supposed to occupy itself with the material phenomena and physical\nchanges, leaving to psychology the privilege of dealing with the\nhigher mental phenomena and metaphysical problems. As we reject this\ndistinction altogether on monistic principles, we cannot consent\nto separate sensation from the perception of stimuli--whether this\nsensation be accompanied with consciousness or not. Moreover, modern\nphysiology, in spite of its desire to keep clear of psychology, sees\nitself compelled in a thousand ways to use the words \"sensation\" and\n\"sensitive,\" especially in the science of the organs of sense.\n\nWhat we call sensation or perception of stimuli may be regarded\nas a special form of the living force or actual energy (Ostwald).\nSensitiveness or irritability, on the other hand, is a form of virtual\nor potential energy. The living substance at rest, which is sensitive\nor irritable, is in a state of equilibrium and indifference to its\nenvironment. But the active plasm, that receives and feels a stimulus,\nhas its equilibrium disturbed, and corresponds to the change in its\nenvironment and its internal condition. This response of the organism\nto a stimulus is called \"reaction\"--a term that is also used (in\nthe same sense) in chemistry to express the interaction of bodies\non each other. At each stimulation the virtual energy of the plasm\n(sensitiveness) is converted into living or kinetic force (sensation).\nThe share of the stimulus in this conversion is described as a\n\"release\" of energy.\n\nThe term \"reaction\" stands in general for the change which any body\nexperiences from the action of another body. Thus, for instance, to\ntake the simplest case, the interaction of two substances in chemistry\nis called a reaction. In chemical analysis the word is used in a\nnarrower sense to denote that action of one body on another which\nserves to reveal its nature. Even here we must assume that the two\nbodies feel their different characters; otherwise they could not act\non each other. Hence every chemist speaks of a more or less \"sensitive\nreaction.\" But this process is not different in principle from the\nreaction of the living organism to outer stimuli, whatever be their\nchemical or physical nature. And there is no more essential difference\nin psychological reaction, which is always bound up with corresponding\nchanges in the psychoplasm, and so with a chemical conversion of\nenergy. In this case, however, the process of reaction is much more\ncomplicated, and we can distinguish several parts or phases of it:\n1, the outer excitation; 2, the reaction of the sense-organ; 3, the\nconducting of the modified impression to the central organ; 4, the\ninternal sensation of the conducted impression; and, 5, consciousness\nof the impression.\n\nThe important idea of a release of energy--the term we give to the\neffect of the stimulus--is also used in physics. If we put a piece of\nburning wood in a barrel of powder, the flame causes an explosion. In\nthe case of dynamite a simple mechanical shock is enough to produce\nthe most enormous expenditure of force in the explosive matter. When\nwe discharge a bow the slight pressure of the finger on the tense\ncord suffices to send out the arrow or bolt on its deadly mission. So\nalso a sound or a ray of light that strikes the ear or eye suffices\nto bring about a number of complex effects by means of the nervous\nsystem. In the fertilization of the ovum by the male sperm the chemical\nconjunction of the two formative principles is sufficient to cause the\ngrowth of a new human being out of the microscopic plasma-globule, the\nstem-cell (_cytula_). In these and thousands of other reactions a very\nslight shock suffices to provoke the largest effects in the stimulated\nsubstance. This shock, which we call a release of energy, is not the\ndirect cause of the considerable result, but merely the occasion for\nbringing it about. In these cases we have always a vast accumulation\nof virtual energy converted into living force or work. The magnitude\nof the two forces has no relation at all to the smallness of the shock\nwhich led to the conversion. In this we have the difference between\nstimulated action and the simple mechanical action of two bodies on\neach other, in which the quantity of the energy expended is equal on\nboth sides, and there is no stimulus.\n\nThe immediate effect of a stimulus on living matter can best be\nfollowed in external physical or chemical stimuli, such as light,\nheat, pressure, sound, electricity, and chemical action. In these\ncases physical science is often able to reduce the life-process to the\nlaws of inorganic nature. This is more difficult with the internal\nstimuli within the organism itself, which are only partly exposed\nto physiological investigation. It is true that here also the task\nof science is to reduce all the biological phenomena to physical and\nchemical laws. But it can only discharge a part of this difficult task,\nas the phenomena are too complicated, and their conditions too little\nknown in detail, to say nothing of the crudeness and imperfectness of\nour methods of research. Yet, in spite of all this, comparative and\nphylogenetic physiology convinces us that even the most complicated\nof our internal excitations, and particularly the mental activity of\nthe brain, depend just as much as the outer stimulations on physical\nprocesses, and are equally subject to the law of substance. This is, in\nfact, true of reason and consciousness.\n\nIn man and all the higher animals the stimuli are received by the\norgans of sense and conducted by their nerves to the central organ. In\nthe brain they are either converted into specific sensations in the\nsense-centres, or conveyed to the motor region, where they provoke\nmovements. The conduction of stimuli is simpler in the lower animals\nand the plants; the tissue-cells either directly affect each other or\nare connected by fine threads of plasm. In the unicellular protists\nthe stimulus which strikes one particular spot of the surface may be\nimmediately communicated to the other parts of the unified plasmic body.\n\nWe shall see in the course of our inquiry that the simplest form of\nsensation (in the widest sense) is common to inorganic and organic\nbodies, and thus that sensitiveness is really a fundamental property\nof all matter, or, more correctly, all substance. We may, therefore,\nascribe sensation to the constituent atoms of matter. This fundamental\nthought of hylozoism, expressed long ago by Empedocles, has lately\nbeen very definitely urged, especially by Fechner. However, the able\nfounder of psychophysics (_cf._ the _Riddle_, p. 35) assumes that\nconsciousness (or thought, in the Spinozistic sense) always accompanies\nthis universal property of sensation. In my opinion, consciousness is a\nsecondary psychic function, only found in man and the higher animals,\nand bound up with the centralization of the nervous system. Hence it is\nbetter to speak of the unconscious sensation of the atoms as _feeling_\n(_\u00e6sthesis_), and their unconscious will as _inclination_ (_tropesis_).\nIt finds expression in the one-sided action of a stimulus as a\n\"directed movement\" or \"stimulated movement\" (_tropismus_ or _taxis_).\n\nThe familiar ideas of sensation and feeling are often confused, and\nemployed in very different ways in both physiology and psychology. The\nmetaphysical tendency which so completely separates the two sciences,\nand the physiological tendency which agrees with it, regard feeling\nas a purely psychic or spiritual function, whereas in the case of\nsensation they have to admit the connection with bodily functions,\nespecially sense-action. In my opinion, the two ideas are purely\nphysiological and cannot be sharply separated, or only in the sense\nthat sensation relates more to the external (objective) part of the\nsensory nerve-process, and feeling to the internal (subjective) part.\nHence we may define the difference in a general way by saying that\nsensation perceives the different qualities of the stimuli, and feeling\nonly the quantity, the positive or negative action of the stimulus\n(pleasure or pain). In this last and widest sense we may ascribe\nthe feeling of pleasure and pain (in the contact with qualitatively\ndiffering atoms) to all atoms, and so explain the elective affinity in\nchemistry (synthesis of loving atoms, inclination; analysis of hating\natoms, disinclination).\n\nOur monistic system (whether it be taken as energism or materialism,\nor more correctly as hylozoism) regards all substance as having\n\"soul\"--that is to say, endowed with energy. In the chemical analysis\nof organisms we do not find any elements that are not found in\ninorganic nature; we find that the movements in organisms obey the\nsame laws of mechanics as the latter; we believe that the conversion\nof energy in the living matter occurs in the same way, and is provoked\nby the same stimuli, as in inorganic matter. We are forced to conclude\nfrom. these experiences that the perception of stimuli--sensation in\nthe objective and feeling in the subjective sense--is also generally\npresent in the two. All bodies are in a certain sense \"sensitive.\" It\nis just in this dynamic conception of substance that monism differs\nessentially from the materialistic system, which regards one part of\nmatter as \"dead\" and insensitive. In this we have the best means of\njoining consistent materialism or realism with consistent spiritualism\nor idealism. But, as a first condition of such a union, we must demand\na recognition that organic life is subject to the same general laws\nas inorganic nature. In both cases the outer world acts alike as\na stimulus on the inner world of the body. We can easily see this\nif we glance at the various kinds of sensation which correspond to\nthe various kinds of stimuli. Light and heat, external and internal\nchemical stimuli, pressure and electricity, cause analogous sensations\nand modifications in their effect on organic and inorganic bodies.\n\nThe effect which the light-stimulus has on living matter, the sensation\nof light that results, and the chemical changes of energy that follow,\nare of great physiological importance in all organisms. We might even\nsay that sunlight is the first, oldest, and chief source of organic\nlife; all other exertions of force depend in the long run on the\nradiant energy of sunlight. The oldest and most important function\nof plasm--one which is at the same time a cause of its formation--is\ncarbon-assimilation; and this plasmodomism is directly dependent on\nsunlight. If it acts in a one-sided way, it causes the particular form\nof stimulation which we call phototaxis or heliotropism. This is of a\npositive character--that is to say, they turn towards the source of the\nlight--in the great majority of organisms, both protists and histona.\nEverybody knows that flowers that are growing in the window of a room\nturn to the light. However, many organisms which have grown accustomed\nto living in the dark are heliotropically negative; they shun the light\nand seek darkness, such as the fungi, many lucifugous mosses and ferns,\nand many deep-sea animals.\n\nThe principal organs of light-sensation in the higher animals are the\neyes; they are wanting in many of the lower animals as well as the\nplants. The essential difference between the real eye and a part of\nthe skin that is merely sensitive to light is that the eye can form a\npicture of objects in the outer world. This faculty of vision begins\nwith the formation of a small convergent lens, a biconvex refracting\nbody at a certain spot on the surface. Dark pigment-cells which\nsurround it absorb the light-rays. From this first phylogenetic form of\nthe organ of vision up to the elaborate human eye there is a long scale\nof evolutionary stages--not less extensive and remarkable than the\nhistorical succession of artificial optical instruments from the simple\nlens to the complicated modern telescope or microscope. This great\n\"wonder of life\"--the long scale of the evolution of the eye--has an\ninteresting tearing on many important questions of general physiology\nand phylogeny. We can, in this case, see clearly how a very complicated\nand purposive apparatus can arise in a purely mechanical way, without\nany preconceived design or plan. In other words, we can see how an\nentirely new function--and one of its principal functions, vision--has\narisen in the organism by mechanical means.\n\nThe advanced vision of the higher animals is made up of a great number\nof different functions, with a corresponding complexity of detail in\nthe anatomic structure of the eye. No other organ, after the brain,\nis so necessary as the eye for the multifarious vital activities of\nthe higher animals, and especially for the mental life of civilized\nman and the progress of art and science. What would the human mind be\nif we could not read, write, and draw, and have a direct knowledge\nthrough the eye of the forms and colors of the outer world? Yet this\ninvaluable structure is only the highest and most perfect stage in\nthe long chain of evolutionary processes which has its starting-point\nin the general sensitiveness to light, or the photic irritability of\nplasm. However, we find a number of varieties and grades of this even\namong the unicellular protists, and, indeed, the very lowest and oldest\nof the protists, the monera. Various species of both the chromacea and\nthe bacteria are heliotropic to different degrees, and have a fine\nsensitiveness to the strength of the light stimulus.\n\nThe stimulating effect which light has on the homogeneous plasm of the\nmonera is also found in a number of inorganic bodies. In these cases\nthe photic stimulus produces partly chemical and partly mechanical\nchanges. Every chemist speaks of substances that are more or less\n\"sensitive\" to light; the photographer speaks of his \"sensitive\nplates,\" the painter of his \"sensitive colors.\" Many chemical compounds\nare so sensitive to light that they are destroyed at once in sunlight,\nand so have to be kept in the dark. There is no other word but\n\"sensation\" to express the attitude of the atoms towards each other\nwhich becomes so conspicuous in these cases under the influence of\nsunlight. It seems to me that this phenomenon is a clear justification\nof our hylozoic monism when it affirms that all matter is psychic. In\nmetaphysics sensation is held to be an essential property of the soul.\n\nIn the same general way as light the heat-stimulus acts on organisms,\nand causes the sensations, sometimes pleasant and sometimes unpleasant,\nwhich we call the subjective feeling of heat, warmth, coolness, or\ncold. The sense-organ that receives these impressions of temperature is\nthe surface of the unicellular plasmic body in the protists, and the\nskin (epidermis) that protects the surface from the outer world in the\nhistona. In all living things the temperature of the surrounding medium\n(water or air) has a great influence in regulating the life-processes;\nin the stationary animals and plants it is the temperature of the\nground to which they are attached. This temperature must always be\nbetween the freezing-point and boiling-point of water, as fluid water\nis indispensable for the imbibition of the living matter and the\nmolecular movements within the plasm. At the same time, some of the\nlower protists (chromacea, bacteria) can endure very high and very\nlow temperatures, but only for a short time. Some protists (monera\nand diatomes) can stand a temperature of 200\u00b0 C. for several days,\nand others can be heated above boiling-point without being killed.\nArctic and High-Alpine plants and animals may be in a frozen condition\nfor several months, yet live again when they are thawed. However, the\nresistance to these extremes of cold lasts for only a limited time, and\nin the frozen state all vital functions are at a standstill.\n\nIn the great majority of living things the vital activity is confined\nwithin narrow limits of temperature. Many plants and animals in the\ntropics which have been accustomed for thousands of years to the\nconstancy of the hot equatorial climate can endure only very restricted\nvariations of temperature. On the other hand, many of the inhabitants\nof Central Siberia, where the climate is very hot in the short summer\nand very cold in the long winter, can stand great variations. Thus\nthe living plasm has experienced considerable changes in its sense\nof warmth through adaptation to different environments; not only the\nmaximum and the minimum, but the optimum (most agreeable point),\nis subject to very great variations. This can easily be observed\nand followed experimentally in the phenomena of thermotaxis or\nthermotropism--that is to say, the effect that follows from a one-sided\naction of the heat-stimulus. The organism that falls below the minimum\nof temperature is said to be stiff with cold, while the organism that\nrises above the maximum is stiff with heat.\n\nThe heat-stimulus acts on inorganic as well as organic bodies, like\nthe light-stimulus. The law holds good in both cases that higher\ntemperatures increase sensation, while lower ones paralyze it. There is\na minimum, an optimum, and a maximum, for many chemical and physical\nprocesses in the inorganic world. As far as the melting effect of water\nis concerned, freezing is the minimum of the heat stimulus and boiling\nthe maximum. As the various chemical compounds meet in water at very\ndifferent temperatures, we have an optimum for many substances--that is\nto say, a degree of warmth which is most favorable to the solution of\na given quantity of a solid body in water. On the whole, the law holds\nfor chemical processes that they are accelerated by high temperatures\nand retarded by low ones (like the human passions!); the former have\na stimulating and the latter a benumbing effect. As the action of the\nvarious chemical compounds on each other is determined by the nature\nof the elements and their affinities, we must trace the variations in\ntheir conduct towards thermic stimuli to a sensation of temperature in\nthe constituent atoms; increase of temperature stimulates it, while\ndecrease lessens or paralyzes it. Here, again, the simple inorganic\nprocesses have a general resemblance to the complicated vital phenomena\nin the organic body.\n\nSince we regard the whole of organic life as, in the ultimate analysis,\nmerely a very elaborate chemical process, we shall quite expect that\nchemical stimuli are the most important factors in sensation. And this\nis so in point of fact; from the simplest moneron up to the most highly\ndifferentiated cell and on to the flower in the plant and the mental\nlife of man, the vital processes are dominated by chemical forces and\nconversions of energy, which are set in play by external or internal\nchemical stimuli. The excitation which they produce is called, in a\ngeneral way, \"sensation of matter\" or chem\u00e6sthesis; the basis of it\nis the mutual relation of the chemical elements which we describe as\nchemical affinity. In this affinity we have the play of attractive\nforces which lie in the nature of the elements themselves, especially\nin the peculiar properties of their constituent atoms; and this cannot\nbe explained unless we ascribe unconscious sensation (in the widest\nsense) to the atoms, an inherent feeling of pleasure and the reverse,\nwhich they experience in the contact of other atoms (the \"loves and\nhatreds of the elements\" of Empedocles).\n\nThe numbers of different stimuli that act chemically on the plasm\nand excite its \"sensation of matter\" may be divided into two\ngroups--external and internal stimuli. The latter lie within the\norganism itself, and cause the internal \"organic sensations\";\nthe former are in the outer world, and are felt as taste, smell,\nsex-impulse, etc. In the higher animals special chemical sense-organs\nhave been developed for these chemical stimuli. As these are well known\nto us from our own human experience, and comparative physiology shows\nus the same structures in the higher animals, we will deal first with\nthem. In general the same law holds for these external chemical stimuli\nas for optical and thermic stimuli; we can recognize a maximum limit\nof their action, a minimum below which they fail to stimulate, and an\noptimum or stage in which their influence is strongest.\n\nThe important part played in human life by taste and the pleasure\nassociated with it is well known. The careful choice and preparation\nof savory food--which has become an art in gastronomy and a branch\nof practical philosophy in gastrosophy--was just as important two\nthousand years ago with the Greeks and Romans as it is to-day in royal\nbanquets or the Lucullic dinners of millionaires. The excitement that\nwe see associated with this refined combination of rich foods and\ndrinks, and that finds expression in so many speeches and toasts, has\nits philosophic root in the harmony of gustatory sensations and the\nvarying play of stimuli that the delicate dishes and wines exercise\non the organs of taste, the tongue and palate. The microscopic organs\nof these parts of the mouth are the gustatory papill\u00e6--cup-shaped\nstructures, covered with spindle-shaped \"taste-cells,\" and having a\nnarrow opening into the cavity of the mouth. When sapid matters, drinks\nand fluid or loose particles of food, touch the taste-cells, they\nexcite the fine terminal branchlets of the gustatory nerve which enters\nthe cells. As we find that there are similar structures in most of the\nhigher animals, and that they also choose their food with some care,\nwe may confidently assume that they have sensations of taste like man.\nHowever, no trace of this is found in many of the lower animals; in\nthese cases it is impossible to lay down a line of demarcation between\ntaste and smell.\n\nIn man and the higher air-breathing vertebrates the seat of the sense\nof smell is in the nostrils; in man it is especially that part of the\nmucous lining of the nasal cavity which we call the \"olfactory region\"\n(the uppermost part of the nasal dividing wall, the superior and middle\nmeatus). It is necessary for a sensation of smell that the odorous\nmatter, or olfactory stimuli, be brought in a finely divided condition\nover the moist olfactory membranes. When they touch the olfactory\ncells--slender, rod-shaped cells with very fine hairs at the free\nend--they excite the ends of the olfactory nerve which are connected\nwith the cells.\n\nIn many animals, especially mammals, the sense of smell has a much more\nimportant part in life than it has in man, in whom it is relatively\nfeeble. It is well known that dogs and other carnivora, and even\nungulates, have a much keener smell. In these cases the nasal cavity,\nwhich is the seat of the sense, is much larger, and the muscles in it\nare much stronger. The nostrils of the air-breathing vertebrates have\nbeen developed from a pair of open nasal depressions in the skin of\nthe fish's head. But in these aquatic vertebrates the chemical action\nof the olfactory stimuli must be of a different character, like the\nsensation of taste. The odorous matter is, in these cases, brought\ninto contact with the olfactory membrane in a liquid form (in which\ncondition it is not perceptible to man). In fact, the division between\nthe senses of smell and taste disappears altogether in the lower\nanimals. These two \"chemical senses\" are closely related, and have a\ncommon feature in the direct chemical action of the stimulus on the\nsensitive part of the skin.\n\nA chemical sensation of matter that corresponds completely to the real\ntaste-sensation in the higher animals is found in some of the higher\ncarnivorous plants. The leaves of the sun-dew (_drosera rotundifolia_)\nare very sensitive insect-traps, and are armed at the edge with\nknob-like tentacles, sticky hairs that secrete an acid, flesh-digesting\njuice. When a solid body (but not a raindrop) touches the surface of\nthe leaf the stimulus acts in such a way on the tentacle heads as to\ncontract the leaf. But the acid fluid which serves for digestion,\nand corresponds to the gastric juice in the animal, is only secreted\nby the corpuscles if the solid foreign body is nitrogenous (flesh or\ncheese). Hence the leaves of these insectivorous plants taste their\nmeat diet, and distinguish it from other solids, to which they are\nindifferent. In the broader sense, in fact, we may describe the points\nof the roots of plants as organs of taste; they plunge into the richer\nparts of the earth which yield more nourishment, and avoid the poor\nparts. In unicellular plants and animals the action of chemical stimuli\nis especially conspicuous when it is one-sided, and provokes definite\nmovements in one particular direction (_chemotaxis_).\n\nThe movements of unicellular organisms that are provoked by chemical\nstimuli and are known as chemotropism (more recently as chemotaxis) are\nparticularly interesting because they show the existence of a chemical\nsensitiveness, somewhat resembling taste or smell, in the lowest\norganisms, and even in the homogeneous plasm of the monera. Repeated\nexperiments of Wilhelm Engelmann, Max Verworn, and others, have shown\nthat many bacteria, diatomes, infusoria, rhizopods, and other protists,\nhave a similar sense of taste; they move towards certain acids (for\ninstance, a drop of malic acid) or a bubble of oxygen that lies on\none side of the drop of water in which the protists are under the\nmicroscope. Many pathogenetic bacteria secrete poisonous substances\nwhich are very injurious to the human frame. The active white\nblood-cells, leucocytes, in the human blood have a special \"taste\" for\nthese bacteria-poisons, and concentrate in large quantities, by means\nof their am\u0153boid movements, at those parts of the body where they\nare secreted. If the leucocytes prove the stronger in their struggle\nwith the bacteria, they destroy them, and in this way they act as\nsanitary officers in keeping poisonous infection out of our organism.\nBut if the bacteria win the battle, they are transported into other\nparts of the body by the leucocytes; they distinguish their plasm by\ntaste, and may cause a deadly infection.\n\nWe have a particularly interesting and important species of chemical\nirritation in the mutual attraction of the two sex-cells, to which\nI gave the name of chemotropism thirty years ago, and which I\ndescribed as the earliest phylogenetic source of sexual love (see the\n_Anthropogeny_, chapters vii. and xxix.). The remarkable phenomena\nof impregnation, the most important of all the processes of sexual\ngeneration, consist in the coalescence of the female ovum and the\nmale sperm-cell. This could not take place if the two cells had not a\nsensation of their respective chemical constitution and disposition\nfor union; they come together under this impulse. This sexual affinity\nis found at the lowest stages of plant life, in the protophyta and\nalg\u00e6. With these both cells--the smaller male microgameta and the\nlarger female macrogameta--are often mobile, and swim about in order\nto effect a union. In the higher plants and animals only the small\nmale cell is mobile as a rule, and swims towards the large immobile\novum in order to blend with it. The sensation that impels it is of a\nchemical nature, allied to taste and smell. This has been proved by\nthe splendid experiments of Pfeffer, who showed that the male ciliated\ncells of ferns are attracted by malic acid, and those of the mosses by\ncane-sugar, just in the same way as by the exhalation from the female\novum. Conception depends on exactly the same erotic chemotropism in the\nfertilization of all the higher organisms.\n\nErotic chemotropism must be regarded as a general sense-function of the\nsexual cells in all amphigonous organisms, but in the higher organisms\nspecial forms of the sex-sense, connected with specific organs, are\ndeveloped; as the source of sexual love they play a most important\npart in the life of many of the histona. In man and most of the higher\nanimals these feelings of love are associated with the highest features\nof psychic life, and have led to the formation of some most remarkable\ncustoms, instincts, and passions. Wilhelm B\u00f6lsche has given us an\nadmirable selection from this infinitely rich and attractive realm\nin his famous _Life of Love in Nature_ (1903). It is well known that\nthis sexual sense as we have it in man has been developed from the\nnearest related mammals, the apes. But while it offers a shameless and\nrepulsive spectacle in many of the apes, it has been greatly ennobled\nand refined in man in the development of civilization. However, the\nsexual sense-organs and their specific energy have remained the same.\nIn the vertebrates and the articulates and many other metazoa the\ncopulative organs are equipped with special cell-forms (voluptuous\nparticles), which are the seat of intensely pleasurable feelings (see\nthe _Anthropogeny_, chapter xxix., plate 30). The pubic hairs which\nclothe the _mons Veneris_ are also delicate organs of the sex-sense,\nand so are the tactile hairs about the mouth. In these cases the\ncorrelation between the sensitive forms of energy in the copulative\norgans and the psychic functions of the central nervous system has\nbeen remarkably developed. Moreover, a large part of the rest of the\nskin may co-operate as a secondary organ of the sex-sense, as is seen\nin the effect of caressing, stroking, embracing, kissing, etc. Goethe,\nat once the greatest lyric poet and the subtlest and profoundest\nmonistic philosopher of Germany, has given unrivalled expression to\nthis sensual, yet supersensual, basis of sexual love. Ontogeny teaches\nunmistakably that its elementary organs, the epidermic cells, develop\nentirely from the ectoderm.\n\nBy \"organic sensations\" modern physiology understands the perception\nof certain internal bodily states, which are mostly brought about by\nchemical stimuli (to a small extent by mechanical and other irritation)\nin the organs themselves. As subjective feelings of the organism itself\nthese states are most aptly called \"feelings\"--the positive states,\npleasure, comfort, delight; the negative, discomfort, pain, etc.\nThese organic sensations (also called common sensations or feelings)\nare of great importance for the self-regulation of the complicated\norganism. To the positive organic sensations belong not only the bodily\nfeeling of satiety, repose, or comfort, but also the psychic feelings\nof joy, good humor, mental rest, etc. Among negative common feelings\nwe have not only hunger and thirst, bodily fatigue, bodily pain,\nsea-sickness, etc., but also mental strain, vertigo, bad humor, and\nso on. Between the two groups we have the third category of neutral\norganic sensations, which involve neither pleasure nor pain, but merely\nthe perception of certain internal conditions, such as muscular strain\n(in lifting heavy objects), the disposal of the limbs (in crossing the\nlegs), and so on.\n\nChemical sensation is just as general and important in organic nature\nas in the life of organisms. In this case it is nothing less than the\nbasis of chemical affinity. No chemical process can be thoroughly\nunderstood unless we attribute a mutual sensation to the atoms,\nand explain their combination as due to a feeling of pleasure and\ntheir separation to a feeling of displeasure. The great Empedocles\n(fifth century B.C.) explained the origin of all things long ago by\nthe various combination of pure elements, the interaction of love\n(attraction) and hate (repulsion). This attraction or repulsion is, of\ncourse, unconscious, just as in the instincts of plants and animals. If\none prefers to avoid the term \"sensation,\" it may be called \"feeling\"\n(_\u00e6sthesis_), while the (involuntary) movement it provokes may be\ncalled \"inclination\" (_tropesis_), and the capacity for the latter\n\"tropism\" (more recently _taxis_, _cf._ chapter xii. of the _Riddle_).\nWe may illustrate it from the simplest case of chemical combination.\nWhen we rub together sulphur and mercury, two totally different\nelements, the atoms of the finely divided matter combine and form a\nthird and different chemical body, cinnabar. How would this simple\nsynthesis be possible unless the two elements _feel_ each other, move\ntowards each other, and _then_ unite?\n\nWe find universally distributed in nature the sensation of the\nmechanical stimulus of gravitation, the most comprehensive statement\nof which is given in Newton's law of gravity. According to this\nfundamental and all-ruling law, any two particles of matter are\nattracted in direct proportion to their mass and inverse proportion to\nthe square of their distance. This form of attraction, also, can be\ntraced to a \"sensation of matter\" in the mutually attracting atoms.\nThe local sensation that any body provokes by contact with the surface\nof an organism is felt as pressure (_baros_). A stimulus that causes\nthis pressure alone brings about a counter-pressure as a reaction,\nand an effort to neutralize it, the pressure-movement (_barotaxis_\nor _barotropism_). Sensitiveness to pressure or the contact of solid\nbodies is found throughout the organic world; it can be proved\nexperimentally among the protists as well as the histona. Special\nsense-organs have been developed in the skin of the higher animals as\nthe instruments of this pressure-sense (bar\u00e6sthesis) in the form of\ntactile corpuscles; they are most numerous at the finger-tips and other\nparticularly sensitive parts. In many of the higher animals there is\na fine sense of touch in the feelers or tentacles, or (in the higher\narticulates) in the horns or antenn\u00e6. Moreover, these tactile and\nprehensile organs are also very widely found among the higher plants,\nespecially the climbing plants (vines, bryony, etc.). Their slender\ncreepers, which roll out spirally, have a very delicate feeling\nfor the nature of the supports which they embrace; they distinguish\nbetween smooth and rough, thick and thin supports, and prefer the\nlatter. Many of the higher plants, which are particularly sensitive to\npressure, have, to an extent, special organs of touch (tentacles), and\nreveal this by the movements of their leaves (the sensitive plants,\n_mimosa_, _dion\u00e6a_, _oxalis_). But even among the unicellular protists\nwe find that the contact of solid bodies has an irritating effect, the\nperception of which provokes corresponding movements (_thigmotaxis_ or\n_thigmotropismus_). A peculiar form of pressure-sensation is produced\nin many organisms by the flow of liquids; in the mycetozoa, for\ninstance, it provokes counter-movements (_rheotaxis_, _rheotropismus_),\nas Ernst Strahl showed by his experiments on _\u00e6thelium septicum_.\n\nWe have an interesting analogy to the thigmotaxis of the viscous living\nplasm in the elasticity of solid inorganic bodies, such as an elastic\nsteel-rod. In virtue of its springy nature, the elastic rod reacts\non the pressure of force that has bent it, and endeavors to regain\nits former position. The spiral spring sets the works of the clock in\nmotion in virtue of its elasticity.\n\nA very important part is played in botany by the action of gravitation\non the growth of plants. The attraction towards the centre of the earth\ncauses the positively geotropic roots to grow vertically into the\nearth, while the negatively geotropic stalk pushes out in the opposite\ndirection. This applies also to a number of stationary animals which\nare attached to the ground by roots, such as polyps, corals, bryozoa,\netc. And even the locomotion of free animals, the disposition of\ntheir bodies to the ground, the position and posture of their limbs,\netc., is determined partly by the feeling of gravitation, and partly\nby adaptation to certain functions which resist this, as in running,\nswimming, and so on. All these geotropic sensations belong to the\nsame group of barotactile phenomena, as the fall of a stone or any\nother effect of gravitation that depends on an inorganic feeling of\nattraction.\n\nAs a result of these adaptations, we find a distinct sense of space\ndeveloped in the higher, free-moving animals. The feeling of the three\ndimensions of space becomes an important means of orientation, and in\nthe vertebrates, from the fishes up to man, the three spiral canals\nin the inner ear are developed as special organs of this. These three\nsemicircular canals, which lie vertically to each other in the three\ndimensions of space, are the organs of the sensation that guides the\nmovements of the head, and, in relation to this, for the normal posture\nof the body and the feeling of equilibrium. If the three spiral canals\nare destroyed, the equilibrium is lost; the body totters and falls.\nHence, these organs are not of an acoustic, but a static or geotactic\ncharacter; and the same may be said of the so-called \"auditory\nvesicles\" of many of the lower animals--round vesicles which contain\na liquid and a solid body, the otolith. When this body changes its\nposition with the change of posture of the whole frame, it presses on\nthe fine auditory hairs, or delicate terminations of the auscultory\nnerve, which enters the vesicle. In fact, the sense of equilibrium is\noften combined with the sense of hearing.\n\nThe perception of noises and tones, which we call hearing, is\nrestricted to a section of the higher, free-moving animals; if, that is\nto say, the above-mentioned \"auditory vesicles\" in the lower animals\ndo not have acoustic as well as static sensations. The specific\nsensation of hearing is due to vibration of the medium in which the\nanimal lives (air or water), or to vibrations of solid bodies (such as\ntuning-forks) which are brought into touch with them. If the vibrations\nare irregular, they are felt as \"noises\"; if regular, they are heard\nas \"tones\" or notes; when a number of tones together (fundamental\nand over-tones) excite a complex sensation, we have \"timbre.\" The\nvibrations of the sounding body are borne to the auditory cells, which\nrepresent the terminal extensions of the auscultory nerve. The specific\nsensation of hearing can, therefore, be traced originally to the sense\nof pressure, from which it has been evolved. As the organ of hearing\nis, like the eye, one of the principal instruments of the higher mental\nlife, and as the refined musical hearing of civilized man is often\ntaken to be a metaphysical power of the soul, it is important to note\nthat here again the starting-point was purely physical--that is to say,\nit can be traced to the sense of pressure of matter, or gravitation.\n\nThe great importance of electricity as an agency in nature, both\norganic and inorganic, has only lately been fully appreciated. Electric\nchanges are connected with many (if not, as is now supposed, with\nall) chemical and optical processes. Man himself and most of the\nhigher animals have no electric organs (apart from the eye), and no\nsense-organs that experience a specific electric sensation. It is\nprobably otherwise with many of the lower animals, especially those\nthat develop free electricity, such as the electric fishes. The larv\u00e6\nof frogs and embryos of fishes, if put in a vessel of water through\nwhich a galvanic current is sent, place themselves when it is closed\nwith their longitudinal axis in the direction of the current, with\nthe head directed to the anode and the tail to the cathode (Hermann).\nAgain, the luminous sea-animals which cause the beautiful phenomenon\nof the illumination of the sea, and the glow-worms and other luminous\norganisms, have probably an unconscious feeling of the flow of electric\nenergy associated with these phenomena. Many plants show a direct\nreaction to electric stimuli; when, for instance, we send a constant\ngalvanic current for some time through the points of their roots (very\nsensitive organs, compared by Darwin to the brain of the animal), they\nbend towards the cathode.\n\nMany of the protists are very sensitive to electric currents, as Max\nVerworn especially proved by a series of beautiful experiments. Most\nof the ciliated infusoria and many of the rhizopods (_am\u0153ba_) are\ncathodically sensitive or negatively galvanotactic. When we send a\nconstant electric current through a drop of water in which thousands of\n_param\u0153cium_ are moving about, all the infusoria swim at once, with\nthe anterior pole of the body foremost, towards the cathode or negative\npole; they accumulate about it in great crowds. If the direction of the\ncurrent is now changed, the whole swarm at once make in the opposite\ndirection for the new cathode. Most of the flagellate infusoria do just\nthe reverse; they are anodically sensitive or positively galvanotactic.\nIn a drop of water, in which swarms of _polytoma_ are moving about,\nall the cells swim at once towards the anode or positive pole, when an\nelectric current is sent through. The opposite galvanotropic behavior\nof these two groups of infusoria in a drop of water, in which they\nare mixed together, is very interesting; as soon as a constant stream\nenters it, the ciliata fly to the cathode and the flagellata to the\nanode. When the current is reversed the two swarms rush at each other\nlike hostile armies, cross in the middle of the drop, and gather at the\nopposite poles. These and other phenomena of galvanic sensation show\nclearly that the living plasm is subject to the same physical laws as\nthe water that is decomposed into hydrogen and oxygen by an electric\ncurrent. Both elements _feel_ the opposite electricities.\n\n\nSCALE OF SENSATION AND IRRITABILITY\n\n 1st Stage: SENSATION OF ATOMS. Affinity of the elements in every\n chemical combination.\n\n 2d Stage: SENSATION OF MOLECULES (groups of atoms): in the attraction\n and repulsion of molecules (positive and negative electricity, etc.).\n\n 3d Stage: SENSATION OF PLASTIDULES (micella, biogens, or\n plasma-molecules): in the simplest vital process of the monera\n (chromacea and bacteria).\n\n 4th Stage: SENSATION OF CELLS: irritability of the unicellular\n protists (protophyta and protozoa): erotic chemotropism connected\n with the nucleus and trophic with the cell-body.\n\n 5th Stage: SENSATION OF C\u0152NOBIA (volvox, magosph\u00e6ra). With the\n formation of cell-communities we have association of sensations\n (individual feeling on the part of the social cells together with\n common feeling on the part of the community).\n\n 6th Stage: SENSATION OF THE LOWER PLANTS. In the metaphyta or\n tissue-plants all the cells are still equally sensitive at the lower\n stages: there are no special sense-organs.\n\n 7th Stage: SENSATION OF THE HIGHER PLANTS. In the higher metaphyta\n specially sensitive cells, or groups of cells, with a specific\n energy, are developed at certain points: sense-organs.\n\n 8th Stage: SENSATION OF THE LOWER METAZOA, without differentiated\n nerves or sense-organs. Lower c\u0153lenteria: sponges, polyps,\n platodaria.\n\n 9th Stage: SENSATION OF THE HIGHER METAZOA, with differentiated\n nerves and sense-organs, but still without consciousness(?). The\n higher c\u0153lenteria and most of the c\u0153lomaria.\n\n 10th Stage: SENSATION WITH DAWNING CONSCIOUSNESS, with independent\n formation of the phronema. The higher articulata (spiders and\n insects) and vertebrates (amphibia, lower reptiles, lower mammals).\n\n 11th Stage: SENSATION WITH CONSCIOUSNESS AND THOUGHT: amniotes:\n higher reptiles, birds, and mammals: savages.\n\n 12th Stage: SENSATION WITH PRODUCTIVE MENTAL ACTION IN ART AND\n SCIENCE: civilized men.\n\n\n\n\nXIV\n\nMENTAL LIFE\n\n Mind and soul--Intelligence and reason--Pure reason--Kant's\n dualism--Anthropology--Anthropogeny--Embryology of the mind--Mind of\n the embryo--The canonical mind--Legal rights of the embryo--Phylogeny\n of the mind--Paleontology of the mind--Psyche and phronema--Mental\n energy--Diseases of the mind--Mental powers--Conscious and\n unconscious mental life--Monistic and dualistic theory--Mental life\n of the mammals, of savages, and of civilized and educated people.\n\n\nThe greatest and most commanding of all the wonders of life is\nunquestionably the mind of man. That function of the human organism,\nto which we give the name of \"mind,\" is not only the chief source of\nall the higher enjoyment of life for ourselves, but it is also the\npower that most effectually separates man from the brute according\nto conventional beliefs. Hence it is supremely important for our\nbiological philosophy to devote a few careful pages to the study of its\nnature, its origin and development, and its relation to the body.\n\nAt the very outset of our psychological inquiry we are met by the\ndifficulty of giving a clear definition of \"mind,\" and distinguishing\nit from \"soul.\" Both ideas are extremely ambiguous: their content\nand connotation are described in the most various ways by the\nrepresentatives of science. Generally speaking, we mean by mind that\npart of the life of the soul which is connected with consciousness and\nthought, and is, therefore, only found in the higher animals which have\nintelligence and reason. In a narrower sense reason is regarded as the\nproper function of mind, and as the essential prerogative of man in the\nanimal world. In this sense Kant especially has done much to strengthen\nthe prevailing conception of mental action, and has, by his _Critique\nof Pure Reason_, converted philosophy into a mere \"science of reason.\"\nIn consequence of this conception, which still prevails widely in\nscientific circles, we will first study the mental life in the action\nof reason, and try to form a clear idea of this great wonder of life.\n\nPsychologists and metaphysicians are of very varied opinions as to\nthe difference between intelligence and reason. Schopenhauer, for\ninstance, considers causality to be the sole function of intelligence,\nand the formation of concepts to be the province of reason; in his\nopinion the latter power alone marks off man from the brute. However,\nthe power of abstraction, which collects the common features in a\nnumber of different presentations, is also found in the higher animals.\nIntelligent dogs not only discriminate between individual men, cats,\netc., according as they are sympathetic or the reverse, but they have\na general idea of man or cat, and behave very differently towards the\ntwo. On the other hand, the power of forming concepts is still so\nslight in uncivilized races that it rises but little above the mind of\ndogs, horses, etc.; the mental interval between them and civilized man\nis extremely wide. However, a long scale of reason unites the various\nstages of association of presentations which lead up to the formation\nof concepts; it is quite impossible to lay down a strict line of\ndemarcation between the lower and higher mental functions of animals,\nor between the latter and reason. Hence the distinction between the\ntwo cerebral functions is only relative; the intelligence comprises\nthe narrower circle of concrete and more proximate associations, while\nreason deals with the wider sphere of abstract and more comprehensive\ngroups of association. In the scientific life of the mind, therefore,\nthe intelligence is always occupied with empirical investigation, and\nreason with speculative knowledge. But the two faculties are equally\nfunctions of the phronema, and depend on the normal anatomic and\nchemical condition of this organ of thought.\n\nSince Kant won so great a prominence in modern philosophy for the\nidea of pure reason by his famous _Critique_ (1781), it has been much\ndiscussed, especially in the modern metaphysical theory of knowledge.\nIt has, however, like all other ideas, undergone considerable changes\nof meaning in the course of time. Kant himself at first understood\nby pure reason \"reason independent of all experience.\" But impartial\nmodern psychology based on the physiology of the brain and the\nphylogeny of its functions, has shown that there is no such thing as\nthis pure _a priori_ knowledge, independent of all experience. Those\nprinciples of reason which at present seem to be a priori in this sense\nhave been attained in virtue of thousands of experiences. In so far as\nthis is a question of real knowledge of the truth, Kant himself has\nfrequently recognized the point. He says expressly in his _Prolegomena\nto any future metaphysic that can be regarded as Science_ (1783, p.\n204): \"A knowledge of things by pure reason or pure intelligence is\nnothing but an empty appearance; only in experience is there truth.\"\nIn subscribing to this empirical theory of knowledge of Kant I. and\nrejecting the transcendental theory of Kant II., we may on our side\nunderstand by pure reason \"knowledge without prejudices,\" free from all\ndogma--all fictions of faith.\n\nThe familiar cry of modern metaphysicians, \"Return to Kant,\" has become\nso general in Germany that not only nearly all metaphysicians--the\nofficial representatives of \"philosophy\" at our universities--but\nalso many distinguished scientists, regard Kant's dualistic theory of\nknowledge as a necessary condition for the attainment of truth. Kant\ndominated philosophy in the nineteenth century much as Aristotle did\nin the Middle Ages. His authority became especially powerful when the\nprevailing Christian faith believed that his \"practical reason\" fully\nsupported its own three fundamental dogmas--the personality of God, the\nimmortality of the soul, and the freedom of the will. It overlooked\nthe fact that Kant had utterly failed to find proofs of these dogmas\nin his _Critique of Pure Reason_. Even conservative governments found\nfavorable features in this dualistic philosophy. We are, therefore,\nforced to return once more to this mischievous system; though Kant's\nantinomy of the two reasons has now been refuted so often and so\nthoroughly that we need not dwell any further on this point.\n\nAlthough the great K\u00f6nigsberg philosopher brought every side of\nhuman life within his comprehensive sphere of study, man remained to\nhim--as he had been to Plato and Aristotle, Christ and Descartes--a\ndual being, made up of a physical body and a transcendental mind or\nspirit. Comparative anatomy and evolution, which have provided the\nsolid morphological basis of monistic anthropology, did not come\ninto existence until the beginning of the nineteenth century; they\nwere quite unknown to Kant. He had, however, a presentiment of their\nimportance, as Fritz Schultze has shown in his interesting work on\n_Kant and Darwin_ (1875). We find in various places expressions which\nmay be described as anticipations of Darwinism. Kant also gave lectures\non \"Pragmatic Anthropology,\" and studied the psychology of races and\npeoples. It is remarkable that he did not arrive at a phylogenetic\nconception of the human mind, and a recognition of the possibility of\nits evolution from the mind of other vertebrates. It is clear that he\nwas held back from this by the profound mystic tendency of his theory\nof reason, and the dogma of the immortality of the soul, the freedom\nof the will, and the categorical imperative. Reason remained in Kant's\nview a transcendental phenomenon, and this dualistic error had a\ngreat influence on the whole structure of his philosophy. It must be\nremembered, of course, that our knowledge of the psychology of peoples\nwas then very imperfect; but a critical study of the facts then known\nshould have sufficed to convince him of the lower and animal condition\nof their minds. If Kant had had children, and followed patiently the\ndevelopment of the child's soul (as Preyer did a century later), he\nwould hardly have persisted in his erroneous idea that reason, with\nits power of attaining _a priori_ knowledge, is a transcendental and\nsupernatural wonder of life, or a unique gift to man from Heaven.\n\nThe root of the error is that Kant had no idea of the natural\nevolution of the mind. He did not employ the comparative and genetic\nmethods to which we owe the chief scientific achievements of the last\nhalf-century. Kant and his followers, who confined themselves almost\nexclusively to the introspective method or the self-observation of\ntheir own mind, regarded as the model of the human soul the highly\ndeveloped and versatile mind of the philosopher, and disregarded\naltogether the lower stages of mental life which we find in the child\nand the savage.\n\nThe immense advance made by the science of man in the second half\nof the nineteenth century cut the ground from under the older\nanthropology and the dualistic system of Kant. A number of newly\nfounded branches of science co-operated in the work. Comparative\nanatomy showed that our whole complicated frame resembles that of\nthe other mammals, and in particular differs only by slight stages\nof growth, and therefore in the details of the organs, from that\nof the anthropoid apes. The comparative histology of the brain\nespecially showed that this is also true of the brain, the real organ\nof mind. From comparative embryology we learned that man develops\nfrom a simple ovum just like the anthropoid ape; in fact, that it is\nalmost impossible to distinguish between the ape and the human embryo\neven at a late stage of development. Comparative animal chemistry\nexplained that the chemical compounds which build up our organs, and\nthe conversions of energy which accompany its metabolism, resemble\nthose in the other vertebrates. Comparative physiology taught us that\nall man's vital functions--nutrition and reproduction, movement and\nsensation--can be traced to the same physical laws in man as in all\nthe other vertebrates. Above all, the comparative and experimental\nstudy of the sense-organs and the various parts of the brain showed\nthat these organs of the mind work in the same way in man as in the\nother primates. Modern paleontology taught that man is, it is true,\nmore than a hundred thousand years old, but only appeared on earth\ntowards the close of the Tertiary Period. Prehistoric research and\ncomparative ethnology have shown that civilized nations were preceded\nby older and lower races, and these by savages, which have a close\nbodily and mental affinity to the apes. Finally, the reformed theory\nof descent (1859) enabled us to unite the chief results of the various\nbranches of anthropological study, and explain them phylogenetically\nby the development of man from other primates (anthropoid apes,\ncynocephali, lemures, etc.). By this means a new and monistic basis\nwas provided for modern anthropology; the position assigned to man in\nnature by dualistic metaphysics was shown to be utterly untenable. I\nhave attempted in the last edition of my _Anthropogeny_ (of which an\nEnglish edition is in preparation) to combine all these results of\nempirical investigation in a sketch of the natural evolution of man,\npaying special regard to embryology. I pointed out in chapters ii.-vi.\nof the _Riddle_ how important a part of our monistic philosophy this\nphylogenetic anthropology is.\n\nThe monistic conception of the human body and mind, which the theory\nof descent has put on a zoological basis, was bound to meet with the\nsternest resistance in dualistic and metaphysical circles. It was,\nhowever, also regarded with great disapproval by many modern empirical\nanthropologists, especially those who take it to be their chief\ntask to make as \"exact\" a study as possible of the human frame, and\nmeasure and describe its various parts. We might have expected these\ndescriptive anthropologists and ethnologists to extend a friendly\nhand to the new anthropogeny, and avail themselves of its leading\nideas, in order to bring unity and causal connection into the enormous\nmass of empirical material accumulated. However, this took place\nonly to a limited extent, The majority of anthropologists regarded\nevolution, and especially the evolution of man, as an undemonstrated\nhypothesis. They confined themselves to accumulating huge masses of\nraw empirical material, without having any clear aim or any definite\nquestions in view. This was chiefly the case in Germany, where the\nSociety of Anthropology and Prehistoric Research was for thirty years\nunder the lead of Rudolph Virchow. This famous scientist had won\ngreat honor in connection with the reform of medicine by his cellular\npathology and a number of distinguished works on pathological anatomy\nand histology since the middle of the nineteenth century. But when\nhe afterwards (subsequently to his removal to Berlin, 1856) devoted\nhimself chiefly to political and social questions, he lost sight of the\ngreat advance made in other branches of biology. He completely failed\nto appreciate its greatest achievement--the establishment of the\nscience of evolution by Darwin. To this we must add the psychological\nmetamorphosis (similar to that of Wundt, Baer, Dubois-Reymond, and\nothers), of which I have spoken in the sixth chapter of the _Riddle_.\nThe extraordinary authority of Virchow, and the indefatigable zeal\nwith which he struggled every year until his death (1903) against the\ndescent of man from other vertebrates, caused a wide-spread opposition\nto the doctrine of evolution. This was supported especially by Johannes\nRanke, of Munich, the secretary of the Anthropological Society.\nHappily, a change has recently set in. However, my _Anthropogeny_\nhas remained for thirty years the only work of its kind--namely, a\ncomprehensive treatment of man's ancestral history, especially in the\nlight of embryology.\n\nAs I pointed out in the eighth and ninth chapters of the _Riddle_, the\nmost solid foundation of our monistic psychology is the fact that the\nhuman mind grows. Like every other function of our organism, our mental\nactivity exhibits the phenomenon of development in two directions,\nindividually in each human being and phyletically in the whole race.\nThe ontogeny of the mind--or the embryology of the human soul--brings\nbefore us in direct observation the various stages of development\nthrough which the mind of every man passes from the beginning to the\nclose of life. The phylogeny of the mind--or the ancestral history of\nthe human soul--does not afford us this direct observation; it can only\nbe deduced by a comparison and synthesis of the historical indications\nwhich are supplied by history and prehistoric research on the one hand,\nand the critical study of the various stages of mental life in savages\nand the higher vertebrates on the other. In this the biogenetic law is\nused with great success (chapter xvi.).\n\nAs everybody knows, the new-born child shows as yet no trace of mind\nor reason or consciousness; these functions are wanting in it as\ncompletely as in the embryo from which it has been developed during\nthe nine months in the mother's womb. Even in the ninth month, when\nmost of the organs of the human embryo are formed and arranged as they\nappear later, there is no more trace of mind in its psychic life than\nin the ovum and spermatozoon from which it was evolved. The moment in\nwhich these sexual cells unite marks precisely the real commencement of\nindividual existence, and therefore of the soul also (as a potential\nfunction of the plasm). But the mind proper--or reason, the higher\nconscious function of the soul--only develops, slowly and gradually,\nlong after birth. As Flechsig has shown anatomically, the cortex in the\nnew-born child is not yet organized or capable of functioning. Rational\nconsciousness is even impossible for the child when it begins to speak;\nit reveals itself for the first time (after the first year) at the\nmoment when the child speaks of itself, not in the-third person, but\nas \"I.\" With this self-consciousness comes also the antithesis of the\nindividual to the outer world, or world-consciousness. This is the real\nbeginning of mental life.\n\nIn defining the appearance of the individual mind by the awakening\nof self-consciousness, we make it possible to distinguish, from the\nmonistic physiological point of view, between \"soul\" (_psyche_) and\n\"spirit\" (_pneuma_). There is a soul even in the maternal ovum and\nthe paternal spermatozoon (_cf._ chapter xi.); there is an individual\nsoul in the stem-cell (_cytula_) which arises at conception by the\nblending of the parent cells. But the mind proper, the thinking reason,\ndevelops out of the animal intelligence (or earlier instincts) of the\nchild only with the consciousness of its personality as opposed to the\nouter world. At the same time the child reaches the higher stage of\npersonality, which law has for a long time taken under its protection\nand made morally responsible to society by education. This shows how\nerroneous and untenable, from the physiological point of view, are the\nideas still embodied in our code as to the psychic life and the mind of\nthe embryo and the new-born infant. They came mostly from the canon law\nof the Catholic Church.\n\nThe dualistic ideas of the soul of the human embryo which were taught\nby the Church in the Middle Ages are particularly interesting from\nthe psychological point of view; and at the same time they are of\ngreat practical importance even in our own day, since many of their\nmoral consequences form an important element in canon law, and have\npassed from this into civil law. This influential canon law was formed\nunder ecclesiastical authority from the decisions of Church councils\nand the decretals of the popes. It is, like most of the dogmas and\ndecrees which civilization owes to this powerful hierarchy, a curious\ntissue of old traditions and new fictions, political dogmas, and\ncrass superstition. It is directed to the despotic ruling of the\nuneducated masses and the exclusive dominion of the Church--a Church\nthat calls itself Christian while thus acting as the very reverse of\npure Christianity. The canon law takes its name from the dogmatic rules\n(or canons) of the Church. They involuntarily suggest the metal tubes\nwhich are so often the _ultima ratio regis_ in the wars of Christian\nnations. The canonical regulations of the Church, as implements of a\ncrude spiritual despotism, have no more to do with the ethical laws\nof pure reason than the cannons of secular authorities have as naked\norgans of physical force. We might write the motto, _Ultima ratio\necclesi\u00e6_ (the last argument of the Church), over the sacred _Corpus\nJuris Canonici_. A collection of later papal decretals which forms an\nappendix to the books of canon law was very happily given the official\ntitle of _Extravagantes_. Among the \"extravagant\" nonsense which the\npapacy included in canon law as a moral code for believers is its view\nof the psychic life of the embryo. The \"immortal soul\" is supposed\nto enter the soulless embryo only several weeks after conception. As\ntheologians and metaphysicians are very much divided as to the period\nof this entrance of the soul, and know nothing about the structure of\nthe embryo and its development, we will only recall the fact that the\nhuman f\u0153tus cannot be distinguished from that of the anthropoid\nape and other mammals even in the sixth week of its development. The\noutline of the five cerebral vesicles and the three higher sense-organs\n(nose, eye, and ear vesicle) is discernible in the head; the two\npairs of limbs can be traced in the shape of four simple roundish\nunjointed plates; and the pointed tail sticks out at the lower part,\nthe rudimentary legacy from our long-tailed ape-ancestors. Although the\ncortex is not yet developed at this stage, the embryo may be considered\nto have a \"soul\" (_cf._ chapters xiv. and xv. of my _Anthropogeny_, and\nplates 8-14).\n\nIt is said to be a great merit of canon law that it was the first to\nextend legal protection to the human embryo, and punished abortion\nwith death as a mortal sin. But as this mystical theory of the\nentrance of the soul is now scientifically untenable, we should expect\nthem consistently to extend this protection to the f\u0153tus in its\nearlier stages, if not to the ovum itself. The ovary of a mature maid\ncontains about 70,000 ova; each of these might be developed into a\nhuman being under favorable circumstances if it united with a male\nspermium after its release from the ovary. If the state is so eager\nfor the multiplication of its citizens in the general interest, and\nregards prolific reproduction as a \"duty\" of its members, this is\ncertainly a \"sin of omission.\" It punishes abortion with several\nyears' imprisonment. But while civil law thus takes its inspiration\nfrom canon law, it overlooks the physiological fact that the ovum is\na part of the mother's body over which she has full right of control;\nand that the embryo that develops from it, as well as the new-born\nchild, is quite unconscious, or is a purely \"reflex machine,\" like\nany other vertebrate. There is no mind in it as yet; it only appears\nafter the first year, when its organ, the phronema in the cortex, is\ndifferentiated. This interesting fact is explained by the biogenetic\nlaw, which shows that the ontogeny of the brain is a condensed\nrecapitulation of its phylogeny in virtue of the laws of heredity.\n\nThe biogenetic law applies just as much to the brain, the organ of\nmind, as to any other organ of the human body. On the strength of the\nontogenetic facts, which fall under direct observation, we infer that\nthere was a corresponding development in the phylogenetic series of\nour animal ancestors. A significant confirmation of this inference is\nfound in comparative anatomy. It shows that in all the skull-animals\n(_craniota_)--from the fishes and amphibia up to the apes and man--the\nbrain is developed in the same way, as a vesicular distension of\nthe ectodermal medullary tube. This simple oval cerebral vesicle\nfirst divides into three and afterwards five successive vesicles by\ntransverse constriction (_Anthropogeny_, chapter xxiv., plate 24). It\nis the first of these vesicles, the cerebrum, that afterwards becomes\nthe chemical laboratory of the mind. In the lower craniota (fishes and\namphibia) the cerebrum remains very small and simple. It only reaches\na notably higher stage in the three chief classes of the vertebrates,\nthe amniotes. As these land-dwelling and air-breathing craniota have\nmore difficult work to do in the struggle for life than their lower\naquatic ancestors, we find much more varied and complex habits among\nthem. These hereditary habits are gradually converted into instincts by\nfunctional adaptation and progressive heredity; and with the further\ndevelopment of consciousness in the higher mammals we have at last\nthe appearance of reason. The gradual unfolding of the mental life is\naccompanied step by step with the advance of its anatomic organ, the\nphronema in the cortex. Recent careful investigations of the ontogeny\nand histology of the origin of mind (by Flechsig, Hitzig, Edinger,\nZiehen, Oscar Vogt, etc.) have given us an interesting insight into the\nmysterious processes of its phylogeny.\n\nWhile the comparative anatomy of the cortex gives us a good idea\nof the gradual historical development of the mind in the higher\nclasses of vertebrates, we get at the same time from their fossilized\nremains positive indications as to the period of time in which this\nphylogenesis has slowly taken place. The historical series in which the\nclasses of vertebrates have succeeded each other in the great periods\nof the organic history of the earth is directly demonstrated by their\nfossil remains--the real commemorative medals of natural creation--and\ngives us a most valuable record of the ancestral history of our race\nand of the mind. The oldest strata that contain vertebrate remains\nform the huge Silurian System, which were, on the latest calculations,\nformed more than a hundred million years ago. They contain a few fossil\nfishes. In the succeeding Devonian System these are followed by the\ndipneusta, transitional forms between the fishes and the amphibia. The\nlatter, the oldest four-footed and five-toed vertebrates, appear in\nthe Carboniferous Period. They are succeeded in the Permian, the next\nsystem, by the oldest amniotes, the primitive reptiles (tocosauria).\nIt is not until the next period (the Triassic) that the oldest mammals\nare found, small primitive monotremes (_pantotheria_), then marsupials\nin the Jurassic, and the first placentals in the Cretaceans. The great\nwealth of varied and highly organized forms which are contained in this\nthird and last sub-class of the mammals appear only in the succeeding\nTertiary Period. The numbers of well-preserved skulls which these\nplacentals have left behind in fossil form are particularly important,\nbecause they give us an idea of the quantitative and qualitative\nformation of the brain within the various orders; thus, for instance,\nin the modern carnivora the brain is from two to four times, and in the\nmodern ungulates from six to eight times, as large (in proportion to\nthe size of the body) as in their earliest Tertiary ancestors. It is\nalso found that the cortex (the real organ of mind) has developed in\nthe Tertiary Period at the expense of the other parts of the brain. The\nduration of this C\u00e6nozoic Period has lately been calculated at three\nmillion years (according to other geologists twelve to fourteen or more\nmillion years). It was, at all events, sufficient to make possible the\ngradual development of the human mind from the lower intelligence of\nour ape-ancestors and the instincts of the older placentalia.\n\nWe have given the physiological name of the \"phronema,\" as the real\norgan of mind or the instrument of reason, to that part of the cortex\non the normal anatomic condition of which the action of the human mind\ndepends. The remarkable investigations during the last few decades of\nthe finer texture of the grey cortex (or cortical substance of the\ncerebrum) have shown that its structure--a real anatomic \"wonder of\nlife\"--represents the most perfect morphological product of plasm;\nand its physiological function--mind--is the most perfect action of\na \"dynamo-machine,\" the highest achievement that we know anywhere\nin nature. Millions of psychic cells or neurona--each of them of an\nextremely elaborate fibril molecular structure--are associated as\nspecial thought-organs (phroneta) at certain parts of the cortex, and\nthese again are built up into a large harmonious system of wonderful\nregularity and capacity. Each phronetal cell is a small chemical\nlaboratory, contributing its share to the unified central function of\nthe mind, the conscious action of reason. Scientists are still very far\nfrom agreement as to the extent of the phronema in the cortex and its\ndelimitation from the neighboring sense-centres (sensoria). But they\nare all agreed that there is such a central organ of mind, and that its\nnormal anatomic and chemical condition is the first requisite for the\nlife of the human mind. This belief--one of the foundations of monistic\npsychology--is confirmed by the study of psychiatry.\n\nThe study of the diseased organism has greatly furthered our knowledge\nof the normal frame. Diseases are so many physiological experiments\nmade by nature herself under special conditions, which experimental\nphysiology would often be unable to arrange artificially. The\nthoughtful physician or pathologist can often obtain most important\nknowledge of the function of organs by carefully observing them during\ndisease. This is especially true of diseases of the mind, which\nalways have their immediate foundation in an anatomical or chemical\nmodification of certain parts of the brain. Our advancing knowledge\nof the localization of mental functions, or of their connection with\nspecial phroneta or organs of thought, is for the most part based on\nthe experience that the destruction of the one is followed by the\nextinction of the other. Modern psychiatry, the empirical science of\nmental disease, has thus become an important element of our monistic\npsychology. If Immanuel Kant had studied it and had visited the\nasylum wards for a few months, he would certainly have escaped the\ndualist errors of his philosophy. We may say the same of the modern\nmetaphysical psychologists who built up a mystic theory of an immortal\nsoul without knowing the anatomy, physiology, and pathology of the\nbrain.\n\nThe comparative anatomy, physiology, and pathology of the brain, in\nconcurrence with the results of ontogeny and phylogeny, have led\nus to form the sound monistic principle that the human mind is a\nfunction of the phronema, and that the neurona of the latter, or the\nphronetal cells, are the real elementary organs of mental life. Hence\nmodern energism is perfectly justified in regarding mental energy\n(in all its forms) from the same point of view as all other forms of\nnervous energy, and in fact all manifestations of energy in organic\nor inorganic nature. Fechner's psychophysics had already shown that a\npart of this nervous energy is measurable and mathematically reducible\nto the mechanical laws of physics (_Riddle_, chapter vi.) Ostwald\nhas, in his _Natural Philosophy_, lately emphasized the fact that all\nthe manifestations of mental life, not only sensation and will, but\neven thought and consciousness, can be reduced to nervous energy.\nHence we may distinguish what are called mental forces from the other\nexpressions of nervous energy as _phronetic energy_. The monistic\nresearch of Ostwald on the energy-processes in mental life (chapter\nxviii.), consciousness (chapter xix.), and will (chapter xx.) is very\nnotable, and confirms the views I advanced in the second part of the\n_Riddle_ (chapters vi., x., and xi.). Ostwald has, however, caused\nsome misunderstanding by insisting on substituting his idea of energy\nfor the pure notion of substance (as Spinoza had formulated it), and\nby rejecting the other attribute of substance, matter. His supposed\n\"Refutation of Materialism\" is a mere attack on windmills; his energism\n(the consistent dynamism of Leibnitz, etc.) is just as one-sided as its\napparent opposite, the consistent materialism of Democritus, Holbach,\netc. The latter makes matter precede force; the former regards matter\nas the product of force. Monism escapes the one-sidedness of both\nsystems, and, as hylozoism, refuses to separate the two attributes of\nsubstance, space-filling matter and active energy. This applies to\nmental life just as to any other natural process; our mental forces or\nphronetic energies are just as much bound up with the neuroplasm, the\nliving plasm of the neurona in the cortex, as the mechanical energy\nof our muscles is with the contractile myoplasm, the living muscular\nsubstance.\n\nIn the exhaustive study of consciousness which I gave in the tenth\nchapter of the _Riddle_ I sought to show that this enigmatic\nfunction--the central mystery of psychology--is not a transcendental\nproblem, but a natural phenomenon, subject to the law of substance,\nas much as any other psychic power. The child's consciousness only\ndevelops long after its first year, and grows as gradually as any other\npsychic function; like these, it is bound up with the normal anatomic\nand chemical condition of its organs, the phroneta in the cortex.\nConsciousness develops originally out of unconscious functions (as an\n\"inner view,\" or mirroring, of the action of the phronema); and at any\ntime an unconscious process in the cortex may come within the sphere\nof consciousness by having the attention directed to it. On the other\nhand, conscious actions, which need a good deal of attention when they\nare first learned (such as playing the piano), may become unconscious\nthrough frequent repetition and practice. The fact that chemical energy\nis converted in the phronetal cells during any of these actions is\nproved by the fatigue and exhaustion which prolonged mental work causes\nin the brain, just as mechanical work does in the muscles. Fresh matter\nhas to be supplied by the food before the mental work can be continued.\nMoreover, it is well known that various drinks have a considerable\ninfluence on consciousness (coffee and tea, beer and wine); and the\ntemporary extinction of it under chloroform or ether is an analogous\nfact. Again, the familiar phenomena of the dream, the deviations from\nnormal consciousness, hallucinations, delusions, etc., must convince\nevery impartial thinker that these mental functions are not of a\nmetaphysical character, but physical processes in the neuroplasm of the\nbrain, and thoroughly dependent on the law of substance.\n\nIn complete contrast to this natural monistic conception of the\nhuman mind, which is, in my opinion, definitely established by\nnineteenth-century science, we have the older dualistic estimate of\nit which is still widely accepted both by unlearned and learned,\nespecially metaphysicians and theologians. I have already dealt in\nthe _Riddle_ (chapter xi.) with the grounds for this belief in an\nimmaterial soul, and expressed my conviction that \"the belief in the\nimmortality of the human soul is in flagrant contradiction to the\nsoundest empirical principles of modern science.\" I must refer the\nreader to what I said there about thanatism and athanatism, only\nreminding him once more of the immense influence of the Kantist\nphilosophy in maintaining this belief in the spirituality of the\nsoul. Kant derived from the introspective study of his own gifted\nmind an extremely high estimate of human reason, and he fallaciously\ntransferred this estimate to the human mind generally. He did not\nperceive that it is either wholly wanting in the savage, or does not\nrise much above the stage which has been reached by the intelligence of\nthe dog, horse, elephant, and other advanced animals.\n\nModern anthropogeny has raised the theory of evolution to the rank of\nan historical fact. All the various organs of our body resemble those\nof our nearest relatives, the anthropoid apes, in their structure and\ncomposition. They only differ from them in details of form and size,\nwhich are determined by inherited variations of growth. But the\nfunctions as well as the organs have been inherited by man from his\nprimate ancestors. This applies to the mind also, which is merely the\ncollective function of the phronema, the central organ of thought.\nAn impartial comparison of mental life in the anthropoid ape and\nthe savage shows that the differences between the two are not more\nconsiderable than the differences in the structure of their brains.\nHence, if one accepts the dualistic theory of the soul formulated by\nPlato and Kant and accepted by so many modern psychologists, it is\nnecessary to attribute an immortal soul to the anthropoid apes and the\nhigher mammals (especially to domestic dogs) just as well as to savage\nor civilized man (_cf._ chapter xi. of the _Riddle_).\n\nThe thorough and careful study of the mental life of the savage,\nsupported by the results of anthropogeny and ethnography, has in the\ncourse of the last forty years decided the issue of this struggle\nbetween the conflicting theories of the origin of civilization. The\nolder theory of degeneration, based on religious beliefs, and so\npreferred by theologians and theosophists, declared that man--the\n\"image of God\"--was created originally with perfect bodily and mental\npowers, and only fell away from his high estate after the original\nsin. On this view the present savages are degenerate descendants of\nthe first godlike men. (In tropical lands the anthropoid apes are in\nsimilar fashion regarded by the natives as degenerate branches of\ntheir own stem!) Although this Biblical degeneration theory is still\ntaught in most of our schools, and even supported by a few mystic\nphilosophers, it had lost all scientific countenance before the end\nof the nineteenth century. It is now replaced by the modern theory\nof evolution, which was represented by Lamarck, Goethe, and Herder\na century ago, and raised to a predominant position in ethnography\nby Darwin and Lubbock. It has taught us that human civilization is\nthe outcome of a long and gradual process of evolution, covering\nthousands of years. The civilized races of our time have arisen from\nless civilized races, and these in turn from lower, until we reach the\nsavage races which show no trace of civilization.\n\nEthnologists distinguish as a separate class the races which are found\nmidway between the civilized peoples and the savages. We shall deal\nwith their classification and characteristics later on (chapter xvii.).\nThese races show some advance on the artistic instinct which we find in\na slight degree even among the savages at times; moreover, their animal\ncuriosity develops into human curiosity, and raises the question of the\ncauses of phenomena, the germ of all science.\n\nCivilized races, which occupy the next stage to these, are raised above\nthem by the formation of larger states and a greater division of labor.\nThe specialization of the various groups of workers and the greater\nease of maintenance permit a further development of art and science. To\nthese groups belong, of living races, the majority of the Mongolians,\nand the greater part of the inhabitants of Europe and Asia in ancient\nand medi\u00e6val times. The great ancient civilizations of China, Southern\nIndia, Asia Minor, Egypt, and afterwards of Greece and Italy, show not\nonly a great development of art and science, but also a concern for\nlegislation, religious worship, education of the young, and the spread\nof knowledge by written books.\n\nCivilization in the narrower sense, characterized by a high development\nof art and science and the manifold application of them to practical\nlife in legislation, education, etc., was greatly advanced even in\nantiquity among several nations--in Asia by the Chinese, Southern\nIndians, Babylonians, and Egyptians; in Europe by the Greeks and Romans\nof the classic age. However, their results were at first restricted\nto narrow fields, and were mostly lost during the Middle Ages. Modern\ncivilization rose to importance about the end of the fifteenth century,\nwhen the invention of printing had made possible the spread of\nknowledge far and wide, the discovery of America and circumnavigation\nof the globe had widened the horizon, and the Copernican system had\ndemolished the error of geocentricism. Then began the many-sided\ngrowth of civilization which has reached so marvellous a height in the\nnineteenth century through the extraordinary development of science.\nThen at last free reason could triumph over the prevailing medi\u00e6val\nsuperstition.\n\n\n\n\nXV\n\nTHE ORIGIN OF LIFE\n\n\n The miracle of the origin of life--Creation of species: Moses and\n Agassiz--Creation of the first cells: Wigand and Reinke--Agnostic\n position: resignation--Eternity hypothesis (dualistic, Helmholtz;\n monistic, Preyer)--Archigony hypothesis (autogony hypothesis,\n Haeckel, N\u00e4geli; cyanic hypothesis, Pfl\u00fcger, Verworn)--Spontaneous\n generation--Saprobiosis or necrobiosis--Experiments in spontaneous\n generation--Pasteur--Stages of archigony--Observation of\n archigony--Synthesis of plasma--Value of the unsuccessful experiments\n to produce plasm artificially--The logic of modern experimental\n biology.\n\n\nThe question of the origin of life is one of the most important and\ninteresting, but one of the most difficult and complicated, problems\nwith which the mind of man has been occupied for thousands of years.\nThere are few other questions (such as the freedom of the will or\npersonal immortality) on which such different and contradictory views\nhave been expressed, and few that remain so far from being closed\nat the present day. There are, moreover, few problems on which the\nopinions of even distinguished thinkers diverge so much, and have\ndegenerated so much into fantastic hypotheses. This is partly due to\nthe extreme difficulty of giving a strictly scientific solution of\nthe problem and partly to the confusion of ideas which is so great in\nthis controversy, the lack of clear rational insight, and the powerful\nauthority of the prevailing religious faith and other venerable dogmas.\n\nThe easiest and quickest thing to do is to cut the Gordian knot of\nthe question with the sword of faith, or answer it with a belief in\na supernatural creation. The first article of the creed was given\nto us in childhood as the foundation of all cosmic philosophy. It\nis based on the Mosaic account of creation in the first chapter of\nGenesis. As I have fully examined its scientific value in the second\nchapter of my _History of Creation_, I may refer the reader thereto.\nIt is unquestionable that this myth still has a very great practical\ninfluence; the great majority of the clergy cling to it because it is\nfound in the infallible \"word of God.\" Most governments, which hold\nblind faith to be an important element of education, include it in the\ncode for the elementary school. On the other hand, it is difficult\nto find a man of science who will uphold it to-day. The gifted Louis\nAgassiz made one of the most remarkable attempts to do this in\nhis _Essay on Classification_ (1858), a book that appeared almost\ncontemporaneously with Darwin's epoch-making _Origin of Species_, and\ndealt with the general problems of biology from the directly opposite,\nthe mystic, point of view. According to Agassiz, each species of animal\nor plant is an \"incarnate thought of the Creator.\"\n\nDiffering from this Biblical fancy of the supernatural creation of\neach species, two botanists, Wigand of Marburg and Reinke of Kiel,\nhave lately restricted the action of the celestial architect very\nconsiderably; they have ascribed to him only the creation of the\nprimitive cells, which he is supposed to have endowed with the power\nto develop into the higher organisms. Wigand assumed for the origin\nof each species a special primitive cell and a long phylogenetic\ndevelopment of this; Reinke prefers a stem, composed of a number of\nspecies. These modern creative theories have no more scientific value\nthan that of Agassiz; they are equally based on pure superstition\n(_cf._ chapters i.-iii.).\n\nA different attitude from this irrational positive superstition is\nthe sceptical view of those scientists who regard the question of the\norigin of life as insoluble or transcendental. Darwin and Virchow are\nrepresentatives of this agnostic position; they held that we know\nnothing, and can know nothing, about the origin of the first organisms.\nDarwin, for instance, explains in his chief work that he \"has nothing\nto do with the origin of the fundamental spiritual forces, or with\nthat of life itself.\" This is a complete abandonment of the task of\nsolving a scientific problem which must present as definite a subject\nof inquiry to modern research as any other evolutionary problem. The\norigin of life on our planet represents a fixed point in its history.\nHowever, there is nothing to be said if a scientist chooses to make no\ninquiry into it. A number of distinguished modern scientists maintain\nthis agnostic attitude; they are more or less convinced that the origin\nof life is a natural process, but believe we have not as yet the means\nto explain it.\n\nDifferent, again, is a third attitude which regards the problem of\nthe origin of life as extremely difficult, yet capable of solution.\nThis is the position of Dubois-Reymond, for instance, who counts the\norigin of life as the third great cosmic problem. Most of the modern\nscientists who have worked on the problem are of this opinion, although\ntheir views as to the way of solving it differ very much. We are\nconfronted, in the first place, with two essentially different views\nwhich we may call the eternity-hypothesis and the theory of archigony\n(or spontaneous generation). According to the first view, organic life\nis eternal; according to the second, it began at a definite point of\ntime. The eternity-hypothesis has assumed two very different forms, one\nof which has a dualistic and the other a monistic base. Helmholtz is a\nrepresentative of the former theory, and Preyer of the latter.\n\nHermann Eberhard Richter put forward, in 1865, the hypothesis that\ninfinite space is full throughout of the germs of living things,\njust as it is of inorganic bodies; both of them are in a condition\nof eternal development. When the ubiquitous germs reach a mature and\nhabitable cosmic body, which possesses heat and moisture in the proper\ndegrees for their development, they break into life, and may lead to\nthe formation of a whole world of living things. Richter conceives\nthese ubiquitous germs as living cells, and formulates the principle:\n_Omne vivum ab \u00e6ternitate e cellula_ (Every living thing is eternal and\nfrom a cell). In much the same way the botanist Anton Kerner postulates\nthe eternity of organic life and its complete independence of the\ninorganic world. But the difficulties encountered by this hypothesis,\nin the indefinite form that Kerner gives it, are so great and so\nobvious that his theory has won no recognition.\n\nHowever, the \"cosmozoic hypothesis\" attained a great popularity when it\nwas afterwards taken up by two of the most distinguished physicists,\nHermann Helmholtz and Sir W. Thomson (Lord Kelvin). Helmholtz\nformulated the alternative thus (in 1884): \"Organic life either came\ninto existence at a certain period, or it is eternal.\" He declared for\nthe latter view, on the ground that we have not succeeded in producing\nliving organisms by artificial means. He supposes that the meteors\nthat roam about the universe might contain the germs of organisms,\nand, under favorable conditions, these might reach the earth or other\nplanets and develop thereon. This cosmozoic hypothesis of Helmholtz\nis untenable, because the physical features of space (the extreme\ntemperatures, the absolute dryness, the absence of atmosphere, etc.)\nexclude the lasting existence of plasm on meteorites in the form of\norganic germs with a capacity to live. The hypothesis is, moreover,\nlogically useless, since it does not solve, but postpones, the\nquestion of the origin of organic life. If it is consistently worked\nout, it leads to pure cosmological dualism.\n\nAnother and very different theory of the eternity of life has been\nelaborated by Theodor Fechner (1873) and Wilhelm Preyer (1880). Both\nthese scientists extend the idea of life to the whole cosmos, and\nreject the distinction that is usually drawn between the organic and\nthe inorganic. Fechner goes so far as to ascribe consciousness to the\nwhole universe and every single body in it, and regards individual\norganisms merely as parts of one vast universal organism. His system\nis, therefore, panpsychistic, and, at the same time, pantheistic, as he\nsomewhat mystically connects the idea of a conscious God with that of\na living universe. Preyer generally agrees with him in extending the\nidea of life to the whole universe, and conceiving it as an organism.\nHe applies his theory in the symbolic sense which I alluded to on page\n38, and described as impracticable. The fiery mass of the forming\nearth is the gigantic organism, and Preyer gives the name of \"life\" to\nits rotatory movement (or gravitational energy). As it cooled down,\nthe heavier metals (the dead inorganic masses) separated from it;\nfrom the rest of it were formed first simple and afterwards complex\ncarbon-combinations, and finally albumin and plasm. This extension\nof the word \"organism\" has very properly met with little approval in\nbiology. It only increases the confusion, and the difficulty of marking\noff biological from abiological science, which is both practically\nnecessary and theoretically justified.\n\nIf, then, in our opinion, the eternity-hypotheses are of no more\nvalue than the creation-hypotheses, we have left, for the purpose of\nanswering the great question of the origin of life, only the third\ngroup of scientific theories which I have combined under the general\nhead or archigony. They start from the following points: 1. Organic\nlife is everywhere bound up with the plasm (or protoplasm), a chemical\nsubstance of a viscous character, having albuminous matter and water as\nits chief constituents. 2. The characteristic movements of this living\nsubstance, to which we give the name of organic life, are physical and\nchemical processes, that can only take place within certain limits of\ntemperature (between the freezing-point and boiling-point of water).\n3. Beyond these limits organic life may in certain circumstances be\nmaintained for a time in a latent condition (apparent death, potential\nlife); but this latent condition is restricted to a certain (and\ngenerally short) period. 4. As the earth, like all the other planets,\nwas for a long time in a state of incandescence, at a temperature\nof several thousand degrees, living organisms (viscous albuminoids)\ncannot possibly have existed on it, and so cannot be eternal. 5.\nFluid water, the first condition for the appearance of organic life,\ncannot have formed on it until the crust at the surface had fallen\nbelow boiling-point. 6. The chemical processes which first set in\nat this stage of development must have been catalyses, which led to\nthe formation of albuminous combinations, and eventually of plasm.\n7. The earliest organisms to be thus formed can only have been\nplasmodomous monera, structureless organisms without organs; the\nfirst forms in which the living matter individualized were probably\nhomogeneous globules of plasm, like certain of the actual chromacea\n(_chroococcus_). 8. The first cells were developed secondarily from\nthese primitive monera, by separation of the central caryoplasm\n(nucleus) and peripheral cytoplasm (cell-body).\n\nThe monistic hypothesis of abiogenesis, or autogony (=\nself-development) in the strictly scientific sense of the word, was\nfirst formulated by me in 1866 in the second book of the _General\nMorphology_. The solid foundation for it was found in the monera I had\ndescribed, the very simple organisms without organs that had up to that\ntime been overlooked or thrust aside. It is of radical importance, in\ngiving a naturalistic solution of the problem of the origin of life, to\nstart from these structureless granules of living matter, and not--as\nstill generally happens--from the cell; these nucleated elementary\norganisms could not be the earliest archigonous living things, but\nmust have been evolved secondarily from the unnucleated monera. Hence,\nI made a very thorough study of these rudimentary organisms in my\n_Monograph on the Monera_ (1870), and endeavored to formulate it more\nclearly later on (in the first volume of the _Systematic Phylogeny_).\nIn regard to the chemical question of the first formation of plasm\nand its inorganic preparation, Edward Pfl\u00fcger conducted some valuable\ninvestigations, and recognized that the radical of cyanogen was the\nchief element of the living plasm. I may therefore distinguish two\ndifferent stages of the theory--my own older autogony-hypothesis and\nthe later cyanogen-hypothesis.\n\nThe theory of abiogenesis, or archigony, which I advanced in 1866, and\nhave developed in later writings, appeals directly to the biochemical\nfacts that modern vegetal physiology has firmly established. The\nchief of these facts is that even the living green plant-cell has the\nsynthetic faculty of plasmodomism or carbon-assimilation; that is to\nsay, it is able to build up, by a chemical synthesis and reduction,\nfrom simple inorganic compounds (water, carbonic acid, nitric acid,\nand ammonia), the complex albuminous compounds which we call plasm\nor protoplasm, and which we regard as the active living substance\nand the true material basis of all vital function (_cf._ chapter\nvi.). All botanists are now agreed that this most important process\nof vegetal life, the fundamental process of all organic life and all\norganization, is a purely chemical (or, in the wider sense, physical)\nprocess, and that there is no question of a specific vital force or a\nmystic constructor (like the famous \"mechanical engineer of life\"),\nor any other transcendental agency, in connection with it. The tiny\nchemical laboratory in which this remarkable organoplastic process\ntakes place under the influence of sunlight is, in the simplest\nplants, the chromacea, either the whole homogeneous globule of plasm\n(_chroococcus_) or its bluish-green surface-layer, which is active\nas a chromatic principle (chromatophore). But in most plants these\nreduction-laboratories are the chromatella or chromatophora, which\nhave been differentiated from the rest of the plasm of the cell, and\nare colorless globular leucoplasts within its dark interior, or green\nchromoplasts (or granules of chlorophyll) at its illumined surface.\nMy theory of archigony only assumes that this chemical process of\nplasmodomism which we find repeated every second in every plant-cell\nexposed to the sunlight, and which has become an \"inherited habit\" of\nthe green plant-cell, developed of itself at the beginning of organic\nlife; in other words, it is a catalytic process (or one analogous to\ncatalysis), the physical and chemical conditions of which were present\nin the condition of organic nature at that time.\n\nMy hypothesis was very strongly confirmed twenty years ago by the\nadhesion of the able botanist, Carl N\u00e4geli. In his instructive work,\n_A Mechanical-physiological Theory of Evolution_ (1884), he supported\nall the principal ideas as to the natural origin of life which I\nhad advanced in 1866. He formulates the chief part of them in this\nadmirable principle:\n\n The origin of the organic from the inorganic is, in the first place,\n not a question of experience and experiment, but a fact deduced from\n the law of the constancy of matter and force. If all things in the\n material world are causally related, if all phenomena proceed on\n natural principles, organisms, which are formed of and decay into\n the same matter, must have been derived originally from inorganic\n compounds.\n\nThis excellent and clear declaration of a distinguished scientist and\nprofound thinker might be taken to heart by the \"exact\" scientists who\nare always attacking the monistic theory of archigony as an unproved\nhypothesis, or regard the whole problem as insoluble. N\u00e4geli has,\nmoreover, proceeded to make a thorough study of the molecular processes\ninvolved, and embodied the results in his idioplasm theory. He\nbelieves that at the beginning of organization the definite autonomous\narrangement of the smallest homogeneous parts of the plasm was a\nmatter of the greatest importance. In his opinion these \"micella\" are\ncrystalline groups of molecules, arranged multifariously in strings and\nparallel rows.\n\nA similar and more elaborate attempt to give a physical explanation\nof the processes of archigony and trace them to mechanical molecular\nstructures was made by Ludwig Zehnder in 1899 in his work on _The\nOrigin of Life_. He believes that the smallest and lowest life-unities\n(the micellar strings of N\u00e4geli and the biophora of Weismann,\ncorresponding to my plastidules) have a tubular shape, and so he calls\nthem \"fistella.\" He supposes that these invisible molecular structures\nare regularly arranged in millions in the plasma of the cell, and\ndifferentiated in such a way that some will effect endosmosis, others\ncontraction, others the conduction of stimuli, and so on. As in\nthe similar work of N\u00e4geli and others, the value of this molecular\nhypothesis is that it stimulates us to attempt to conceive the mode of\nthe arrangement and movement of the molecules of plasm in the process\nof archigony on physical principles.\n\nA more interesting and notable attempt to penetrate into the mysterious\nobscurity of the chemical processes in archigony was made in 1875\nby the distinguished physiologist, Edward Pfl\u00fcger, in his essay on\n_Physiological Combustion in the Living Organism_. He starts from\nthe fact that the plasm (or protoplasm) is the material basis of all\nvital phenomena, and that this living matter owes its properties to\nthe chemical properties of the albumin (whether we regard this as a\nchemical unity, protein or protalbumin, or as a mixture of different\ncompounds). However, Pfl\u00fcger sharply distinguishes between the living\nalbumin of the plasm out of which all organisms are built, and the dead\nalbumin, such as we find it, for instance, in the glairy albumin of the\nhen's egg. Only the living albumin (plasm) decomposes of itself in a\nslight degree, and to a greater extent under the influence of external\nexcitation; the dead albumin will remain intact for a long time under\nfavorable conditions. The cause of the extraordinary instability of the\nliving albumin is its intramolecular oxygen--that is to say, the oxygen\nthat is taken into the interior of the plasma-molecules in breathing,\nand effects there a disassociation, surrounding the atoms and breaking\nup the new-formed groups.\n\nThe real cause of this rapid decomposability of the plasm, and of the\naccompanying formation of carbonic acid, is found in the cyanogen,\na remarkable body composed of an atom of carbon and an atom of\nnitrogen, which, in conjunction with potassium, forms the well-known\nand very virulent poison, cyanide of potassium. The non-nitrogenous\ndecomposition-products of the dead and the living albumin agree in the\nmain, but their nitrogenous products are totally different. Uric acid,\ncreotin, guanine, and the other decomposition products of plasm contain\nthe cyanogen-radical, and the most important of all, urea, can be\nartificially produced from cyanic compounds, as W\u00f6hler showed in 1828.\nFrom this we may infer that the living albumin always contains the\ncyanogen-radical, and that dead nutritive albumin does not. The belief\nthat it is cyanogen which gives its characteristic vital properties\nto the plasm is supported by a number of analogies that we find to\nexist between cyanide compounds, especially cyanic acid (C N O H.) and\nthe living albumin. Both bodies are fluid and transparent at a low\ntemperature, while they set at a higher; both of them break up in the\npresence of water into carbonic acid and ammonia; both produce urea by\ndisassociation (by the intramolecular surrounding of the atoms, not by\ndirect oxydation). \"The similarity of the two substances is so great,\"\nsays Pfl\u00fcger, \"that I might describe cyanic acid as a semi-living\nmolecule.\" Both substances grow in the same way by concatenation of the\natoms, homogeneous groups of atoms joining together chainwise in large\nmasses.\n\nThere is an especial interest in connection with the theory of\narchigony and its physical basis in the chemical fact that cyanogen and\nits compounds--cyanide of potassium, cyanic acid, cyanide of hydrogen,\netc.--are only formed at incandescent heat; that is to say, when the\nrequisite inorganic nitrogenous compounds are put with glowing coals,\nor the mixture is heated to incandescence. Other essential constituents\nof albumin, such as carburetted hydrogen or alcohol-radical, can be\nformed synthetically in heat. \"Thus,\" says Pfl\u00fcger, \"nothing is clearer\nthan the possibility of the formation of cyanic compounds when the\nearth was entirely or partially in a state of incandescence or great\nheat. We see how extraordinarily all the facts of chemistry point to\nfire as the force that has produced the constituents of albumin by\nsynthesis. Hence life was born from fire, and the chief conditions of\nits appearance are associated with a time when the earth was a glowing\nball of fire. When we remember the incalculably long period in which\nthe surface of the earth was slowly cooling, we see that cyanogen, and\nthe compounds that contained cyanogen, and carburetted hydrogen, had\nplenty of time and opportunity to follow out to any extent their great\ntendency to the transposition and formation of polymeria (chains of\natoms), and, with the co-operation of oxygen and afterwards of water\nand salts, to evolve into the self-decomposable albumin which is living\nmatter.\" In regard to the latter feature, it is well to emphasize the\nfact that, as will be understood, there must have been a long series\nof chemical intermediary stages between the incandescent formation of\ncyanogen and the appearance of the aqueous living plasm.\n\nPfl\u00fcger's cyanogen theory does not conflict with my monera theory, but\nrather supplements it, by its careful and thoroughly scientific study\nof a much earlier stage of primitive biogenesis--in a sense, the first\nperiod of preparation for the formation of albumin. This must be well\nborne in mind in view of the attacks which have lately been made on\nit by Neumeister and other vitalists; it is supposed to be untenable,\nbecause \"there is an impassable gulf between cyanic compounds and\nproteids.\" This criticism is answered by the living albumin itself,\nwhich always contains in its nitrogenous decomposition products the\nradical of cyanide or other substances (urea) that can be artificially\nproduced from cyanic compounds. Another objection is that \"the cyanic\ncompounds which were formed in the heat must have very quickly perished\non the subsequent appearance of water.\" The objection has no weight,\nsince we can form no definite idea as to the special conditions of\nchemical activity in those times. We can only say that the conditions\nduring this long period (embracing millions of years) were totally\ndifferent from those of chemical action at the surface of the earth\nto-day. The real ground of the opposition of Neumeister and other\nvitalists is their dualistic conception of nature, which will maintain\nat all costs the deep gulf between the organic and inorganic worlds.\n\nMax Verworn, in his _General Physiology_, has fully described and\ncriticised the various theories of the appearance of life on the earth.\nHe rightly attributes a great value to Pfl\u00fcger's cyanogen theory,\nbecause \"it makes a strictly scientific study of the problem in close\nrelation to the facts of physiological chemistry, and goes thoroughly\ninto detail.\" He agrees with Pfl\u00fcger when he expresses himself as\nfollows: \"I would say, therefore, that the first albumin to be formed\nwas in point of fact living matter, endued with the property in all its\nradicals of attracting especially homogeneous parts with great force\nand preference, in order to build them chemically into the molecule,\nand so grow indefinitely. On this view the living albumin need not\nhave a constant molecular weight, because it is a huge molecule in an\nunceasing process of formation and decomposition, probably acting on\nthe ordinary chemical molecules as a sun does on a small meteor.\" This\ntheory, which I believe to be correct, is also maintained by many other\nmodern scientists who have made a particular study of the difficult\nquestion of the nature and origin of the albuminoids.\n\nNow that we have described the various modern theories of archigony\nthat are worth considering, and recognized with N\u00e4geli that the\noriginal development of the organic from the inorganic is a fact, we\nmay glance at the older theories which, under the name of \"spontaneous\ngeneration,\" afforded matter for a good deal of controversy. It is true\nthat they are now almost entirely abandoned, but the experiments in\nconnection with them excited a good deal of interest and led to many\nmisunderstandings.\n\nThe older hypotheses of \"spontaneous generation\" do not bear on our\nproblem of archigony (or the first development of living matter from\nlifeless inorganic carbon compounds) but relate to the formation of\nlower organisms out of the putrid and decomposing organic elements of\nhigher organisms. In order to distinguish these hypotheses from the\ntotally different theory of archigony, it is better to give them the\nname of saprobiosis (an earlier name was necrobiosis), which means\nthe birth of living from dead (_nekron_) or putrid (_sapron_) organic\nmatter. Saprobiosis is preferable, because necrobiosis is better used\nin a different sense, for the dead organic parts which gradually bring\nabout the death of the living body (see p. 106). It was believed in\nancient times that lower organisms could arise from the dead remains of\nhigher organisms, such as fleas from manure, lice from morbid pustules\nin the skin, moths from old furs, and mussels from slime in the water.\nAs these stories were supported by the authority of Aristotle, and\non that account believed by St. Augustine and other fathers, and\nreconciled with the faith, they were held until the beginning of the\neighteenth century. Even in the year 1713 the botanist Heucherus stated\nthat the green duck-weed (_lemna_) is only condensed grease from the\nsurface of foul standing water, and that water-cress was formed from it\nin fresh running water.\n\nThe first scientific refutation of these old stories was made by the\nItalian physician, Francisco Redi, in 1674, on the basis of very\ncareful experiment: he was persecuted for \"unbelief\" on that account.\nHe showed that all these animals arose from eggs that had been\ndeposited by female animals in dung, skin, fur, slime, etc. But at that\ntime the proof could not be extended to the tape-worms, maw-worms,\nand other intestinal animals (_entozoa_), which live inside other\nanimals (in the bowels, blood, brain, or liver). It was still believed\nthat these arise from diseased parts of the host-animals in which\nthey live, until about the middle of the nineteenth century. It was\nnot until 1840-1860 that it was shown by the experiments of Siebold,\nLeuckart, Van Beneden, Virchow, and other famous biologists, that all\nthese intestinal animals have come from without into the animals they\nlive in, and propagate there by eggs. Of late years the proof has been\napplied all round.\n\nOn the other hand, the hypothesis of saprobiosis retained its position\nuntil quite recently for one section of the smallest and lowest\norganisms, the microscopic forms of life, invisible to the naked eye,\nwhich were formerly called infusoria, and which we now call by the\nwider name of protists or unicellulars. When Leeuwenhoek discovered the\ninfusoria in 1675 with the newly invented microscope, and showed that\nthey arise in great quantities in infusions of hay, moss, flesh, and\nother putrid organic substances, it was generally believed that they\nwere spontaneously generated there. The Abb\u00e9 Spallanzani showed in 1687\nthat no infusoria appear in these infusions if they are well boiled and\nthe vessel is carefully closed; the boiling kills the germs in them,\nand the exclusion of air prevents the entrance of fresh germs. In spite\nof this, many microscopists still believed that certain infusoria,\nparticularly the very small and simple bacteria, could be born directly\nfrom putrid or diseased tissues of organisms, or from decomposing\norganic fluids; the opinion was maintained by Pouchet at Paris in 1858,\nand afterwards by Charlton Bastian. The controversy about the subject\nmoved the Paris Academy in 1858 to offer a prize for \"careful research\nthat would throw new light on the question of spontaneous generation.\"\nIt fell to the famous Louis Pasteur, who proved, by a series of\ningenious experiments, that there are everywhere in the atmosphere\nnumbers of germs of microbes or microscopic organisms floating among\nthe dust particles, and that these grow and reproduce when they reach\nwater. Not only infusoria, but also small highly organized plants and\nanimals--such as lichens, mosses, rotifers, and tardigrades--can live\nfor months in a desiccated condition, be carried in all directions\nby the wind, and reawaken into life when they reach water. On the\nother hand, Pasteur showed convincingly that organisms never appear\nin infusions of organic substances when they are sufficiently boiled\nand the atmosphere that reaches them has been chemically purified. He\nsummed up the results of his rigorous experiments, which were confirmed\nby Robert Koch and other bacteriologists, and gave rise to the modern\nprecautions as to disinfection, in the maxim: \"Spontaneous or equivocal\ngeneration is a myth.\"\n\nThe famous experiments of Pasteur and his successors had destroyed the\nmyth of saprobiosis, but not the theory of archigony. These entirely\ndifferent hypotheses are still very frequently confused, because the\nold title of \"spontaneous generation\" is used for both. We still read\nsometimes that the \"unscientific\" belief in abiogenesis has been\ndefinitely refuted by these experiments, and that the question of\nthe origin of life has thus become an insoluble enigma. There is an\nastonishing superficiality and lack of discernment in such remarks;\nthey would hardly be possible in any other branch of science. But in\nbiology--many of its distinguished representatives continue to say--we\nhave only to observe and correctly describe facts; the formation\nof clear ideas and the indulgence in reflection on the facts are\nunnecessary and dangerous, and, therefore, to be avoided! It is due\nto this pitiable condition of biological methods of research that\nour hypothesis of archigony is still attacked, or else ignored. Why?\nBecause the false hypothesis of saprobiosis, which has absolutely\nnothing in common with it but the name \"spontaneous generation,\" has\nbeen refuted by the experiments of Pasteur and his colleagues![9]\nThese experiments prove nothing whatever beyond the fact that new\norganisms are not formed in certain infusions of organic matter--under\ndefinite, artificial conditions. They do not even touch the important\nand pressing question, which alone interests us: \"How did the earliest\norganic inhabitants of our earth, the primitive organisms, arise from\ninorganic compounds?\"\n\nThe great popularity of the famous experiments of Pasteur on\nspontaneous generation, and the unfortunate confusion of ideas which\nwas caused by the false interpretation of his results, make it\nnecessary for me to say a word on the general value of scientific\nexperiments in many questions. Since Bacon introduced experiment into\nscience three hundred years ago, and gave it a logical basis, both\nour speculative knowledge of nature and the practical application\nof our knowledge made remarkable progress. New methods of research\nmade it possible for modern workers to penetrate far more deeply into\nthe nature of phenomena than the older thinkers had done, who had no\nknowledge of experiment. Especially in the nineteenth century the\ndevelopment of the experimental method, or the putting of a question to\nnature, led to enormous advances in the various sciences.\n\nIn the subject we are considering the question to be put to nature\nis: \"Under what conditions and in what manner is living matter (or\nplasm) formed from lifeless inorganic compounds?\" We may confidently\nassume that in the period when archigony took place--the time when\norganic life first appeared on the cooled surface of the earth, at\nthe beginning of the Laurentian Age--the conditions of existence were\ntotally different from what they are now; but we are very far from\nhaving a clear idea of what they were, or from being able to reproduce\nthem artificially. We are just as far from having a thorough chemical\nacquaintance with the albuminous compounds to which plasm belongs.\nWe can only assume that the plasma-molecule is extremely large, and\nmade up of more than a thousand atoms, and that the arrangement and\nconnection of the atoms in the molecule are very complicated and\nunstable. But of the real features of this intricate structure we\nhave as yet no conception. As long as we are ignorant of this complex\nmolecular structure of albumin, it is useless to attempt to produce\nit artificially. Yet in this position of the matter we would seek\nto produce that great wonder of life, the plasm, artificially, and\nwhen the experiment miscarries (as we should expect) we cry out:\n\"Spontaneous generation is impossible.\"\n\nWhen we carefully consider the intelligent experiments that have been\nmade in regard to archigony in the light of these facts, it is clear\nthat their negative result does not in the slightest degree affect our\nquestion. The much-admired experiments of Pasteur and his colleagues\nprove merely that in certain artificial conditions infusoria are not\nformed in decomposing organic compounds (or the dead tissues of highly\norganized histona); they cannot possibly prove that saprobioses of this\nkind do not take place under other conditions. They tell us nothing\nwhatever about the possibility or reality of archigony; in the form\nin which I put the scientific hypothesis in 1866 it is completely\nuntouched by all these experiments. It remains intact as the first\nattempt to give a provisional reply--if only in the form of a temporary\nhypothesis--on the basis of modern science to one of the chief\nquestions of natural philosophy.\n\nIn my _General Morphology_ (1866), and afterwards in my _Biological\nStudies on the Monera and other Protists_, and the first volume of\nmy _Systematic Phylogeny_ (1894), I attempted to sketch in detail\nthe stages of the process to which I give the name of archigony. I\ndistinguished two principal stages--_autogony_ (the formation of the\nfirst living matter from inorganic nitrogenous carbon-compounds) and\n_plasmogony_ (the formation of the first individualized plasm; the\nearliest organic individuals in the form of monera). In more recent\nefforts I have made use of the important results reached by N\u00e4geli\n(1884) in his investigations of the same subject. In regard to some\nimportant points relating to the chemico-physical part of the question,\nN\u00e4geli has, in his _Mechanico-physiological Theory of Evolution_\n(chapter ii.), gone more into the details of the process of archigony.\nTo the earliest living things, which were formed by \"unicellular\norganization\" of the plasm out of simple inorganic compounds, he\ngives the name of _probia_ or _probionta_, and thinks that these had\nan even simpler structure than my monera. This view seems to rest on\na misunderstanding. N\u00e4geli does not strictly follow my definition,\n\"organisms without organs\" (that is to say, structureless living\nparticles of plasm without morphological differentiation), but he has\nin mind the individual rhizopod-like organisms which I had at first\ndescribed as monera--_protam\u0153ba_, _protogenes_, _protomyxa_, etc. In\nmy present view the chromacea, or plasmodomous phytomonera, are much\nmore important than these plasmophagous zoomonera. It is curious that\nN\u00e4geli does not make thorough use of their primitive organization for\nthe establishment of his theory, although he has had the great merit of\ndescribing these most primitive of all living organisms as unicellular\nalg\u00e6 (1842). As a matter of fact, the simplest chromacea (chroococcus\nand related forms) approach so closely to his hypothetical probia\nor probionta that the only things we can regard as the rudiments of\norganization in the chroococcacea are the secretion of a protective\nmembrane about the homogeneous plasma-globule and the separation of\nthe blueish-green cortical zone from the colorless central granule.\nThe more important of the further conclusions of N\u00e4geli are those\nwhich relate to the mode of the primitive abiogenesis and the frequent\nrepetition of this physical process.\n\nRecently Max Kassowitz, in the second volume of his _General Biology_\n(1899), has gone fully into the various stages of the process of\narchigony, as a sequel to his metabolic theory of the building up and\ndecay of plasm, from the point of view of physiological chemistry. He\nsays very truly that the development of living from lifeless matter\nmust not be conceived as a sudden leap; the very complicated chemical\nunities which now form the basis of life have been slowly and gradually\nevolved during an incalculably long period by the way of substitution\nfor simpler compounds. We may join these views--which generally accord\nwith my earlier deductions--with Pfl\u00fcger's cyanogen theory, and so draw\nup the following theses:\n\n1. A preliminary stage to archigony is the formation of certain\nnitrogenous carbon-compounds which may be classed in the cyanic\ngroup (cyanic acid, etc.). 2. When the crust of the earth stiffened,\nwater was formed in the fluid condition; under its influence, and in\nconsequence of the great changes in the carbonic-acid laden atmosphere,\na series of complicated nitrogenous carbon-compounds were formed from\nthese simple cyanic compounds, and these first produced albumin (or\nprotein). 3. The molecules of albumin arranged themselves in a certain\nway, according to their unstable chemical attractions, in larger groups\nof molecules (pleona or micella). 4. The albumin-micella combined to\nform larger aggregations, and produced homogeneous plasma-granules\n(plassonella). 5. As they grew the plassonella divided, and\nformed larger plasma-granules of a homogeneous character: monera\n(= probionta). 6. In consequence of surface-strain or of chemical\ndifferentiation, there took place a separation of the firmer cortical\nlayer (membrane) from the softer marrow layer (central granule), as in\nmany of the chromacea. 7. Afterwards the simplest (nucleated) cells\nwere formed from these unnucleated cytodes, the hereditary mass of the\nplasm gathering within the monera and condensing into a firm nucleus.\n\nIt is an interesting, but at present unanswered, question whether the\nprocess of archigony only occurred once in the course of time or was\nfrequently repeated. Reasons can be given for both views. Pfl\u00fcger\nsays: \"In the plant the living albumin only continues to do what it\nhas done ever since its origin--constantly to regenerate itself or to\ngrow; hence I believe that all the albumin in the world comes from that\nsource. On that account I doubt if spontaneous generation takes place\nin our time. Moreover, comparative biology directly shows that all life\nhas come from one single root.\" However, this view does not exclude the\npossibility of the chemical process of spontaneous plasmodomism having\nbeen frequently repeated--under like conditions--in the same form in\nprimordial times.\n\nOn the other side, N\u00e4geli especially has pointed out that there is\nno reason to prevent us from thinking that archigony was repeated\nseveral times, even down to our own day. Whenever the physical\nconditions for the chemical process of plasmodomism were given, it\nmight be repeated anywhere at any time. As to locality, the sea-shore\nprobably affords the most favorable conditions; as, for instance, on\nthe surface of fine moist sand the molecular forces of matter in all\nits conditions--gaseous, fluid, viscous, and solid--find the best\nconditions for acting on each other. It is a fact that to-day all the\nvarious evolutionary forms of living matter--from the simplest moneron\n(chroococcus) to the plain nucleated cell, from this to the highly\norganized cell of the radiolaria and infusoria, from the simple ovum to\nthe most elaborate tissue-structure in the higher plants and animals,\nfrom the amphioxus to man--come in an order of succession. There are\nonly two ways of explaining this fact: either the simplest living\norganisms, the chromacea and bacteria, the palmella and am\u0153b\u00e6, have\nremained unchanged or made very little advance in organization since\nthe beginning of life--more than a hundred million years; or else\nthe phylogenetic process of their transformation has been frequently\nrepeated in the course of this period, and is being repeated to-day.\nEven if the latter were the case, we should hardly be in a position to\nlearn it by direct observation.\n\nAssuming that the simplest organisms are still formed by abiogenesis,\nthe direct observation of the process would probably be impossible,\nor at least extremely difficult, for the following reasons: 1. The\nearliest and simplest organisms are most probably globular particles\nof plasm, without any visible structure, like the simplest living\nchromacea (_chroococcus_). 2. These plasmodomous monera cannot be\ndistinguished from the chromoplasts (chlorophyll-granules), which live\ninside plant-cells, and may continue after the death of the cells\nto multiply independently by cleavage. 3. We must admit with N\u00e4geli\nthat the original size of these probionta (in spite of the relatively\ncolossal size of their molecules) is very small--much too small to\ncome within the range of the best microscope. 4. In the same way the\nprimitive metabolism and the slow, simple growth of these monera would\nnot come within direct observation. 5. As a matter of fact, we do often\nfind in stagnant water, and in the sea, tiny granules which consist, or\nseem to consist, of plasm. We usually regard them as detached portions\nof dead animals or plants; little isolated chlorophyll-granules that\nmay be found everywhere are looked upon as rejected products of vegetal\ncells. But who could refute the assumption that they are really\nplassonella or young monera, which grow slowly and unite with similar\nparticles to form larger plasmic bodies?\n\nIt is often objected to our naturalistic and monistic conception of\narchigony that we have not yet succeeded in forming albuminous bodies,\nand especially plasm, in our chemical laboratories by artificial\nsynthesis; from this the perverse dualistic conclusion is drawn that\nit is only supernatural vital forces that can do this. It is forgotten\nthat we do not yet know the complicated structure of albuminous\nbodies, and that we do not yet know what really happens inside the\ngreen chlorophyll-granules which in every plant-cell convert the\nradiant energy of sunlight into the virtual energy of the new-formed\nplasm. How can we be expected to reproduce synthetically, with the\nimperfect and crude methods of present chemistry, an elaborate chemical\nprocess the nature of which is not analytically known to us? However,\nthe worthlessness of this sceptical objection is obvious: we can\nnever claim that a natural process is supernatural because we cannot\nartificially reproduce it.\n\n\n\n\nXVI\n\nTHE EVOLUTION OF LIFE\n\n Inorganic and organic evolution--Biogenesis and\n cosmogenesis--Mechanical evolution--Mechanics of phylogenesis--Theory\n of selection--Theory of idioplasm--Phyletic vital force--Theory of\n germ-plasm--Progressive heredity--Comparative morphology--Germ-plasm\n and hereditary matter--Theory of mutation--Zoological and botanical\n transformism--Neo-Lamarckism and Neo-Darwinism--Mechanics of\n ontogenesis--Biogenetic law--Tectogenetic ontogeny--Experimental\n evolution--Monism and biogeny.\n\n\nI fully explained in my _General Morphology_ (1866) the profound\nimportance of the science of evolution in relation to our monistic\nphilosophy. A popular synopsis of this is given in my _History of\nCreation_, and is briefly repeated in the thirteenth chapter of the\n_Riddle_. I must refer the reader to these works, especially the\nlatter, and confine myself here to a consideration of some of the\nprincipal general questions of evolution in the light of modern\nscience. The first thing to do is to compare the conflicting views on\nthe nature and significance of biogenesis which still face each other\nat the beginning of the twentieth century.\n\nThe essential unity of inorganic and organic nature, which I endeavored\nto establish in the second book of the _General Morphology_, and the\nsignificance of which I explained in the fourteenth chapter of the\n_Riddle_, is found through the whole course of its development, in\nthe causes of phenomena and their laws. Hence, in dealing with the\nevolution of organisms, we reject vitalism and dualism, and maintain\nour conviction that it can always be traced to physical forces (and\nespecially chemical energy). As we regard plasm as the basis of it\n(chapter vi.), we may say that organic evolution depends on the\nmechanics and chemistry of the plasm. We postulate no supernatural\nvital force for the explanation of physiological functions, and we are\njust as far from admitting it as regulator or agency of the biogenetic\nprocess.\n\nIf we understand by biogeny the sum total of the organic evolutionary\nprocesses on our planet, by geogeny the processes at work in the\nformation of the earth itself, and by cosmogony those that produced the\nwhole world, biogeny is clearly only a small part of geogeny, and this\nin turn only a small section of the vast science of cosmogony. This\nimportant relation is evident enough, yet often overlooked; it holds\nboth of time and space. Even if we suppose that the biogenetic process\noccupied more than a hundred million years, this period is probably\nmuch shorter than that which our planet has needed for its development\nas a cosmic body--from the first detachment of the nebular ring from\nthe shrinking body of the sun to its condensation into a rotating\nsphere of gas, and from this to the formation of the incandescent\nglobe, the stiffening of the crust at its surface, and finally the\ndownpour of fluid water. It was not until this last stage that carbon\ncould begin its organogenetic activity and proceed to the formation of\nplasm. But even this long geogenetic process is, as regards space and\ntime, only a very small part of the illimitable history of the world.\nIf we further assume that organic life develops on other cosmic bodies\n(_Riddle_, chapter xx.) in the same way as on our earth under like\nconditions, the whole sum of all these biogenetic processes is only a\nsmall part of the all-embracing cosmogenetic process. The vitalistic\nbelief that its mechanical course was interrupted from time to time\nby the supernatural creation of organisms is opposed to pure reason,\nthe unity of nature, and the law of substance. We must, therefore, hold\nfast above all to the conviction that all biogenetic processes are\njust as reducible to the mechanics of substance as all other natural\nphenomena.\n\nThe mechanical and natural character of the development of inorganic\nnature, the earth and the whole material world, was established\nmathematically at the end of the eighteenth century by the great\natheist Laplace in his _M\u00e9canique C\u00e9leste_ (1799). The similar\ncosmogony which Kant had expounded in 1755 in his _General Natural\nHistory and Theory of the Heavens_ only obtained recognition at a\nlater date (_Riddle_, chapter xiii.). But the possibility of giving\na mechanical explanation of organic nature was not seen until Darwin\nprovided a solid foundation for the theory of descent by his theory of\nselection in 1859. I made the first comprehensive attempt to do this in\n1866 in my _General Morphology_, the aim of which is expressed in the\ntitle: \"General outlines of the science of organic forms, mechanically\ngrounded on Darwin's improvement of the theory of descent.\" Especially\nin the second volume of the work, the \"General Evolution of Organisms,\"\nI endeavored to show that both sections of the science, ontogeny (or\nembryology) and phylogeny, can be reduced to physiological activities\nof the plasm, and so explained mechanically, in the wider meaning of\nthe word.\n\nWhen I stated the nature and the aim of phylogeny in 1866, most\nbiologists regarded my attempt as unjustifiable, as they did Darwinism\nitself, of which it was a natural consequence. Even the famous \u00c9mil\nDubois-Reymond, to whom as a physiologist it should have been welcome,\ndescribed it as \"a poor romance\"; he compared my first attempts\nto construct the genealogical tree of the organic classes, on the\nevidence of paleontology, comparative anatomy, and ontogeny, to the\nhypothetical labors of philologists to draw up the genealogical tree\nof the legendary Homeric heroes. As a matter of fact, I had myself\ndescribed my imperfect effort as merely a provisional sketch, as a\ntemporary hypothesis that would open the way for later and better\nresearch. A single glance at the immense literature of phylogeny\nto-day shows how much has been done since in this province, and how\nfar we have advanced in the establishment of the features of evolution\nby means of the united labors of numbers of able paleontologists,\nanatomists, and embryologists. Ten years ago I attempted, in the three\nvolumes of my _Systematic Phylogeny_, to give a comprehensive statement\nof the results attained. My chief aim was, on the one hand, to\nconstruct a natural system of organisms on the basis of their ancestral\nhistory, and on the other hand to prove the mechanical character of\nthe phylogenetic process. All the activities of organisms which are at\nwork in the transformation of species and the production of new ones\nin the struggle for existence may be reduced to their physiological\nfunctions--to growth, nutrition, adaptation, and heredity; and these\nagain to the mechanics and chemistry of the plasm. The struggle for\nlife is itself a mechanical process, in which natural selection uses\nthe disproportion between the excess of germs and the restricted\nmeans of existence, in conjunction with the variability of species,\nin order to produce new purposive structures mechanically and without\nany preconceived design. This teleological mechanicism has no need of\na mysterious design or finality; it takes its place in the general\norder of mechanical causality which controls all the processes in the\nuniverse. Natural finality is only a special instance of mechanical\ncausality. The one is subordinate to the other, not opposed to it, as\nKant would have it.\n\nThe effort that the great Lamarck made in 1809, in his _Philosophie\nZoologique_, to establish transformism deserves high appreciation from\nmonists, because it was the first attempt to give a natural explanation\nof the origin of the countless species of organic forms which inhabit\nour planet. Up to that time it had been the fashion to attribute their\norigin to a miraculous intervention of the Creator. This metaphysical\ncreationism had now to face physical evolutionism. Lamarck explained\nthe gradual formation of organic species by the interaction of\ntwo physiological functions--adaptation and heredity. Adaptation\nconsists in the improvement of organs by use, and degeneration by\ndisuse; heredity acts by transmitting the features thus acquired to\nposterity. New species arise by physiological transformation from\nolder species. The fact that this great thought was overlooked for\nhalf a century does not detract from its profound significance. But it\nonly obtained general recognition when Darwin had supplemented it and\nfilled up its causal gaps by the theory of selection in 1859. Apart\nfrom this specifically Darwinian feature (whether it be true or not),\nthe fundamental idea of transformism is now generally received; it\nis admitted to-day even by metaphysicians who maintained a spirited\nopposition to it thirty years ago. The fact of the progressive\nmodification of species is only intelligible on Lamarck's theory\nthat the actual species are the transformed descendants of older\nspecies. In spite of all the learning and zeal with which the theory\nhas been attacked, it has proved irrefutable; nor can any one suggest\na better theory to replace it. This may be said particularly of its\nchief consequence--the descent of man from a series of other mammals\n(proximately from the apes).\n\nThe high value of Darwin's theory of selection for the monistic biology\nis now acknowledged by all competent and impartial authorities\non the science. In the course of the forty-four years since it\nfound its way into every branch of biology, it has been employed\nin more than a hundred large works and several thousand essays in\nexplaining biological phenomena. This alone is enough to show its\nprofound importance. Hence it is mere ignorance of the subject and\nits literature to say, as has been done several times of late, that\nDarwinism is in decay, or even \"dead and buried.\" However, absurd\nwritings of this kind (such as Dennert's _At the Death-bed of\nDarwinism_) have a certain practical influence, because they fall\nin with the prevailing superstition in theology and metaphysics.\nUnfortunately, they also seem to obtain notice from the circumstance\nthat a few botanists persistently attack the Darwinian theory. One of\nthe most conspicuous of these is Hans Driesch, who affirms that all\nDarwinists (and therefore the great majority of modern biologists) have\nsoftening of the brain, and that Darwinism is (like Hegel's philosophy)\nthe delusion of a generation. The arrogance of this conceited writer is\nabout equal to the obscurity of his biological opinions, the confusion\nof which is covered by a series of most extravagant metaphysical\nspeculations. All these attacks have lately been met very ably by\nPlate in his work, _On the Significance of the Darwinian Principle\nof Selection and the Problem of the Foundation of Species_ (second\nedition, 1903). The most thorough of recent defences of Darwinism\nis that made by August Weismann in his _Lectures on the Theory of\nDescent_ (1902) and other works. But the distinguished zoologist\ngoes too far when he seeks to prove the omnipotence of selection and\nwishes to ground it on an untenable molecular hypothesis--the theory\nof germ-plasm, which we will consider presently. Apart from these or\nother exaggerations, we may say with Weismann that Lamarck's theory of\ndescent received a sound causal basis by Darwin's theory of selection.\nIts real foundations are these three phenomena: heredity, adaptation,\nand the struggle for existence. All three are, as I have often said,\nof a purely mechanical and not a teleological nature. Heredity is\nclosely bound up with the physiological function of reproduction, and\nadaptation with nutrition; the struggle for life follows logically and\nmathematically from the disproportion between the number of potential\nindividuals (germs) and of actual individuals that grow to maturity and\npropagate the species.\n\nWhen I had, in my _General Morphology_, endeavored to gain acceptance\nfor Darwin's theory of selection, and had presented evolution as a\ncomprehensive theory from the point of view of the monistic philosophy,\na number of works, sometimes of value, appeared, which made special\nstudies of the various parts of the immense province. Eighteen years\nafterwards a greater work was published, which started from the same\nmonistic principles, but reached the same conclusion by a different\nway. In 1884 Carl N\u00e4geli, one of our ablest and most philosophic\nbotanists, issued his _Mechanical-physiological Theory of Evolution_.\nThis interesting book consists of various parts. It is especially\nnotable that evolution is presented in it as the one possible\nand natural theory of the origin of species; even morphology and\nclassification are treated explicitly as \"phylogenetic sciences.\" The\nchapter on archigony--a dark and dangerous problem that is generally\navoided by scientists!--is one of the best that has been written on the\nsubject. On the other hand, N\u00e4geli rejects Darwin's theory of selection\naltogether, and would explain the origin of species by an inner\n\"definitely directed variation,\" independently of the conditions of\nexistence in the outer world. As Weismann has properly observed, this\ninternal principle of evolution, which dispenses with adaptation in\nthe true sense of the word, is at the bottom merely a \"phyletic vital\nforce.\" It is not made more acceptable by N\u00e4geli when he builds up a\nsubtle metaphysical system on it and postulates a special \"principle\nof isagitation.\" But the idioplasm theory he connects with it is of\nsome value, since it goes more fully into the differentiation of the\ncell-plasm into two physiologically different parts--the idioplasm of\nthe hereditary matter and the trophoplasm as nutritive matter of the\ncell.\n\nThe vitalist and teleological idea of an internal principle of\nevolution, that determines the origin of animal and plant species\nindependently of the environment and its conditions, is not only\nfound in the \"mechanical-physiological\" theory of N\u00e4geli, but also in\nseveral other attempts to explain the agencies of the transformation of\nspecies. All these efforts are welcomed by the academic philosophers\nwith their Kantist dualism (mechanicism on the right, teleology on\nthe left), and who are particularly anxious to save the supernatural\nelement, Reinke's \"cosmic intelligence,\" or the wisdom of the Creator,\nor the divine creative thought. All these dualistic and teleological\nefforts have the same fault: they overlook, or fail to appreciate\nproperly, the immense influence of the environment on the shaping\nand modification of organisms. When, moreover, they deny progressive\nheredity and its connection with functional adaptation, they lose the\nchief factor in transformation. This applies also to the theory of\ngerm-plasm.\n\nThe desire to penetrate deeper into the mysterious processes that\ntake place in the plasm in the physiological activities of heredity\nand adaptation has led to the formulation of a number of molecular\ntheories. The chief of these are the pangenesis theory of Darwin\n(1878), my own perigenesis theory (1876), the idioplasm theory of\nN\u00e4geli (1884), the germ-plasm theory of Weismann (1885), the mutation\ntheory of De Bries, etc. As I have already dealt with these in the\nsixth chapter (as well as in the ninth chapter of the _History of\nCreation_), I may refer the reader thereto. None of these or similar\nattempts has completely solved the very difficult problems in question,\nand none of them has been generally received. There is, however, one\nof them that we must consider more closely, because it is not only\nregarded by many biologists as the greatest advance of the theory of\nselection since Darwin, but it also touches the roots of several of\nthe chief problems of biogeny. I mean the much-discussed germ-plasm\ntheory of August Weismann (of Freiburg), one of our most distinguished\nzoologists. He has not only promoted the theory of descent by his\nmany writings during the last thirty years, but has also put in its\nproper light the great importance and entire accuracy of the theory of\nselection. But, in his efforts to provide a molecular-physiological\nbasis for it, he has proceeded by way of metaphysical speculation to\nframe a quite untenable theory of the plasm. While fully recognizing\nthe ability and consistency and the able treatment which Weismann\nhas shown, I am compelled once more to dissent from him. His ideas\nhave recently been completely refuted by Max Kassowitz (1902) in his\n_General Biology_, and Ludwig Plate in the work I mentioned on the\nDarwinian principle of selection. We need not go into the details of\nthe complicated hypothesis as to the molecular structure of the plasm\nwhich Weismann has framed in support of his theory of heredity--his\ntheory of biophora, determinants, ideas, etc.--because they have no\ntheoretical basis and are of no practical use. But we must pass some\ncriticism on one of their chief consequences. In the interest of his\ncomplicated hypotheses, Weismann denies one of Lamarck's most important\nprinciples of transmutation--namely, the inheritance of acquired\ncharacters.\n\nWhen I made the first attempt in 1866 to formulate the phenomena of\nheredity and adaptation in definite laws and arrange these in series,\nI drew a distinction between conservative and progressive heredity\n(chapter ix., _History of Creation_). Conservative heredity, or the\ninheritance of inherited characters, transmits to posterity the\nmorphological and physiological features which each individual has\nreceived from his parents. Progressive heredity, or the inheritance of\nacquired characters, transmits to offspring a part of those features\nwhich were acquired by the parents in the course of their individual\nlives. The chief of these are the characters that are caused by the\nactivity of the organs themselves. Increase in the use of the organs\ncauses a greater access of nourishment and promotes their growth;\ndecrease in the exercise of organs has the contrary effect. We have\nexamples at hand in the modification of the muscles or the eyes, the\naction of the hand or throat in painting or singing, and so on. In\nthese and all the arts the rule is: Practice makes perfect. But this\napplies almost universally to the physiological activity of the plasm,\neven its highest and most astounding function--thought; the memory and\nreasoning capacity of the phronema are improved by constant exercise of\nthe cells which compose this organ, just as we find in the case of the\nhands and the senses.\n\nLamarck recognized the great morphological significance of this\nphysiological use of the organs, and did not doubt that the\nmodification caused was transmitted to offspring to a certain extent.\nWhen I dealt with this correlation of direct adaptation and progressive\nheredity in 1866, I laid special stress on the \"law of cumulative\nadaptation\" (_General Morphology_, ii., p. 208). \"All organisms undergo\nimportant and permanent (chemical, morphological, and physiological)\nchanges when acted on by a change in its life-conditions, slight in\nitself, but continuing for a long time or being frequently repeated.\"\nAt the same time I pointed out that in this case two groups of\nphenomena are closely connected which are often separated--namely,\ncumulative heredity: firstly _external_, by the action of the external\nconditions (food, climate, environment, etc.), and secondly _internal_,\nby the reaction of the organism, the influence of internal conditions\n(habit, use and disuse of organs, etc.). The action of outer influences\n(light, heat, electricity, pressure, etc.) not only causes a reaction\nof the organism affected (energy of movement, sensation, chemosis,\netc.), but it has an especial effect as a trophic stimulus on its\nnutrition and growth. The latter element has been particularly studied\nby Wilhelm Roux; his functional adaptation (1881) coincides with my\ncumulative adaptation, the close relation of which to correlative\nadaptation I had pointed out in 1866. Plate has recently given this\n\"definitely directed variation\" the name of ectogenetic orthogenesis,\nor, briefly, ectogenesis.\n\nThe controversy about progressive heredity still continues here and\nthere. Weismann completely denies it, because he cannot bring it into\nharmony with his germ-plasm theory, and because he thinks there are\nno experimental proofs in support of it. A number of able biologists\nagree with him, led away by his brilliant argumentation. However,\nmany of them foolishly lay great stress on experiments in heredity\nwhich prove nothing; for instance, the fact that the offspring of a\nmammal that has had its tail cut off do not inherit the feature. A\nnumber of recent observations seem to prove that in a few cases even\ndefects of this sort (when they have caused profound and lasting\ndisease of the part affected) may be transmitted to offspring.\nHowever, as far as the formation of new species is concerned, the\nfact is of no consequence; in this it is a question of cumulative or\nfunctional adaptation. Experimental proofs of this are difficult to\nfind, if one wants a strict demonstration of the type of physical\nexperiments; the biological conditions are generally too complicated\nand offer too many weak points to rigorous criticism. The beautiful\nexperiments of Standfuss and C. Fisher (Zurich) have shown that changes\nin the environment (such as temperature or food) can cause striking\nmodifications that are transmitted to offspring. In any case, there are\nplenty of luminous proofs of progressive heredity in the vast arsenal\nof morphology, comparative anatomy, and ontogeny.\n\nComparative anatomy affords a number of most valuable arguments for\nother phylogenetic questions as well as progressive heredity; and the\nsame may be said of comparative anatomy and comparative ontogeny. I\nhave collected and illustrated a good many of these proofs in the new\nedition of my _Anthropogeny_. However, in order to understand and\nappreciate them aright, the reader must have some acquaintance with\nthe methods of critical comparison. This means not only an extensive\nknowledge of anatomy, ontogeny, and classification, but also practice\nin morphological thinking and reasoning. Many of our modern biologists\nlack these qualifications, especially those \"exact\" observers who\nerroneously imagine they can understand vast groups of phenomena by\naccurate description of detailed microscopic structures, etc. Many\ndistinguished cytologists, histologists, and embryologists have\ncompletely lost the larger view of their work by absorption in these\ndetails. They even reject some of the fundamental ideas of comparative\nanatomy, such as the distinction between homology and analogy;\nWilhelm His, for instance, declared that these \"academic ideas\" are\n\"unreliable tools.\" On the other hand, physiological experiments ought\nto contribute to the solution of morphological problems, and of these\nthey can say nothing. To show the incalculable value of comparative\nanatomy for phylogeny, I need only point to one of its most successful\ndepartments, the skeleton of the vertebrates, the comparison of the\nvarious forms of the skull, the vertebral column, the limbs, etc. It\nis not in vain that for more than a hundred years gifted scientists,\nfrom Goethe and Cuvier to Huxley and Gegenbaur, have devoted years\nof laborious research to the methodical comparison of these similar\nyet dissimilar forms. They have been rewarded by the discovery of the\ncommon laws of structure, which can only be explained in the sense of\nmodern evolution by descent from common ancestors.\n\nWe have a striking example of this in the limbs of mammals, which, with\nthe same internal skeletal structure, show a very great variety in\nouter form--the slender bones of the running carnivora and ungulates,\nthe oar-bones of the whale and seal, the shovel-bones of the mole and\nhypud\u00e6us, the wings of the bat, the climbing bones of the ape, and the\ndifferentiated limbs of the human body. All these different skeletal\nforms have descended from the same common stem-form of the oldest\nTriassic mammals; their various forms and structures are adapted in\nscores of ways to different functions; but they rise _through_ these\nfunctions, and all these functional adaptations can only be understood\nby progressive heredity. The theory of germ-plasm gives no causal\nexplanation whatever of them.\n\nThe majority of recent biologists are of opinion that of the two chief\nconstituents of the nucleated cell the cytoplasm of the cell-body\ndischarges the function of nutrition and adaptation, while the\ncaryoplasm of the nucleus accomplishes reproduction and heredity.\nI first advanced this view in the ninth chapter of the _General\nMorphology_ (in 1866); and it was afterwards solidly and empirically\nestablished by the excellent investigations of Eduard Strasburger, the\nbrothers Oscar and Richard Hertwig, and others. The elaborate finer\nstructures which these observers discovered in cell-division led to\nthe theory that the colorable part of the nucleus, chromatin, is the\nreal hereditary matter, or the material substratum of the energy of\nheredity. Weismann added the theory that this germ-plasm lives quite\nseparately from the other substances in the cell, and that the latter\n(the soma-plasm) cannot transmit to the germ-plasm the characters it\nhas acquired by adaptation. It is on the strength of this theory that\nhe opposes progressive heredity. The representatives of the latter\n(including myself) do not accept this absolute separation of germ-plasm\nfrom body-plasm; we believe that even in the process of cell-division\nin the unicellular organism there is partial blending of the two kinds\nof plasm (caryolysis), and that in the multicellular organism of the\nhistona also the harmonious connection of all the cells by their\nplasma-fibres makes it possible enough for all the cells in the body to\nact on the germ-plasm of the germ-cells. Max Kassowitz has shown how we\ncan explain this influence by the molecular structure of the plasm.\n\nAt the beginning of the twentieth century a new biological theory\naroused a good deal of interest, and was welcomed by some as an\nexperimental refutation of Darwin's theory of selection and by others\nas a valuable supplement to it. The distinguished botanist Hugo de\nBries (of Amsterdam) gave an interesting lecture at the scientific\ncongress at Hamburg in 1901 on \"The Mutations and Mutation-periods\nin the Origin of Species.\" Supported by many years of experiments in\nselection and some ingenious speculations, he thinks he has discovered\na new method of the transformation of species, an abrupt modification\nof the specific form at a bound, and so discredited Darwin's theory of\ntheir gradual change through long periods of time. In a large work on\n_Experiments and Observations on the Origin of Species in the Plant\nKingdom_ (1903), De Bries has endeavored to demonstrate the truth of\nhis theory of mutation. The warm approval which it won from a number\nof eminent botanists, and especially vegetal physiologists, was not\nshared by zoologists. Of these Weismann, in his _Lectures on the\nTheory of Descent_ (1902, ii. p. 358), and Plate in his _Problems of\nSpecies-formation_ (1903, p. 174), have dealt fully with the theory\nof mutation, and, while appreciating the interesting observations\nand experiments of De Bries, have rejected the theory he has built\non them. As I share their opinion, I may refer the reader who is\ninterested in these difficult problems to their works, and will\nrestrict myself here to the following observations. The chief weakness\nof the theory of mutation of De Bries is on its logical side, in\nhis dogmatic distinction between species and variety, mutation and\nvariation. When he holds the constancy of species as a fundamental\n\"fact of observation,\" we can only say that this (relative) permanence\nof species is very different in the different classes. In many\nclasses (for instance, insects, birds, many orchids and graminea) we\nmay examine thousands of specimens of a species without finding any\nindividual differences; in other classes (such as sponges, corals, in\nthe genera _rubus_ and _hieracium_) the variability is so great that\nclassifiers hesitate to draw up fixed species. The marked difference\nbetween various forms of variability which De Bries alleges cannot\nbe carried through; the fluctuating variations (which he takes to be\nunimportant) cannot be sharply distinguished from the abrupt mutations\n(from which new species are supposed to result at a bound). De Bries's\nmutations (which I distinguished in the _General Morphology_ as\n\"monstrous changes\" from other kinds of variation) must not be confused\nwith the paleontological mutations of Waagen (1869) and Scott (1894)\nwhich have the same name. The sudden and striking changes of habit\nwhich De Bries observed only in one single species of _\u0153nothera_\nvery rarely occur, and cannot be regarded as common beginnings of\nthe formation of new species. It is a curious freak of chance that\nthis species bears the name _\u0153nothera Lamarckiana_; the views of\nthe great Lamarck on the powerful influence of functional adaptation\nhave not been refuted by De Bries. It must be carefully noted, in\nfact, that De Bries is firmly convinced of the truth of Lamarck's\ntheory of descent, like all competent modern biologists. This must be\nwell understood, because recent metaphysicians see in the supposed\nrefutation of Darwinism the death of the whole theory of transformism\nand evolution. When they appeal in this sense to its most virulent\nopponents, Dennert, Driesch, and Fleischmann, we may remind them that\nthe curious sermons of these minor sophists are no longer noticed by\nany competent and informed scientist.\n\nNot only in the brilliant speculations of De Bries and N\u00e4geli, but\nalso in many other botanical works that have lately attempted to\nadvance the theory of descent, we find a striking difference from\nthe prevailing views of zoologists in the treatment of a number of\ngeneral biological problems. This difference is, of course, not\ndue to a disproportion of ability in the two great and neighboring\ncamps of biology, but to the differences in the phenomena that we\nobserve in plant life on the one hand and animal life on the other.\nIt must be noted particularly that the organism of the higher animals\n(including our own) is much more elaborately differentiated in its\nvarious organs and much more exposed to our direct experience than\nthat of the higher plants. The chief properties and activities of our\nmuscles, skeleton, nerves, and sense-organs, are understood at once\nin comparative anatomy and physiology. The study of the corresponding\nphenomena in the bodies of the higher plants is much more difficult.\nThe features of the innumerable elementary organs in the cell-monarchy\nof the animal body are much more intricate, yet at the same time much\nmore intelligible, than those of the cell-republic of the higher\nplant-body. Thus the phylogeny of the plants encounters much greater\ndifficulties than that of the animals; the embryology of the former\nsays much less in detail than that of the latter. We can understand,\ntherefore, why the biogenetic law is not so generally recognized by\nbotanists as by zoologists. Paleontology, which provides such valuable\nfossil material for many groups of the animal kingdom that we can\nmore or less correctly draw up their ancestral tree on the strength\nof this, gives us very little for most groups of the plant kingdom.\nOn the other hand, the large and sharply demarcated plant-cell, with\nits various organella, is much more valuable in connection with many\nproblems than the tiny animal-cell. For many physiological purposes,\nin fact, the higher plant body is more accessible to exact physical\nand chemical research than the higher animal body. The antithesis is\nless in the kingdom of the protists, as the difference between animal\nand vegetal life is mostly confined to difference of metabolism, and\nfinally disappears altogether in the province of the unicellular forms\nof life. Hence, for a clear and impartial treatment of the great\nproblems of biology, and especially of phylogeny, it is imperative to\nhave a knowledge of both zoological and botanical investigation. The\ntwo great founders of the theory of descent--Lamarck and Darwin--were\nable to penetrate so deeply into the mysteries of organic life and its\ndevelopment because they had extensive attainments both in botany and\nzoology.\n\nOf the various tendencies that have recently made their appearance\namong zoologists and botanists in the discussion of the theory\nof descent, we frequently find Neo-Lamarckism and Neo-Darwinism\ndistinguished as opposing schools. This opposition has no meaning\nunless we understand by it the alternatives of transformism--with or\nwithout the theory of selection. The one principle that distinguishes\nDarwinism proper from the older Lamarckism is the struggle for\nexistence and the theory of selection based on it. It is quite wrong\nto make the test an acceptance or rejection of progressive heredity.\nDarwin was just as firmly convinced as Lamarck or myself of the great\nimportance of the inheritance of acquired characters, and particularly\nof the inheritance of functional adaptations; he merely ascribed to it\na more restricted sphere of influence than Lamarck. Weismann, however,\ndenies progressive heredity altogether, and wants to trace everything\nto \"the omnipotence of natural selection.\" If this view of Weismann\nand the theory of germ-plasm he has based on it are correct, he alone\nhas the honor of founding a totally new (and in his opinion very\nfruitful) form of transformism. But it is quite wrong to describe this\nWeismannism as Neo-Darwinism, as frequently happens in England. It is\njust as wrong to call N\u00e4geli, De Bries, and other modern biologists who\nreject selection Neo-Lamarckists.\n\nIf the theory of descent is right, as all competent biologists now\nadmit, it puts on morphology the task of assigning approximately the\norigin of each living form. It must endeavor to explain the actual\norganization of each by its past, and to recognize the causes of its\nmodification in the series of its ancestors. I made the first attempt\nto achieve this difficult task in founding stem-history or phylogeny\nas an independent historical science in my \"General Evolution\" (in\nthe second volume of the _General Morphology_). With it I associated\nas a second and equally sound part ontogeny; I understood by this the\nwhole science of the development of the individual, both embryology and\nmetamorphology. Ontogeny enjoys the privileges (especially in the way\nof certainty) of a purely descriptive science, when it confines itself\nto the faithful description of the directly observed facts, either the\nembryonic processes in the womb or the later metamorphic processes.\nThe task of phylogeny is much more difficult, as it has to decipher\nlong-past processes by means of imperfect evidence, and has to use its\ndocuments with the utmost prudence.\n\nThe three most valuable sources of evidence in phylogeny are\npaleontology, comparative anatomy, and ontogeny. Paleontology seems\nto be the most reliable source, as it gives us tangible facts in\nthe fossils which bear witness to the succession of species in the\nlong history of organic life. Unfortunately, our knowledge of the\nfossils is very scanty and often very imperfect. Hence the numerous\ngaps in its positive evidence have to be filled up by the results of\ntwo other sciences, comparative anatomy and ontogeny. I have dealt\nfully with this in my _Anthropogeny_. As I have also spoken of the\ngeneral features of these phyletic evidences in the sixteenth chapter\nof the _History of Creation_, I need do no more here than repeat\nthat it is necessary to make equal and discriminating use of all\nthree classes of documents if we are to attain the aim of phylogeny\ncorrectly. Unfortunately, this necessitates a thorough knowledge of\nall three sciences, and this is very rare. Most embryologists neglect\npaleontology, most paleontologists embryology, while comparative\nanatomy, the most difficult part of morphology, involving most\nextensive knowledge and sound judgment, is neglected by both. Besides\nthese three sources of phylogeny there is valuable proof afforded\nby every branch of biology, especially by chorology, \u0153cology,\nphysiology, and biochemistry.\n\nAlthough there has been very extensive phylogenetic research during the\nlast thirty years, and it has yielded a number of interesting results,\nmany scientists still seem to look on them with a certain distrust;\nsome contest their scientific value altogether, and say that they are\nnothing but airy and untenable speculations. This is especially the\ncase with many physiologists who look upon experiment as the only\nexact method of investigation, and many embryologists who think their\nsole task is description. In view of these sceptical strictures, we\nmay recall the history and the nature of geology. No one now questions\nthe great importance and the various uses of this science, although\nin it there is no possibility of directly observing the historical\nprocesses as a rule. No scientist now doubts that the three vast\nsuccessive formations of the Mesozoic Period--the Triassic, Jurassic,\nand Cretaceous--have been formed from sea-deposits (lime, sandstone,\nand clay), though no one was a witness to the actual formation; no one\ndoubts to-day that the fossil skeletons of fishes and reptiles which\nwe find in these groups are not mysterious freaks of nature, but the\nremains of extinct fishes and reptiles that lived on the earth during\nthose millions of years long ago. And when comparative anatomy shows us\nthe genealogical connection of these related forms, and phylogeny (with\nthe aid of ontogeny) constructs their ancestral trees, their historical\nhypotheses are just as sound and reliable as those of geology; the\nonly difference is that the latter are much simpler, and thus easier\nto construct. Phylogeny and geology are, in the nature of the case,\n_historical sciences_.\n\nHypotheses are necessary in phylogeny and geology, where the empirical\nevidence is incomplete, as in every other historical science. It is no\ndetraction from the value of these to urge that they are sometimes weak\nand have to be replaced by better and stronger ones. A weak hypothesis\nis always better than none. We must, therefore, protest against the\nfoolish dread of hypotheses which is urged against our phylogenetic\nmethods by the representatives of the exact and descriptive sciences.\nThis shrinking from hypotheses often hides a defective knowledge of\nother sciences, an incapacity for synthetic thought, and a feeble sense\nof causality. The delusions into which it leads many scientists may be\nseen from the fact that chemistry, for instance, is reckoned an \"exact\"\nscience; yet no chemist has ever seen the atoms and molecules of\ncompounds with which he is occupied daily, or the complicated relations\non the assumption of which the whole of modern structural chemistry\nis based. All these hypotheses rest on inferences, not on direct\nobservation.\n\nI have, from the first, insisted on the close causal connection between\nontogeny and phylogeny, ever since I distinguished these two parts of\nbiogeny in the fifth book of the _General Morphology_. I also laid\nstress on the mechanical character of these sciences, and endeavored\nto give a physiological explanation of their morphological phenomena.\nUntil then embryology had been regarded as a purely descriptive\nscience. Carl Ernst Baer, who had provided a solid foundation for it\nin his classic _Animal Embryology_ (1828), was convinced that all the\nphenomena of individual development might be reduced to the laws of\ngrowth; but he was quite unconscious of the real direction of this\ngrowth, its \"purposiveness,\" the real causes of construction. The\ndistinguished W\u00fcrtzburg anatomist, Albert K\u00f6lliker, whose _Manual of\nHuman Embryology_ (1859) gave the first comprehensive treatment of the\nscience from the cellular point of view, adhered, even in the fourth\nedition (1884), to the opinion that \"the laws of the development of\nthe organism are still completely unknown.\" In opposition to this\ngenerally received opinion, I endeavored, in 1866, to prove that Darwin\nhad, by his improvement of the theory of descent, not only solved\nthe phylogenetic problem of the origin of species, but, at the same\ntime, given us the key to open the closed doors of embryology, and to\nlearn the causes of the ontogenetic processes as well. I formulated\nthis view in the twentieth chapter of the _General Morphology_, in\nforty-four theses, of which I will quote only the following three: 1.\nThe development of organisms is a physiological process, depending on\nmechanical causes, or physico-chemical movements. 40. Ontogenesis, or\nthe development of the organic individual, is directly determined by\nphylogenesis, or the evolution of the organic stem (_phylon_) to which\nit belongs. 41. Ontogenesis is a brief and rapid recapitulation of\nphylogenesis, determined by the physiological functions of heredity and\nadaptation. The pith of my biogenetic principle is expressed in these\nand the remaining theses on the causal nexus of biontic and phyletic\ndevelopment. At the same time I make it quite clear that I reduce the\nphysical process of ontogenesis, and also phylogenesis, to a pure\nmechanics of the plasm (in the sense of the critical philosophy).\n\nThe comprehensive fundamental law of organic development was briefly\nformulated by me in the fifth book of the _General Morphology_ and in\nthe tenth chapter of the _History of Creation_ (developed more fully\nin the fourteenth chapter of the tenth edition, 1902). I afterwards\nsought to establish it securely in two different ways. In the first\nplace, I proved in my _Studies of the Gastr\u00e6a Theory_ (1872-1877)\nthat in all the tissue-animals, from the lowest sponges and polyps to\nthe highest articulata and vertebrates, the multicellular organism\ndevelops from the same primitive embryonic form (the _gastrula_),\nand that this is the ontogenetic repetition, in virtue of heredity,\nof a corresponding stem-form (the _gastr\u00e6a_). In the second place, I\nmade the first attempt in my _Anthropogeny_ (1874) to illustrate this\nrecapitulation theory from the instance of our own human organism, by\ntrying to explain the complex process of individual development, for\nthe whole frame and every single part of it, by causal connection with\nthe stem-history of our animal ancestors. In the latest edition of this\nmonistic \"ontogeny of man\" I gave numbers of illustrations (thirty\nplates and five hundred engravings) of these intricate structures,\nand endeavored to make the subject still plainer by the addition of\nsixty genetic tables. I may refer the reader to this work,[10] and\nnot dwell any further here on the biogenetic law, especially as one\nof my pupils, Heinrich Schmidt (of Jena), has recently described its\nbiological significance and its earlier history and present position in\na very clear and reliable little work (_Haeckel's Biogenetic Law and\nits Critics_). I will only add a word or two on the struggle that has\ntaken place for thirty years over the complete or partial recognition\nof the biogenetic law, its empirical establishment, and its philosophic\napplication.\n\nIn the very name, \"fundamental law of biogeny,\" which I have given to\nmy recapitulation theory, I claim that it is universal. Every organism,\nfrom the unicellular protists to the cryptogams and c\u0153lenteria, and\nfrom these up to the flowering plants and vertebrates, reproduces in\nits individual development, in virtue of certain hereditary processes,\na part of its ancestral history. The very word \"recapitulation\"\nimplies a partial and abbreviated repetition of the course of the\noriginal phyletic development, determined by the \"laws of heredity\nand adaptation.\" Heredity brings about the reproduction of certain\nevolutionary features; adaptation causes a modification of them by\nthe conditions of the environment--a condensation, disturbance, or\nfalsification. Hence I insisted from the first that the biogenetic law\nconsists of two parts, one positive and palingenetic and the other\nrestrictively negative and cenogenetic. _Palingenesis_ reproduces a\npart of the original history of the stem; _cenogenesis_ disturbs or\nalters this picture in consequence of subsequent modifications of the\noriginal course of development. This distinction is most important, and\ncannot be too often repeated in view of the persistent misunderstanding\nof my opponents. It is overlooked by those who (like Plate and\nSteinmann) grant it only a partial validity, and by those who reject\nit altogether (like Keibel and Hensen). The embryologist Keibel is the\nmost curious of these, as he has himself afforded a good many proofs\nof the biogenetic law in his careful descriptive-embryological works.\nBut he has so little mastered it that he has never understood the\ndistinction between palingenesis and cenogenesis.\n\nIt is especially unfortunate that one of our most distinguished\nembryologists, Oscar Hertwig, of Berlin, who provided a good deal of\nevidence in favor of the biogenetic law thirty years ago, has lately\njoined the opponents of it. His supposed \"correction\" or modification\nof it is, as Keibel has rightly said, a complete abandonment of it.\nHeinrich Schmidt has partly explained the causes of this change\nin his work on the biogenetic law. They are not unconnected with\nthe psychological metamorphosis which Oscar Hertwig has undergone\nat Berlin. In the discourse on \"The Development of Biology in the\nNineteenth Century,\" which he delivered at the scientific congress at\nAachen in 1900, he openly accepted the dualist principles of vitalism\n(although he says they are \"just as unreliable as the chemico-physical\nconception of the opposing mechanical school\"). The views which he has\nlately advanced on the worthlessness of Darwinism and the unreliability\nof phylogenetic hypotheses are diametrically opposed to the opinions\nhe represented at Jena twenty-five years ago, and to those which his\nbrother, Richard Hertwig, of Munich, has consistently maintained in his\nadmirable _Manual of Zoology_.\n\nIn opposition to the mechanical ontogeny which I formulated in 1866\nand embodied in the biogenetic law, a number of other tendencies\nin embryology afterwards appeared, and, with the common title of\n\"mechanical embryology,\" branched out in every direction. The chief of\nthese to attract attention thirty years ago were the pseudo-mechanical\ntheories of Wilhelm His, who has rendered great service to ontogeny\nby his accurate descriptions and faithful illustrations of\nvertebrate-embryos, but who has no idea of comparative morphology,\nand so has framed the most extraordinary theories about the nature\nof organic development. In his _Study of the First Sketch of the\nVertebrate-body_ (1868), and many later works, His endeavored to\nexplain the complicated ontogenetic phenomena on direct and simple\nphysical lines by reducing them to elasticity, bending, folding of the\nembryonic layers, etc., while explicitly rejecting the phylogenetic\nmethod; he says that this is \"a mere by-way, and quite unnecessary for\nthe explanation of the ontogenetic facts (as direct consequences of\nphysiological principles of development).\" As a matter of fact, nature\nrather plays the part of an ingenious tailor in His's pseudo-mechanical\nand tectogenetic speculations, as I have shown in the third chapter of\nthe _Anthropogeny_. Hence they have been humorously called the \"tailor\ntheory.\" However, they misled a few embryologists by opening the way\nto a direct and purely mechanical explanation of the complex embryonic\nphenomena. Although they were at first much admired, and immediately\nafterwards abandoned, they have found a number of supporters lately in\nvarious branches of embryology.\n\nThe great success that modern experimental physiology achieved by its\nextensive employment of physical and chemical experiments inspired a\nhope of attaining similar results in embryology by means of the same\n\"exact\" methods. But the application of them in this science is only\npossible to a slight extent on account of the great complexity of the\nhistorical processes and the impossibility of \"exactly\" determining\nhistorical matters. This is true of both branches of evolution,\nindividual and phyletic. Experiments on the origin of species have\nvery little value, as I said before; and this is generally true of\nembryological experiments also. However, the latter, especially\ncareful experiments on the first stages of ontogenesis, have yielded\nsome interesting results, particularly in regard to the physiology\nand pathology of the embryo at the earliest stages of development.\nThe _Archiv f\u00fcr Entwickelungsmechanik_, which is edited by the chief\nrepresentative of this school, Wilhelm Roux, contains, besides these\nvaluable inquiries, a good number of ontogenetic articles, which partly\nrely on and partly ignore the biogenetic law.\n\nPsychology and biogeny have been up to the present regarded as the\nmost difficult branches of biology for monistic explanation, and the\nstrongest supports of dualistic vitalism. Both departments become\naccessible to monism and a mechanico-causal explanation by means\nof the biogenetic law. The close correlation which it establishes\nbetween individual and phyletic development, and which depends on the\ninteraction of heredity and adaptation, makes it possible to explain\nboth. In regard to the first, I formulated the following principle\nthirty years ago in my first study of the gastr\u00e6a theory: \"Phylogenesis\nis the mechanical cause of ontogenesis.\" This single principle clearly\nexpresses the essence of our monistic conception of organic development:\n\n In the future every student will have to declare himself for or\n against this principle, if in biogeny he is not content with a mere\n admiration of the wonderful phenomena, but desires to understand\n their significance. The principle also makes clear the wide gulf\n that separates the older teleological and dualistic morphology from\n the modern mechanical and monistic science. If the physiological\n functions of heredity and adaptation are proved to be the sole causes\n of organic construction, every kind of teleology, and of dualistic\n and metaphysical explanation, is excluded from the province of\n biogeny. The irreconcilable opposition between the leading principles\n of the two is clear. Either there is or is not a direct and causal\n connection between ontogeny and phylogeny. Either ontogenesis is a\n brief compendium of phylogenesis or it is not. Either epigenesis and\n descent--or pre-formation and creation.\n\nIn repeating these principles here, I would lay stress particularly on\nthe fact that, in my opinion, our \"mechanical biogeny\" is one of the\nstrongest supports of the monistic philosophy.\n\n\n\n\nXVII\n\nTHE VALUE OF LIFE\n\n Changes of life--Aim of life--Progress of life--Historic\n aims--Historic waves--Value of life in classes and races of\n men--Psychology of uncivilized races--Savages--Barbarians--Civilized\n nations--Educated nations--Three stages of development (lower,\n middle, and higher) in each of the four classes--Individual and\n social value of civilized life in the five sections of nutrition,\n reproduction, movement, sensation, and mental life--Estimate of human\n life.\n\n\nThe value of human life is seen by us to-day, now that evolution is\nestablished, in quite a different light from fifty years ago. We are\nnow accustomed to regard man as a natural being, the most highly\ndeveloped natural being that we know. The same \"eternal iron laws\"\nthat rule the evolution of the whole cosmos control our own life.\nMonism teaches that the universe really deserves its name, and is an\nall-embracing unified whole--whether we call it God or Nature. Monistic\nanthropology has now established the fact that man is but a tiny part\nof this vast whole, a placental mammal, developed from a branch of\nthe order of primates in the later Tertiary Period. Hence, before we\nseek to estimate the value of man's life, we will cast a glance at the\nsignificance of organic life generally.\n\nAn impartial survey of the history of organic life on our planet\nteaches, first of all, that it is a process of constant change.\nMillions of animals and plants die every second, while other millions\nreplace them; every individual has his definite period of life,\nwhether it lives only a few hours, like the one-day fly or the\ninfusorium, or, like the Wellingtonia, the dragon-tree of Orotava, and\nmany other giant trees, lives for thousands of years. Even the species,\nthe collection of like individuals, is just as transitory, and so are\nthe orders and classes that embrace numbers of species of animals and\nplants. Most species are confined to a single period of the organic\nhistory of the earth; few species or genera pass unchanged through\nseveral periods, and not a single one has lived in all the periods.\nPhylogeny, taking its stand on the facts of paleontology, teaches\nunequivocally that every specific living form has only existed a longer\nor shorter period in the course of the many (more than a hundred)\nmillion years which make up the history of organic life.\n\nEvery living being is an end to itself. On this point all unprejudiced\nthinkers are agreed, whether, like the teleologist, they believe in an\nentelechy or dominant as regulator of the vital mechanism, or whether\nthey explain the origin of each special living form mechanically by\nselection and epigenesis. The older anthropistic idea, that animals\nand plants were created for man's use, and that the relations of\norganisms to each other were generally regulated by creative design,\nis no longer accepted in scientific circles. But it is just as true of\nthe species as of the individual that it lives for itself, and looks\nabove all to self-maintenance. Its existence and \"end\" are transitory.\nThe progressive development of classes and stems leads slowly but\nsurely to the formation of new species. Every special form of life--the\nindividual as well as the species--is therefore merely a biological\nepisode, a passing phenomenal form in the constant change of life. Man\nis no exception. \"Nothing is constant but change,\" said the old maxim.\n\nThe historical succession of species and classes is, both in the\nanimal and the plant kingdom, accompanied by a slow and steady\nprogress in organization. This is directly and positively taught by\npaleontology; its creation-medals, the fossils, are unequivocal and\nirrefutable witnesses to this phylogenetic advance. I have dealt with\nthe subject in my _History of Creation_, and at the same time shown\nthat both the progressive improvement and the increasing variety of\nthe species can be explained mechanically as necessary consequences of\nselection. There was no need of a conscious Creator or a transcendental\npurposiveness to effect this. Scientific and thorough proof of this\nwill be found in the three volumes of my _Systematic Phylogeny_ (1894).\nI need only refer briefly to the two conspicuous examples we have in\nthe stem-history of the tissue-plants and that of the vertebrates. Of\nthe metaphyta the ferns are the chief groups in the Paleozoic, the\ngymnosperms in the Mesozoic, and the angiosperms in the Cenozoic age.\nOf the vertebrates only fishes are found in the Silurian age, dipneusta\nonly begin in the Devonian, and the first mammals are in the Triassic.\n\nA number of false teleological conclusions have been drawn from these\nfacts of progressive modification of forms, as they are given in\npaleontology. The latest and most developed form of each stem was\ntaken to be the preconceived aim of the series, and its imperfect\npredecessors were conceived as preparatory stages to the attainment\nof this aim. It was like the conduct of many historians, who, when\na particular race or state has reached a high rank in civilization\nas a result of its natural endowments and favorable conditions of\ndevelopment, hail it as a \"chosen people,\" and regard its imperfect\nearlier condition as a deliberately conceived preparatory stage.\nIn point of fact, these evolutionary stages were bound to proceed\naccording as the internal structure (given by heredity) and the outer\nconditions (provoking adaptation) determined. We cannot admit any\nconscious direction to a certain end, either in the form of theistic\npredestination or pantheistic finality. For this we must substitute a\nsimple mechanical causality in the sense of psycho-mechanical monism or\nhylozoism.\n\nAlthough the stem-history of plants and animals, like the history of\nhumanity, shows a progressive advance taken as a whole, we find a\ngood deal of vacillation in detail. These historical waves are wholly\nirregular; in periods of decay the hollows of the waves often persist\nfor a long time, and are then succeeded by a fresh rise to the crest\nof another wave. New and rapidly advancing groups come to take the\nplace of the old decaying groups, bringing with them a higher stage\nof organization. Thus, for instance, the ferns of to-day are only a\nfeeble survival of the huge and varied pteridophyta that formed the\nmost conspicuous part of the paleozoic forests in the Devonian and\nCarboniferous periods; they were ousted in the Secondary Period by\ntheir gymnosperm descendants (cycadea and conifers), and these, again,\nin the Tertiary Period by the angiosperm flowering plants. So among the\nterrestrial reptiles the modern tortoises, serpents, crocodiles, and\nlizards are only a feeble remnant of the enormous reptile-fauna that\ndominated the Secondary Period, the colossal dinosauri, pterosauri,\nichtyosauri, and plesiosauri. They were replaced in the Tertiary\nPeriod by the smaller but more powerful mammals. In the history of\ncivilization the Middle Ages form a deep valley between the crests of\nthe waves of classical antiquity and modern culture.\n\nThese few examples suffice to show that the various classes and orders\nof living things have a very different value when compared with each\nother. In regard to their intrinsic aim, self-maintenance, it is true\nthat all organisms are on a level, but in their relations to other\nliving things and to nature as a whole they are of very unequal\nvalue. Not only may larger animals and plants retain domination for a\nlong time in virtue of their special use or superior force and mass,\nbut small ones may prevail owing to their power of inflicting injury\n(bacteria, fungi, parasites, etc.). In the same way the value of the\nvarious races and nations is very unequal in human history. A small\ncountry like Greece has almost dominated the mental life of Europe\nfor more than two thousand years in virtue of its superior culture.\nOn the other hand, the various tribes of American Indians have, it is\ntrue, developed a partial civilization in some parts (Peru and Central\nAmerica); but, on the whole, they have proved incapable of advancing.\n\nThough the great differences in the mental life and the civilization\nof the higher and lower races are generally known, they are, as a\nrule, undervalued, and so the value of life at the different levels is\nfalsely estimated. It is civilization and the fuller development of the\nmind that makes civilization possible, that raise man so much above\nthe other animals, even his nearest animal relatives, the mammals. But\nthis is, as a rule, peculiar to the higher races, and is found only\nin a very imperfect form or not at all among the lower. These lower\nraces (such as the Veddahs or Australian negroes) are psychologically\nnearer to the mammals (apes or dogs) than to civilized Europeans; we\nmust, therefore, assign a totally different value to their lives. The\nviews on the subject of European nations which have large colonies in\nthe tropics, and have been in touch with the natives for centuries,\nare very realistic, and quite different from the ideas that prevail in\nGermany. Our idealistic notions, strictly regulated by our academic\nwisdom and forced by our metaphysicians into the system of their\nabstract ideal-man, do not at all tally with the facts. Hence we can\nexplain many of the errors of the idealistic philosophy and many of\nthe practical mistakes that have been made in the recently acquired\nGerman colonies; these would have been avoided if we had had a better\nknowledge of the low psychic life of the natives (_cf._ the writings of\nGobineau and Lubbock).\n\nThe grave errors that have been maintained in psychology for centuries\nare mostly due to a neglect of the comparative and genetic methods and\nthe narrow employment of self-observation, or the introspective method;\nthey are also partly due to the fact that metaphysicians generally make\ntheir own highly developed mind--a scientifically trained reason--the\nstarting-point of their inquiry, and regard this as representative of\nthe human mind in general, and thus build up their ideal scheme. The\ngulf between this thoughtful mind of civilized man and the thoughtless\nanimal soul of the savage is enormous--greater than the gulf that\nseparates the latter from the soul of the dog. Kant would have avoided\nmany of the defects of his critical philosophy, and would not have\nformulated some of his powerful dogmas (such as the immortality of the\nsoul, or the categorical imperative) if he had made a thorough and\ncomparative study of the lower soul of the savage, and phylogenetically\ndeduced the soul of civilized man therefrom.\n\nThe extreme importance of this comparison has only been fully\nappreciated of late years (by Lubbock, Romanes, etc.). Fritz Schultze\n(of Dresden) made the first valuable attempt in his interesting\n_Psychology of the Savage_ (1900) to give us an \"evolutionary\npsychological description of the savage in respect of intelligence,\n\u00e6sthetics, ethics, and religion.\" At the same time, he gives us \"a\nhistory of the natural creation of the human imagination, will, and\nfaith.\" The first book of this important work deals with thought, the\nsecond with will, and the third with the religious ideas of the savage,\nor \"the story of the natural evolution of religion\" (fetichism,\nanimism, worship of the heavenly bodies). In an appendix to the second\nbook the author deals with the difficult problems of evolutionary\nethics, supporting himself by the authority of the great work of\nAlexander Sutherland, _The Origin and Growth of the Moral Instinct_\n(1898). Sutherland divides humanity, in regard to the various stages of\ncivilization and mental development (not according to racial affinity),\ninto four great classes: 1, Savages; 2, barbarians; 3, civilized\nraces; 4, educated races. As this classification of Sutherland's not\nonly enables us to take a good survey of the various forms of mental\ndevelopment, but is also very useful in connection with the question of\nthe value of life at the different stages, I will briefly reproduce the\nchief points of his characterization of the four classes.\n\nI. SAVAGES.--Their food consists of wild natural products (the fruits\nand roots of plants, and wild animals of all kinds). Most of them are,\ntherefore, fishers or hunters. They are ignorant of agriculture and the\nbreeding of cattle. They live isolated lives in families or scattered\nin small groups, and have no fixed home. The lowest and oldest savages\ncome very close to the anthropoid apes from which they have descended,\nin bodily structure and habits. We may distinguish three orders in this\nclass--the lower, middle, and higher savages.\n\n_A._ Lower savages, approaching nearest to the ape, pygmies of\nsmall stature, four to four and a half feet high (rarely four and\nthree-quarters); the women sometimes only three to three and a half\nfeet. They are woolly haired and flat-nosed, of a black or dark brown\ncolor, with pointed belly, thin and short legs. They have no homes, and\nlive in forests and caverns, and partly on trees; wander about in small\nfamilies of ten to forty persons; quite naked, or with just a trace of\nsome primitive garment. Of the lower races now living we must put in\nthis class the Veddahs of Ceylon, the Semangs of the Malay Peninsula,\nthe Negritos of the Philippines, the Andaman Islanders, the Kimos of\nMadagascar, the Akkas of Guinea, and the Bushmen of South Africa. Other\nscattered remnants of these ancient negroid dwarfs, which approach\nclosely to the anthropoid apes, still live in various parts of the\nprimitive forests of the Sunda Islands (Borneo, Sumatra, Celebes).\n\nThe value of the life of these lower savages is like that of the\nanthropoid apes, or very little higher. All recent travellers who have\ncarefully observed them in their native lands, and studied their bodily\nstructure and psychic life, agree in this opinion. Compare the thorough\ntreatment of the Veddahs of Ceylon in the work of the brothers Sarasin\n(of which I have given a summary in my _Travels in Ceylon_). Their only\ninterests are food and reproduction, in the same simple form in which\nwe find these among the anthropoid apes (_cf._ chapters xv. and xxiii.\nof my _Anthropogeny_). Our own ancestors were probably much the same\nten thousand or more years ago. On the strength of fossil remains of\nPleistocene men Julius Kollmann has shown it to be very probable that\nsimilar dwarf races (with an average height of four and a half feet)\ninhabited Europe at that time.\n\n_B._ Middle savages, somewhat larger and less apelike than the\npreceding, averaging five to five and a half feet in height. Their\nhomes are rock caverns and shelters from the wind and rain. Though\nthey have shirts and other rudiments of clothing, both sexes generally\ngo naked; they have primitive weapons of wood and stone and rudely\nfashioned boats, wander in troops of fifty to two hundred, and have\nno social organization; certain races, however, have laws. To this\ngroup belong the Australian negroes and Tasmanians, the Ainos of\nJapan, the Hottentots, Fuegians, Macas, and some of the forest races of\nBrazil. The value of their life is very little superior to that of the\npreceding order.\n\n_C._ Higher savages, mostly of average human height (smaller in colder\nregions), having always simple dwellings (generally of skins or the\nbark of trees). They have always primitive clothing, and good weapons\nof stone, bronze, or copper. They wander in troops of one hundred to\nfive hundred, led by prominent but not ruling princes, and exhibiting\nrudimentary differences of rank. The method of life is determined\nby hereditary customs. To this group belong many of the primitive\ninhabitants of India (Todas, Nagas, Curumbas, etc.), the Nicobar\nIslanders, the Samoyeds, and Kamtschadals; in Africa, the negroes of\nDamara; and most of the Indian tribes of North and South America. Their\nlife is higher than that of the pithecoid lower and middle savages, but\nless than that of the barbarians.\n\nII. BARBARIANS OR SEMI-SAVAGES.--The greater part of their food\nconsists of natural products, which they secure with some foresight;\nhence they have developed agriculture and pasture to a greater or less\nextent. The division of labor is slight, each family supplying its\nown wants. As a rule, a stock of food is provided for the whole year.\nAs a result of this, art begins to develop. They have generally fixed\ndwellings.\n\n_A._ Lower Barbarians. Dwellings: Simple huts, generally grouped into\nvillages and surrounded with plantations. Clothing worn regularly, but\nvery simple: the men often naked in hot climates or with shirt. Pottery\nand cooking utensils, tools of stone, wood, or bone. Rudiments of\ncommerce by exchange. Groups of one thousand to five thousand persons\nable to form larger communities; distinctions of rank and warfare.\nPrinces rule according to traditional laws. Of this group we have\nin Asia many of the aboriginal inhabitants of India (Mundas, Khonds,\nPaharias, Bheels, etc.), the Dyaks of Borneo, the Battaks of Sumatra,\nTunguses, Kirgises, etc.; in Africa the Kaffirs, Bechuanas, and\nBasutos; in Australasia the aborigines of New Guinea, New Caledonia,\nNew Hebrides, New Zealand, etc.; and in America the Iroquois and\nThlinkets, and the inhabitants of Nicaragua and Guatemala.\n\n_B._ Middle barbarians. Dwellings good and durable, generally of wood,\nroofed with cane or straw, forming fine towns. Clothing general, though\nnudity is not considered immoral. Pottery, weaving, and metal-work\npretty well developed. Commerce in regular markets, with the use of\nmoney. States ruled by kings in accordance with traditional laws,\nfixed distinctions of rank, communities up to one hundred thousand\npersons. To these belong in Asia the Calmucks; in Africa many negro\nraces (Ashantis, Fantis, Fellahs, Shilluks, Mombuttus, Owampos, etc.);\nin Polynesia the inhabitants of the Fiji, Tonga, Samoa, and Markesas\nislands. In Europe the Lapps belonged to this class two hundred years\nago, the ancient Germans two thousand years ago, the Romans before\nNuma, and the Greeks of the Homeric period.\n\n_C._ Higher barbarians. Dwellings, usually solid stone buildings.\nClothing obligatory, weaving habitual occupation of the women,\nmetal-work far advanced, tools generally of iron. Restricted commerce,\nwith minted money, no rudder-ships. Crude judicature in fixed courts;\nrudimentary writing. Masses of people, with progressive division of\nlabor and hereditary distinctions of rank, sometimes reaching half a\nmillion souls, under an autonomous ruler. To this class belong in Asia\nmost of the Malays (in the large Sunda Islands and the peninsula of\nMalacca), and the nomadic races of Tartars, Arabs, etc.; in Polynesia\nthe islanders of Tahiti and Hawaii; in Africa the Somalis and\nAbyssinians, and the inhabitants of Zanzibar and Madagascar. Of the\nhistoric peoples of antiquity we have the Greeks of the time of Solon,\nthe Romans at the beginning of the republic, the Jews under the Judges,\nthe Anglo-Saxons of the Heptarchy, and the Mexicans and Peruvians at\nthe time of the Spanish invasion.\n\nIII. CIVILIZED RACES.--Food and complex vital needs are easily\nsatisfied on account of the advanced division of labor and improvement\nof instruments. Art and science are consequently developed more and\nmore. The increasing specialization brings about a great elaboration\nof individual functions, and at the same time a great strengthening of\nthe whole body politic, as there is complete mutual dependence. The\ncitizens see that they must submit to the laws of the state.\n\n_A._ Lower civilized races. Towns with stone walls; vast architectural\nworks in stone; use of the plough in agriculture. War is intrusted to\na particular class. Writing firmly established, primitive law-books,\nfixed courts. Literature begins to develop. To this group belong\nin Asia the inhabitants of Thibet, Bhutan, Nepaul, Laos, Annam,\nKorea, Manchuria, and the settled Arabs and Turcomans; in Africa the\nAlgerians, Tunisians, Moors, Kabyles, Tuaregs, etc. Of historical races\nwe have the ancient Egyptians, Ph\u0153nicians, Assyrians, Babylonians,\nCarthaginians, the Greeks after Marathon, the Romans of the time of\nHannibal, and the English under the Norman kings.\n\n_B._ Middle civilized races. Beautiful temples and palaces, built\nof stone and brick. Windows come into use, and sailing-ships.\nCommerce expands. Writing and written books are general; the literary\ninstruction of the young is attended to. Militarism is further\ndeveloped; so are legislation and advocacy. Of these we have in Asia\nthe Persians, Afghans, Birmans, and Siamese; in Europe the Finns and\nMagyars of the eighteenth century. Of historical peoples we must count\namong them the Greeks of the age of Pericles, the Romans of the later\nrepublic, the Jews under the Macedonian rule, France under the first\nCapets, and England under the Plantagenets.\n\n_C._ Higher civilized races. Stone houses general; streets paved;\nchimneys, canals, water and wind mills. Beginnings of scientific\nnavigation and warfare. Writing general, written books widely\ndistributed, literature esteemed. The highly centralized state embraces\ncommunities of ten millions or more. Fixed and written codes of law\nare officially promulgated and applied by courts to particular cases.\nNumbers of government officials have settled rank. To this group belong\nin Asia the Chinese, Japanese, and Hindoos; also the Turks and the\nvarious republics of South America, etc. In history we have the Romans\nof the empire, and the Italians, French, English, and Germans of the\nfifteenth century.\n\nIV. CULTIVATED RACES.--Food and other needs are artificially supplied\nwith the greatest ease and in abundance, human labor being replaced\nby natural forces. The social organization grows and facilitates the\nplay of all the social forces, and man obtains a great freedom to\ncultivate his mental and \u00e6sthetic qualities. Printing is in general\nuse, the education of the young one of the first duties. War becomes\nless important; rank and fame depend less on military bravery than on\nmental superiority. Legislation is influenced by representatives of the\npeople. Art and science are increasingly promoted by state aid.\n\nAlexander Sutherland distinguishes three stages of development--the\nlower, middle, and higher--in the fourth as well as in the preceding\nclasses. To the first stage he assigns \"the leading nations of Europe\nand their offshoots, such as the United States of North America.\"\nFor the second stage--middle cultured races--he gives a programme\nthat may be carried out in three or four hundred years' time, with\nthis definition: \"All men are well fed and housed; war is universally\ncondemned, but breaks out now and again. Small armies and fleets of all\nthe nations co-operate as a sort of international police; commercial\nand industrial life are directed according to the moral precepts of\nsympathy; culture is general; crime and punishment rare.\" Of the third\nand highest stage Sutherland merely says, \"Too bold a subject for\nprophecy, that may not come for one thousand to two thousand years\nyet.\" This division seems to me too vague and unsatisfactory, in the\nsense that it does not properly emphasize the civilization of the\nnineteenth century in contrast with all preceding stages. It would\nbe better to distinguish _provisionally_ the following stages in\nmodern civilization: first, sixteenth to eighteenth century; second,\nnineteenth century; and third, twentieth century and the future.\n\n_A._ Lower cultured races (Europe, sixteenth to eighteenth century).\nAt the commencement of this period, the first half of the sixteenth\ncentury, we notice the preparatory movements to the full growth of\nmental life which was to achieve such great results in the following\nperiods: 1. The cosmic system of Copernicus (1543) maintained by\nGalileo (1592). 2. The discovery of America by Columbus (1492) and of\nthe East Indies by Vasco da Gama (1498), the first circumnavigation\nof the earth by Magellan (1520) and the evidence it afforded of the\nrotundity of the earth. 3. The liberation of the mind of Europe\nfrom the papal yoke by Martin Luther (1517) and the repulse of the\nprevailing superstition by the spread of the Reformation. 4. The new\nimpulse to scientific investigation independently of scholasticism\nand the Church and of the philosophy of Aristotle; the founding of\nempirical science by Francis Bacon (1620). 5. The spread of scientific\nknowledge by the press (Gutenberg, 1450) and wood-engraving. The way\nwas prepared for modern civilization by these and other advances in the\nsixteenth century, and it quickly arose above the barbaric level of the\nMiddle Ages. However, it was confined at first within narrow limits, as\nthe reactionary civilization of the Middle Ages was still powerful in\npolitical and social life, and the struggle against superstition and\nunreason made slow progress. The French Revolution (1792) at last gave\na great impetus in practical directions.\n\n_B._ Middle cultured races. This name may be given to the leading\nnations of Europe and North America in the nineteenth century. We may\nillustrate in the following achievements the great advance which this\n\"century of science\" made as compared with all preceding ages: 1.\nDeepening, experimental grounding, and general spread of a knowledge\nof nature; independent establishment of many new branches of science;\nfounding of the cell-theory (1838), the law of energy (1845), and the\ntheory of evolution (1859). 2. Practical and comprehensive application\nof this theoretical science to all branches of art and industry.\nEspecially 3. The overcoming of time and space by the extraordinary\nspeed of transit (steamboats, railways, telegraphs, electrotechnics).\n4. Construction of the monistic and realistic philosophy, in opposition\nto the prevailing dualistic and mystical views. 5. Increasing influence\nof rational scientific instruction and abandonment of the religious\nfiction of the Churches. 6. Increasing self-consciousness of the\nnations on account of having a share in government and legislation;\nextinction of the belief in the divine right of rulers. New distinction\nof classes. However, these great advances, to which we children of the\nnineteenth century may point with pride, are far from being universal;\nthey are struggling daily with reactionary views and powers in Church\nand state, with militarism, and with ancient and venerable immorality\nof every kind.\n\n_C._ The higher culture which we are just beginning to glimpse will set\nitself the task of creating as happy and contented a life as possible\nfor all men. A perfect ethic, free from all religious dogma and based\non a clear knowledge of natural law, will be found in the golden rule,\n\"Love thy neighbor as thyself.\" Reason tells us that a perfect state\nmust provide the greatest possible happiness for every individual that\nbelongs to it. The adjustment of a rational balance between egoism and\naltruism is the aim of our monistic ethics. Many barbaric customs that\nare still regarded as necessary--war, duelling, ecclesiastical power,\netc.--will be abolished. Legal decisions will suffice to settle the\nquarrels of nations, as they now do of individuals. The chief interest\nof the state will be, not the formation of as strong a military force\nas possible, but the best possible instruction of its young, with\nspecial attention to art and science. The improvement of technical\nmethods, owing to new discoveries in physics and chemistry, will bring\ngreater satisfaction of our needs of life. The artificial production of\nalbumin will provide plenty of food for all. A rational reform of the\nmarriage relations will increase the happiness of family life.\n\nThe darker sides of modern life, of which we are all more or less\nsensitive, have been laid bare by Max Nordau in his _Conventional Lies\nof Civilization_. They will be greatly altered if reason is permitted\nto have its way in practical life, and the present evil customs, based\non antiquated dogmas, are suppressed. But, in spite of all these\nshades, the luminous features of modern civilization are so great that\nwe look to the future with hope and confidence. We need only glance\nback half a century, and compare life to-day with what it was then,\nin order to realize the progress made. If we regard the modern state\nas an elaborate organism (a \"social individual of the first order\"),\nand compare its citizens to the cells of a higher tissue-animal, the\ndifference between the state of to-day and the crudest family groups\nof savages is not less than that between a higher metazoon (such as a\nvertebrate) and a c\u0153nobium of protozoa. The progressive division\nof labor, on the one hand, and the centralization of society, on the\nother, prepare the social body for higher functions than in isolation,\nand proportionately increase the worth of its life. To see this more\nclearly, let us compare the personal and the social value of life in\nthe five chief fields of vital activity--nutrition, reproduction,\nmovement, sensation, and mental life.\n\nThe first need of the individual organism, self-maintenance, is met in\na much more perfect manner in the modern state than it was formerly.\nThe savage is satisfied with the raw products of nature--with hunting,\nfishing, and the gathering of roots and fruits. Agriculture and\npasturage come later. Many stages of barbarism and lower civilization\nmust be passed before the conditions of feeding, housing, and clothing\nprovide a secure and comfortable existence for man, and permit the\naddition of \u00e6sthetic and intellectual interests to the indispensable\nsearch for food.\n\nThe feeding and condition of the social body as a whole have been\nimproved by modern civilization, just as in the case of the individual.\nThe progress of chemistry and agriculture has enabled us to produce\nfood in larger quantities. The ease and rapidity of transfer allow it\nto be distributed over the whole earth. Scientific medicine and hygiene\nhave discovered many means of diminishing the dangers of disease and\npreventing its occurrence. By means of public baths, gymnasiums,\npopular restaurants, public gardens, etc., greater care is taken of\nthe health of the community. The arrangement of modern houses and\ntheir heating and lighting have been immensely improved. Modern social\npolitics strives more and more to extend these benefits of civilization\nto the lower classes. Philanthropic societies are busy supplying the\nmaterial and spiritual wants of various classes of sufferers. It is\ntrue there is still a broad margin for the improvement of the national\nwell-being. But, on the whole, it cannot be denied that the provision\nof food in the modern state is an immense advance upon that of the\nMiddle Ages and of the barbaric period.\n\nThe great value of modern civilization and its vast progress beyond\nthe condition of the savage is seen in no branch of physiology so\nconspicuously as in the wonderful process of reproduction and the\nmaintenance of the species. In most savages and barbarians the\nsatisfaction of their powerful sexual impulse is at the same low stage\nas in the ape and other mammals. The woman is merely an object of\nlust to the man, or even a slave without rights, bought and exchanged\nlike all other property. Improvement is slow and gradual in the value\nof this property, until it reaches a high guarantee of permanency in\nthe formal marriage. The family life proves a source of higher and\nfiner enjoyment for both parties. The position of woman advances with\ncivilization; her rights obtain further recognition, and in addition to\nsensual love the psychic relation of man and wife begins to develop.\nThe common concern for the proper care and education of the children,\nwhich we find to an extent even in the case of many animals, leads\nto the further development of family life and the founding of the\nschool. With the advent of a higher stage of civilization begins the\nrefinement of sexual love, which finds its highest satisfaction, not in\nthe momentary gratification of the sex-impulse, but in the spiritual\nrelation of the sexes and their constant and intimate intercourse. The\nbeautiful then unites with the good and the true to form a harmonious\ntrinity. Hence love has been for thousands of years the chief source\nof the \u00e6sthetic uplifting of man in every respect; the arts--poetry,\nmusic, painting, and sculpture--have drawn inexhaustively from this\nsource. However, for the individual civilized human being this\nhigher love is of value, not only because it satisfies the natural\nand irresistible sex-impulse in its noblest form, but also because\nthe mutual influence of the sexes, their complementary qualities and\ntheir common enjoyment of the highest ideal good, has a great effect\nupon individual character. A good and happy marriage--which is not\nvery common to-day--ought to be regarded, both psychologically and\nphysiologically, as one of the most important ends of life by every\nindividual of the higher nations.\n\nAs a pure marriage is the best form of family life and the most solid\nfoundation of the state, its high social value is at once evident. The\nattraction and mutual devotion of the sexes fulfils in the highest\ndegree the ethical golden rule--the balance of egoism and altruism. As\nFritz Schultze very truly says in his _Comparative Psychology_\n\n We must not seek the causes of this altruism in the transcendental\n region of the supernatural, or in any metaphysical abstraction,\n but must go back to the very real and natural qualities of the\n organic being--and then there can be no question that the organic\n sex-impulse, at once physical and psychical is the first and enduring\n source of all love, however spiritual, and of all real ethical and\n sympathetic feelings and the morality founded thereon. There are\n two primitive instincts in all organisms: that of self-maintenance\n and that of the maintenance of the species. The one is the strong\n impulse of egoism, the other the spring of altruism: from the one\n come all unfriendly and from the other all friendly feelings. Every\n being seeks first to nourish and protect itself in virtue of its\n instinct of self-maintenance. But soon the magic of the instinct for\n the maintenance of the species works in it; it feels the sex-impulse,\n and thinks it is only satisfying its egoistic lust in yielding to\n it. In this it is wrong; it is not really serving itself, but the\n whole, the species, the genus. The ardor of love burns in it; and\n however sensual this love is at first, the new feeling is undeniably\n a feeling of belonging to another and of mutual consideration,\n looking not only to itself, but to another; not only to its own good,\n but to that of another, and finding its own good only in that of the\n other. And though this feeling at first only unites the two parents,\n it enlarges when children enter into life, and is extended to them\n in the form of parental love. Thus, out of the sex-impulse of the\n maintenance of the species, with its strong physical and psychic\n roots, is developed the love of spouses, of parents, of children,\n and of neighbor. Disinterested egoism goes even to the extent of\n sacrificing its own life for its young; in this organic and natural\n family love, and in the sense of the family that comes of it, we find\n the roots of all sympathetic and really ethical altruistic feelings;\n from this it widens out to larger spheres. Hence, the family is\n rightly held to be the chief source of all real moral feeling and\n life, not only in the human, but also in the animal world.\n\nThe further ennoblement of family life in the advance of civilization\nwill give fresh proofs of the truth of this appreciation.\n\nWe now turn to consider the advantages that modern civilization offers\nin the way of movement in contrast to the simple methods of locomotion\nof the savage. We may point out first that the earliest men, like their\nancestors, the anthropoid apes, lived in trees, and only gradually\nbegan to run on the ground. Some of the higher savages began to use\nthe horse for riding and to tame it. Many inhabitants of the coast or\nislands began at an early period to make boats. Later the barbaric\ntribes invented the wagon, and much later again streets were paved\nand vehicles improved by civilized races. But the nineteenth century\nbrought the invaluable means of rapid and convenient travelling by\nmeans of steamboats and railways. The whole problem of transit was\nrevolutionized, and in the last few decades further vast changes have\nbeen made owing to the advance of electricity. Modern ideas of time\nand space are quite different from those of our parents sixty years\nago, or our grandparents ninety years ago. In our expresses we cover\nin an hour a stretch of country that the mail-coach took five times\nand the foot-passenger ten times as long to cover. As the experiments\nwith the Berlin electric railway have lately shown, we can now travel\ntwo hundred kilometres in an hour. The journey from Europe to India\nnow takes three weeks, whereas the earlier sailing-vessel took as\nmany months. The immense saving of time that we make is equivalent to\na lengthening of our own life. This applies also to the more rapid\ntransit provided by balloons, automobiles, bicycles, etc. It is easy\nto estimate the value of these improvements; but it is only fully\nappreciated by those who have lived long in an uncivilized country\nwithout roads or among savages whose legs are their only means of\nlocomotion.\n\nThis progress in the means of transit is not less valuable socially\nthan personally. If we conceive the state as a unified organism of the\nhigher order, the development of its means of transit corresponds in\nmany ways to that of the circulation of the blood in the vertebrate\nframe. The easy, rapid, and convenient transport of the means of\nlife from the centre to the most distant parts of the land, and the\ncorresponding development of the net-work of railways and steamboat\nroutes, are to a certain extent direct tests of the degree of\ncivilization. To this we must add the creation of a large number of\noffices which provide steady employment and means of subsistence for\nmany thousands.\n\nTo compare the complex sensations of civilized man with the much\nsimpler ones of the savage we must consider first the functions of\nthe outer organs of sense and then the internal sense-processes in the\ncortex of the brain. Fritz Schultze has pointed out in his _Psychology\nof the Savage_, in regard to both sets of organs, that the savage is\na man of sense-life, the civilized human being a man of mind-life.\nWhen we remember that our higher psychic functions (sensation, will,\npresentation, and thought) are anatomically connected with the phronema\n(the thought-organ in the cortex), and the inner sense-perception\nwith the central sensorium (in the sense-centres of the cortex), we\nshall expect to find the latter more developed in the savage and the\nformer in civilized man. The external sense-action is more intense in\nquantity, but weaker in quality, in the savage than in civilized man;\nthis is especially true of the finer and more complex sense-functions\nwhich we call \u00e6sthetic sensations and regard as the source of art and\npoetry. Most strongly developed of all in the savage is the power of\nperceiving distant objects (sight, hearing, smell), as they warn him of\nthe dangers about him. It is just the reverse with the subjective and\nproximate feelings that are excited by the immediate touch of objects\nand are the special instruments of sensual enjoyment--taste, sex-sense,\ntouch, and feeling of temperature. But in both kinds of sense-action\nthe civilized man is far ahead of the savage in respect of the finer\nshades of feeling and \u00e6sthetic education. Moreover, modern civilization\nhas provided man with various means of vastly increasing and improving\nthe natural power of his senses. We need only mention the fields of\nknowledge that have been opened to us by the microscope and telescope,\nthe refined chemical methods of modern cooking, etc. The finer \u00e6sthetic\nenjoyment which our advanced art affords--plastic art for the eye,\nmusic for the ear, perfumery for the nose, cuisine for the tongue--is\ngenerally unintelligible to the savage, although he can see much\nfarther, and hear and smell much more acutely, than civilized man. And\nin the senses of near objects (taste, touch, temperature) the senses of\nthe savages are more coarse, and incapable of the fine gradations of\ncivilized man.\n\nThis more refined sense-life and the accompanying \u00e6sthetic enjoyment\nhave no less social than personal value. We have, in the first place,\nthe incalculable treasure of modern art and science, their promotion\nby the state, and their embodiment in the training of the young. In\nthe future the higher races are likely to give more attention to this,\ntraining the senses of children as well as their intelligence from the\nearliest years, leading them to a closer observation of nature and\nreproduction of its forms by drawing and painting. The art-sense must\nalso be fostered by the exhibition of models and by \u00e6sthetic exercises,\na larger place must be given to artistic education along with the\nacquisition of real knowledge, and an appreciation of the beauties of\nnature must be created by means of walks and travels. Then the children\nof civilized races will have the inexhaustible sources of the finest\nand noblest pleasures in life opened to them in good time.\n\nThe higher psychic activity that civilized man calls his \"mental life,\"\nand that is so often regarded as a kind of miracle, is merely a higher\ndevelopment of the psychic function we find at a lower level in the\nsavage, and is shared by him with the higher vertebrates. Comparative\npsychology shows us, as I have explained in the seventh chapter of the\n_Riddle_, the long scale of development, which leads from the simple\ncell-soul of the protist up to the intelligence of man. I have already\ndealt in various chapters with this point, and need not enlarge on\nit any further to estimate the high personal value of mental life in\nevery civilized human being. It is enough to remind the reader of\nthe vast treasures of knowledge that lie open to every one of us at\nthe commencement of the twentieth century--treasures of which our\ngrandparents at the beginning of the last century had not the slightest\npresentiment.\n\nJust as the individual has experienced a great advance in the value\nof his personal life by the higher culture of the nineteenth century,\nso the modern state itself has benefited by it in many ways. The many\ndiscoveries made in every branch of science and technical industry, the\ngreat advance in commerce and industrial life, in art and science, were\nbound to bring about a higher development of the whole mind of a modern\ncommunity. Never, in the whole of history, has true science risen to\nsuch an astounding height as it has at the beginning of the twentieth\ncentury. Never before did the human mind penetrate so deeply into the\ndarkest mysteries of nature, never did it rise so high to a sense of\nthe unity of nature and make such practical use of its knowledge. These\nbrilliant triumphs of modern civilization have, however, only been\nmade possible by the various forces co-operating in a vast division of\nlabor, and by the great nations utilizing their resources zealously for\nthe attainment of the common end.\n\nBut we are still far from the attainment of the ideal. The social\norganization of our states is advanced only on one side; it is very\nreactionary on other sides. Unfortunately, the words of Wallace which\nI quoted in the _Riddle_ remain as true as ever. Our modern states\nwill only pass beyond this condition in the course of the twentieth\ncentury if they adopt pure reason as their guide instead of faith and\ntraditional authority, and if they come at length to understand aright\n\"man's place in nature.\"\n\nIf we take a summary view of all that I have said on the increase in\nthe value of human life by the progress of civilization, there can be\nno doubt that both the personal and the social value of life are now\nfar higher than they were in the days of our savage ancestors. Modern\nlife is infinitely rich in the high spiritual interests that attach\nto the possession of advanced art and science. We live in peace and\ncomfort in orderly social and civic communities, which have every\ncare of person and property. Our personal life is a hundred times\nfiner, longer, and more valuable than that of the savage, because it\nis a hundred times richer in interests, experiences, and pleasures.\nIt is true that within the limits of civilization the differences in\nthe value of life are enormous. The greater the differentiation of\nconditions and classes in consequence of division of labor, the greater\nbecome the differences between the educated and uneducated sections of\nthe community, and between their interests and needs, and, therefore,\nthe value of their lives. This difference is naturally most conspicuous\nif we consider the leading minds and the greatest heights of the\nculture of the century, and compare these with the average man and the\nmasses, which wander far below in the valley, treading their monotonous\nand weary way in a more or less stupid condition.\n\nThe state thinks quite otherwise than the individual man does of the\npersonal worth of his life and that of his fellows. The modern state\noften demands for its protection the military service of all its\ncitizens. In the eyes of our ministers of justice the value of life\nis the same whether there be question of an embryo of seven months\nor a new-born child (still without consciousness), an idiot or a\ngenius. This difference between the personal and the social estimate\nof life runs through the whole of our moral principles. War is still\nbelieved by highly civilized nations to be an unavoidable evil, just as\nbarbarians think of individual murder or blood-revenge; yet the murder\nof masses for which the modern state uses its greatest resources is in\nflagrant contradiction to the gentle doctrine of Christian charity\nwhich it employs its priests to preach every Sunday with all solemnity.\n\nThe chief task of the modern state is to bring about a natural\nharmony between the social and the personal estimate of human life.\nFor this purpose we need, above all, a thorough reform of education,\nthe administration of justice, and the social organization. Only\nthen can we get rid of that medi\u00e6val barbarism of which Wallace\nspeaks; to-day it finds expression triumphantly in our penal laws,\nour caste-privileges, the scholastic nature of our education, and the\ndespotism of the Church.\n\nFor each individual organism the life of the individual is the first\naim and the standard of value. On this rests the universal struggle\nfor self-maintenance, which can be reduced in the inorganic world to\nthe physical law of inertia. To this subjective estimate of life is\nopposed the objective, which proceeds on the value of the individual\nto the outer world. This objective value increases as the organism\ndevelops and presses into the general stream of life. The chief of\nthese relations are those that come of the division of labor among\nindividuals and their association in higher groups. This is equally\ntrue of the cell-states which we call tissues and persons, of the\nhigher stocks of plants and animals, and of the herds and communities\nof the higher animals and men. The more these develop by progressive\ndivision of labor and the greater the mutual need of the differentiated\nindividuals, so much the higher rises the objective value of the life\nof the latter for the whole, and so much the lower sinks the subjective\nvalue of the individual. Hence arises a constant struggle between the\ninterests of individuals who follow their special life-aim and those of\nthe state, for which they have no value except as parts of the whole.\n\n\n\n\nXVIII\n\nMORALITY\n\n Dualistic ethics--The categorical imperative--Monistic ethics--Morals\n and adaptation--Variation and adaptation--Habit--Chemistry of\n habit--Trophic stimuli--Habit in inorganic bodies--Instincts--Social\n instincts--Instinct and morality--Right and duty--Morals and\n morality--The good and the bad--Morals and fashions--Sexual\n selection--Fashion and the feeling of shame--Fashion and\n reason--Ceremonies and cults--Mysteries and sacraments--Baptism--The\n Lord's Supper--Transubstantiation--The miracle of redemption--Papal\n sacraments--Marriage--Modern fashions--Honor--Phylogeny of morals.\n\n\nThe practical life of man is, like that of all the social higher\nanimals, ruled by impulses and customs which we describe as \"moral.\"\nThe science of morality, ethics, is regarded by the dualists as a\nmental science, and closely connected with religion on the one hand and\npsychology on the other. During the nineteenth century this dualistic\nview retained its popularity especially because the great authority\nof Kant, with his dogma of the categorical imperative, seemed to have\ngiven it a solid foundation, and because it agreed admirably with the\nteaching of the Church. Monism, on the other hand, regards ethics as\na natural science, and starts from the principle that morality is not\nsupernatural in origin, but has been built up by adaptation of the\nsocial mammals to the conditions of existence, and thus may be traced\neventually to physical laws. Hence modern biology sees no metaphysical\nmiracle in morality, but the action of physiological functions.\n\nOur whole modern civilization clings to the erroneous ideas which\ntraditional morality, founded on revelation, and closely connected\nwith ecclesiastical teaching, has imposed upon it. Christianity has\ntaken over the ten commandments from Judaism, and blended them with a\nmystical Platonism into a towering structure of ethics. Kant especially\nlent support to it in recent years with his _Critique of Practical\nReason_, and his three central dogmas. The close connection of these\nthree dogmas with each other, and their positive influence on ethics,\nwere particularly important through Kant formulating the further dogma\nof the categorical imperative.\n\nThe great authority which Kant's dualist philosophy obtained is largely\nowing to the fact that he subordinated pure reason to practical reason.\nThe vague moral law for which Kant claimed absolute universality is\nexpressed in his categorical imperative as follows: \"So act that the\nmaxim (or the subjective principle of your will) may at the same time\nserve as a general law.\" I have shown in the nineteenth chapter of the\n_Riddle_ that this categorical imperative is, like the thing in itself,\nan outcome of dogmatic, not critical, principles. As Schopenhauer says:\n\n Kant's categorical imperative is generally quoted in our day under\n the more modest and convenient title of \"the moral law.\" The daily\n writers of compendiums think they have founded the science of ethics\n when they appeal to this apparently innate \"moral law,\" and then\n build on it that wordy and confused tissue of phrases with which\n they manage to make the simplest and clearest features of life\n unintelligible, without having ever seriously asked themselves\n whether there really is any such convenient code of morality written\n in our head, breast, or heart. This broad cushion is snatched from\n under morality when we prove that Kant's categorical imperative\n of the practical reason is _a wholly unjustified, baseless, and\n imaginative assumption_.\n\nKant's categorical imperative is a mere dogma, and, like his whole\ntheory of practical reason, rests on dogmatic and not critical grounds.\nIt is a fiction of faith, and directly opposed to the empirical\nprinciples of pure reason.\n\nThe notion of duty, which the categorical imperative represents as\na vague _a priori_ law implanted in the human mind--a kind of moral\ninstinct--can, as a matter of fact, be traced to a long series of\nphyletic modifications of the phronema of the cortex. Duty is a\nsocial sense that has been evolved _a posteriori_ as a result of the\ncomplicated relations of the egoism of individuals and the altruism of\nthe community. The sense of duty, or conscience, is the amenability of\nthe will to the feeling of obligation, which varies very considerably\nin individuals.\n\nA scientific study of the moral law, on the basis of physiology,\nevolution, ethnography, and history, teaches us that its precepts\nrest on biological grounds, and have been developed in a natural way.\nThe whole of our modern morality and social and juridical order have\nevolved in the course of the nineteenth century out of the earlier\nand lower conditions which we now generally regard as things of the\npast. The social morality of the eighteenth century proceeded, in its\nturn, from that of the seventeenth and sixteenth centuries, and still\nfurther from that of the Middle Ages, with its despotism, fanaticism,\nInquisition, and witch trials. It is equally clear from modern\nethnography and the comparative psychology of races that the morality\nof barbarous races has been evolved gradually from the lower social\nrules of savage tribes, and that these differ only in degree, not in\nkind, from the instincts of the apes and other social vertebrates. The\ncomparative psychology of the vertebrates shows, further, that the\nsocial instincts of the mammals and birds have arisen from the lower\nstages of the reptiles and amphibia, and these in turn from those\nof the fishes and the lowest vertebrates. Finally, the phylogeny of\nthe vertebrates proves that this highly developed stem has advanced\nthrough a long series of invertebrate ancestors (chordonia, vermalia,\ngastr\u00e6ada) from the protists by a process of gradual modification.\nWe find, even among these unicellulars (first protophyta, then\nprotozoa), the important principle which lies at the base of morality,\nassociation, or the formation of communities. The adaptation of the\nunited cell-individuals to each other and to the common environment is\nthe physiological foundation of the first traces of morality among the\nprotists. All the unicellulars that abandon their isolated eremitic\nlives, and unite to form communities, are compelled to restrict\ntheir natural egoism, and make concessions to altruism in the common\ninterest. Even in the globular c\u0153nobia of volvox and magosph\u00e6ra the\nspecial form and movement and mode of reproduction are determined by\nthe compromise between the egoistic instincts of the individual cells\nand the altruistic need of the community.\n\nMorality, whether we take it in the narrower or broader sense, can\nalways be traced to the physiological function of adaptation, which\nis closely connected through nutrition with the self-maintenance of\nthe organism. The change in the plasm which adaptation brings about is\nalways based on the chemical energy of metabolism (chapter ix.). Hence\nit will be as well to have a clear idea of the nature of adaptation. I\ndefined it as follows in my _General Morphology_:\n\n Adaptation or variation is a general physiological function of\n organisms, closely connected with their radical function of\n nutrition. It expresses itself in the fact that every organism may\n be modified by the influence of the environment, and may acquire\n characters which were wanting in its ancestors. The causes of\n this variability are chiefly found in a material correlation\n between parts of the organism and the outer world. Variability or\n adaptability is not, therefore, a special organic function, but\n depends on the material, physico-chemical process of nutrition.\n\nI have developed this conception of adaptation in the tenth chapter of\nthe _History of Creation_.\n\nThe nature of the adaptation and its relation to variation are often\nconceived in different ways from that I have defined. Quite recently\nLudwig Plate has restricted the idea, and understood by adaptation only\nvariations that are _useful_ to the organism. He severely criticises\nmy broader definition, and calls it \"a palpable error,\" suggesting\nthat I only retain it because I am not open to conviction. If I wanted\nto return this grave charge, I might point to Plate's one-sided and\nperverse treatment of my biogenetic law. Instead of doing this I will\nonly observe that I think the restriction of adaptation to useful\nvariations is untenable and misleading. There are in the life of man\nand of other organisms thousands of habits and instincts that are\nnot useful, but either indifferent or injurious to the organism,\nyet certainly come under the head of adaptation, are maintained by\nheredity, and modify the form. We find adaptations of all sorts--partly\nuseful, partly indifferent, partly injurious (the result of education,\ntraining, distortion, etc.)--in the life of man, and the domestic\nanimals and plants. I need only refer to the influence of fashion\nand the school. Even the origin of the useless (and often injurious)\nrudimentary organs depends on adaptation.\n\nHabit is a second nature, says an old proverb. This is a profound\ntruth, the full appreciation of which came to us through Lamarck's\ntheory of descent. The formation of a habit consists in the frequent\nrepetition of one physiological act, and so is in principle reducible\nto cumulative or functional adaptation. Through this frequent\nrepetition of one and the same act, which is closely connected with the\nmemory of the plasm, a permanent modification is caused, either in a\npositive or a negative sense; _positively_ the organ is developed and\nstrengthened by exercise, _negatively_ it is atrophied or enfeebled\nby disuse. When this accumulation of slight changes continues, the\neffect of adaptation goes so far in time as to produce new organs\nby progressive modification, or to cause actual organs to become\nuseless and rudimentary, and finally disappear, owing to regressive\nmetamorphosis.\n\nWhen we make a careful study of the simpler processes of habit in the\nlower organisms, we see that they depend, like all other adaptations,\non chemical changes in the plasm, and that these are provoked by\ntrophic stimuli--that is to say, by external action on the metabolism.\nAs Ostwald rightly says: \"The most important function of organisms\nis the conversion of the various chemical energies into each other.\nThe chemical energy that is taken into the organism as food is not\ngenerally capable of being applied directly to its purposes, but needs\nsome further preparation. Every cell is a chemical laboratory, in\nwhich the most varied reactions take place without fires and retorts.\nThe most frequently employed means in this is probably the catalytic\nacceleration of the usable and the catalytic retardation of the useless\nreactions. As a proof of this we have the regular presence of these\nenzyma in all organisms.\" In this the greatest importance attaches to\nmemory, which I regard with Hering as a general property of living\nsubstance, \"in virtue of which certain processes in the living being\nleave effects behind them that facilitate the repetition of the\nprocesses.\" I agree with Ostwald that \"the importance of this property\ncannot be exaggerated. In its more general forms it effects adaptation\nand heredity, in its highest development the conscious memory.\" While\nthe latter, and consciousness in general, reach the highest stage in\nthe mental life of civilized man, the adaptation of the monera remains\nat the lowest stage. Among the latter the bacteria especially, which\nhave assumed the most varied and important relations to other organisms\nin spite of the simplicity of their structure, show that this manifold\nadaptation depends on the formation of habits in the plasm, and is\nsolely based on their chemical energy, or their invisible molecular\nstructure. Once more the monera form a connecting link between the\norganic and inorganic; they fill up the deep gulf, from the point of\nview of energy, that seems to yawn between \"animated\" organisms and\n\"lifeless\" bodies.\n\nAccording to the prevailing view, habit is a purely biological process,\nbut there are processes even in inorganic nature which come under this\nhead in the broader sense. Ostwald gives the following illustration:\n\n If we take two equal tubes of thin nitric acid and dissolve a little\n metallic copper in one of them, the liquid will acquire the power to\n dissolve a second piece of the same metal more quickly than the one\n that remains unchanged. The cause of this phenomenon--which may be\n observed in the same way with mercury or silver and nitric acid--is\n that the lower oxydes of nitrogen that are formed in dissolving the\n metal accelerate the action of the nitric acid catalytically on the\n fresh metal. The same effect is produced if you put part of these\n oxydes in the acid; it then acts much more rapidly than pure acid.\n The formation of a habit consists, therefore, in the production of a\n catalytic acceleration during the reaction.\n\nWe may not only compare inorganic habit with organic adaptation, which\nwe call habit or practice, but also with \"imitation,\" which implies a\ncatalytic transfer of habits to socially united living beings.\n\nBy instincts were formerly understood, as a rule, the unconscious\nimpulses of animals which led to purposive actions, and it was\nbelieved that every species of animal had special instincts implanted\nin it by the Creator. Animals were thought, according to Descartes's\nview, to be unconscious machines whose actions proceed with unvarying\nconstancy in the particular form that God had ordained. Although\nthis antiquated theory of instinct is still taught by many dualistic\nmetaphysicians and theologians, it has long since been demolished\nby the monistic theory of evolution. Lamarck had observed that most\ninstincts are formed by habit and adaptation, and then transmitted by\nheredity. Darwin and Romanes especially showed afterwards that these\ninherited habits are subject to the same laws of variation as other\nphysiological functions. However, Weismann has recently taken great\npains in his _Lectures on the Theory of Descent_ (xxiii.) to refute\nthis idea, and in general the hypothesis of an inheritance of acquired\ncharacters, because it will not harmonize with his theory of the\ngerm-plasm. Ernst Heinrich Ziegler, who has recently (1904) published\na subtle analysis of former and present ideas of instinct, agrees with\nWeismann that \"all instincts are due to selection, and that they have\ntheir roots not in the practice of the individual life, but in the\nvariations of the germ.\" But where else can we find the cause of these\n\"germ-variations\" except in the laws of direct and indirect adaptation?\nIn my opinion, it is just the reverse; the remarkable phenomena of\ninstinct yield a mass of evidence of progressive heredity, completely\nin the sense of Lamarck and Darwin.\n\nThe great majority of organisms live social lives, and so are united by\nthe link of common interests. Of all the relations which determine the\nexistence of the species, the chief are those which bind the individual\nto other individuals of the species. This is at once clear from the\nlaws of sexual propagation. Moreover, the association of individuals is\na great advantage in the struggle for existence. In the case of the\nhigher animals this association becomes particularly important, because\nit is accompanied by an extensive division of labor. Then arises the\nantithesis of the personal egoism and the communal altruism; and in\nhuman societies the opposition of the two instincts is all the greater\nwhen reason recognizes that each has a right to satisfaction. Social\nhabits become moral habits, and their laws are afterwards taught as\nsacred duties, and form the basis of the juridical order.\n\nThe morals of nations, so rich in psychological and sociological\ninterest, are nothing more than social instincts, acquired by\nadaptation, and passed on from generation to generation by heredity.\nAn attempt has been made to distinguish between the two kinds of habit\nby describing the instincts of animals as constant vital functions\nbased on their physical organization, and the habits or morals of human\nbeings as mental powers maintained by a spiritual tradition. This\ndistinction has, however, been excluded by the modern physiological\nteaching that men's morals are, like all their other psychic functions,\nbased physiologically on the organization of their brain. The habits\nof the individual man, which have been formed by adaptation to his\npersonal conditions, become hereditary in his family; and these family\nusages can no more be sharply distinguished from the general morals of\nthe community than these can be from the precepts of the Church and the\nlaws of the state.\n\nWhen a certain habit is regarded by all the members of a community\nas important, its cultivation favored and its breach punished, it is\nraised to the position of a duty. This is true even in the case of the\nherds of mammals (apes, gregarious carnivora, and ungulates) and the\nflocks of social birds (hens, geese, ducks). The laws which have been\nformed in these cases by the higher development of social instincts\nare particularly striking and equivalent to those of savage tribes\nwhen conspicuous individuals (old or strong males) have acquired a\nleadership of the troop, and successfully insure the observance of\nthe proper habits or duties. Many of these organized bands are in\nsome respects higher than the savages at the lowest stages who live\nin isolated families, or only form loose temporary associations of a\nfew families. The great progress made by comparative psychology and\nethnology, and historical and prehistorical research, in the second\nhalf of the nineteenth century, confirms us in the conviction that a\nlong scale of intermediate stages joins the rudiments of law in the\nsocial primates and other mammals to the sense of law in the lower\nsavage, and this again to that of the barbarian and the civilized human\nbeing--right up to the science of law in modern Europe.\n\nLike civil laws, the commands of religion come originally from the\nmorals of the savage, and eventually from the social instincts of\nthe primates. The important province of mental life to which we give\nthe vague name of religion was developed at an early stage among the\nprehistoric races from whom we all descend. When we study its origin\nfrom the point of view of empirical psychology and monistic evolution,\nwe find that religion has arisen polyphyletically from different\nsources--ancestor worship, the desire of personal immortality, the\ncraving for a causal explanation of phenomena, superstition of various\nkinds, the strengthening of the moral law by the authority of a divine\nlaw-giver, etc. According as the imagination of the savage or the\nbarbarian followed one or other of these lines it raised up hundreds\nof religious forms. Only a few of them survived in the struggle for\nexistence, and acquired (at least outwardly) dominion over the modern\nmind. But as independent and impartial science advances in our time,\nreligion is purified of superstition and turns more and more to\nmorality.\n\nThe obedience to the \"divine commands\" which religion demands of\nits followers is often transferred by human society to rules that\nhave arisen from social customs of subordinate kinds. Thus we get\nthe familiar confusion of manners and morals, of conventional outer\ndeportment and real inner morality. The ideas of good and bad, morality\nand immorality, are subjected to arbitrary definitions. In this a\ngreat part is played by the moral pressure which is exercised by\nconventional ideas in the social body on the conduct and minds of its\nmembers. However clearly and rationally the individual thinks about the\nimportant questions of practical life, he has to yield to the tyranny\nof traditional and often quite irrational customs. As a matter of fact,\nboth in life and in the nature of the case practical reason does take\nthat precedence of pure reason which Kant claimed.\n\nThe tyranny of custom in practical life does not depend merely on the\nauthority of social usage, but also on the power of selection. Just as\nnatural selection insures the relative constancy of the specific form\nin the origin of the animal and plant species, so it has a powerful\neffect on the origin of morals and customs. An important factor in this\nis mimetic adaptation, or mimicry, the aping or imitating of certain\nforms or fashions by various classes of animals. This is unconscious in\nthe case of many orders of insects, butterflies, beetles, hymenoptera,\netc. When insects of a certain family come to resemble in their outer\nform and color and design those of another family, they obtain the\nprotection or other advantages which these particular characters give\nin the struggle for life. Darwin, Wallace, Weismann, Fritz M\u00fcller,\nBates, and others, have shown in numbers of instances how the origin\nof these deceptive resemblances can be traced to natural selection,\nand how important they are in the formation of the species. But many\ncustoms and usages in human life arise in just the same way, partly by\nconscious and partly by unconscious imitation. Of these the varying\nexternal forms which we call \"fashions\" have a most important influence\nin practical life. The phrase \"fashion-ape,\" when used in a scientific\nsense, is not merely an expression of contempt, but has also a profound\nmeaning; it correctly indicates the origin of fashions by imitation,\nand also the peculiar resemblance we find in this respect between man\nand his cousins, the apes. Sexual selection among the primates has a\ngood deal to do with this.\n\nThe great importance which Darwin ascribes in his _Descent of Man_\nto the \u00e6sthetic selection of the respective sexes is equally true of\nman and of all the higher vertebrates that have a feeling of beauty,\nespecially the amniotes (mammals, birds, and reptiles). The beautiful\ncoloring and marking and ornamentation which distinguish the males from\nthe females are due entirely to the careful individual selection of the\nformer by the latter. Thus the various kinds of ornamental hair (beard,\nhair of head, etc.), the tint of the face, the peculiar form of the\nlips, nose, ears, etc., are to be explained, as we find them in man and\nthe male ape; also the brilliant plumage of the humming-bird, the bird\nof paradise, pheasant, etc. I have dealt fully with these interesting\nfacts in the eleventh chapter of the _History of Creation_, and must\nrefer the reader thereto. I will only point out here how valuable the\nwhole of this chapter of Darwinism is for the understanding of the\nfoundation of species on the one hand and men's fashions and customs on\nthe other. It is most closely connected with ethical problems.\n\nThe growth of fashion in civilized life is very important, not only for\nthe development of the sense of beauty and for the sexual selection\nof the sexes, but also in connection with the origin of the feeling of\nshame and the finer psychological traits that relate to it. The lower\nsavages have no more sense of shame than animals or children. They are\nquite naked, and accomplish the sexual act without the slightest trace\nof shame. The beginning of clothing which we find among the middle\nsavages is not due to a sense of shame, but partly to low temperature\n(in the polar regions), partly to vanity and love of decoration (such\nas ornamenting the ears, lips, nose, and sex-organs by the insertion\nof shells, pieces of wood, flowers, stones, etc.). Afterwards the\nsense of shame sets in, and we have the covering of certain parts of\nthe body with leaves, girdles, shirts, etc. In most nations the sexual\nparts are the first to be covered; though some attach importance to the\nveiling of the face. In many Oriental tribes (especially Mohammedan)\nit is still the first precept of female chastity to veil the face (the\nmost characteristic part of the individual), while the rest of the body\nmay remain naked. Generally speaking, the \u00e6sthetic and psychological\nrelations of the sexes play the chief part in the higher development of\nmorals. Morality is often taken to be synonymous with the law of sexual\nintercourse.\n\nAs the features of civilized life advance, the influence of reason\nincreases, and so does the power of hereditary tradition and the moral\nideas associated with it. The result is a severe conflict between the\ntwo. Reason seeks to judge everything by its own standard, to learn\nthe causes of phenomena and direct practical life accordingly. On\nthe other hand tradition, or \"good morals,\" looks at everything from\nthe point of view of our forefathers and other venerable laws and\nreligious precepts. It is indifferent to the independent discoveries\nof reason and the real causes of things. It demands that the practical\nlife of every individual be framed in accordance with the hereditary\nmorality of the race or state. Thus we get the inevitable conflict\nbetween reason and tradition, or science and religion, which continues\nin our own day. Sometimes in the course of it a \"new fashion\" is\nsubstituted for some sacred tradition, a transitory custom that\nsucceeds in imposing itself by its novelty or curiosity; and when this\nhas contrived to win general acceptance, or has gained the support of\nChurch or state to some extent, it is regarded in much the same light\nas the older morality.\n\nThe lowest races of the present time (for instance, the pithecoid\npygmies, the Veddahs of Ceylon, the Akkas of Central Africa) are very\nlittle higher than their primate ancestors in mental development. This\nis also true of their habits of life and morals. As their ideas are for\nthe most part concrete and sensual, their power of forming abstract\nconcepts is very little developed; they have hardly any religious ideas\nto speak of. But with the middle savages we begin to find the craving\nto know the causes of things and the idea of spirits that are concealed\nbehind the phenomena of sense. Dread of these leads to worship,\nfetichism, and animism, the beginning of religion. Even at this early\nstage of worship we find certain customs associated with the cult to\nwhich a symbolical or mysterious meaning is given. These ceremonies\nlead on in the higher races to the great religious festivities,\nwhich the Greeks called \"mysteries.\" Sensual images of various kinds\nare mixed up in them with supersensual ideas and superstitions. The\nfestivals, processions, dances, hymns, and sacrifices of all sorts that\nform part of the cult are more or less concerned with the mysterious,\nand are therefore considered \"holy.\" They are often made the pretext of\nsensual gratifications, which end in gross immorality and orgies.\n\nFrom the older pagan and Jewish religious usages were afterwards\ndeveloped in the Christian Church those parts of the cult which are\nknown as sacraments. These miraculous sacraments, by the mysterious\naction of which man is supposed to be born again or regenerated, very\nquickly became powerful instruments in the hand of the Church and\nthorny problems for theologians, especially after Gregory the Great\nintroduced the dogmas of Purgatory and the relieving power of the Mass.\nAccording to St. Thomas of Aquin, the sacraments are channels that\nconvey the grace of God to sinful man. The papal authorities fixed\ntheir number at seven (baptism, eucharist, penance, confirmation,\nmatrimony, orders, and extreme unction) in the twelfth century. The\nsuperstitious content of these sacraments was generally lost sight\nof in the glamour of their ceremonious side, but their authority was\nunshaken. Since the Reformation the Protestants have retained only the\ntwo chief sacraments which were founded by Christ himself--Baptism and\nthe Lord's Supper.\n\n Christian baptism is a continuation of the older ceremonies of\n washing and purification that were in use thousands of years before\n Christ among nations of the East and among the Greeks. They combined\n the hygienic value of the bath with the idea of a regeneration of the\n soul and spiritual purification. Augustine, who founded the dogma of\n original sin, held that the baptism of children was necessary for the\n salvation of their souls, and it then became general. It has since\n given rise to a number of superstitious ideas and unfortunate family\n troubles, but it is still regarded as a sacred ceremony. Millions of\n Christians still believe that the child's soul is saved (though it\n has no consciousness whatever when baptized) and delivered from the\n power of the devil and the curse of sin by baptism.\n\n The second sacrament that Luther retained is the Lord's Supper, or\n the sacrament of the body and blood of Christ. It was instituted by\n Christ on the night before his death, and is a continuation of the\n paschal supper of the Jews, in which the head of the house shared\n bread and wine with his family with certain ritual ceremonies. In\n this paschal supper the people of Israel celebrated their release\n from the bondage of Egypt and their distinction as the \"chosen\n people.\" By connecting his \"last supper\" with the traditional\n rite of the Jews, Christ sought on the one hand to found the new\n dispensation on the old, and on the other hand to institute a\n love-feast (communion or agape) among his followers. Like baptism,\n the Lord's Supper led afterwards to the bitterest controversy among\n theologians.\n\n The differences of opinion as to the Eucharist in the Middle Ages\n culminated at last in the opposition of the two reformers, Luther and\n Zwingli. The latter, the founder of the Free Reformed Church, saw\n in the Supper only a symbolical act and a commemoration of Christ.\n Luther, however, adhered to the mysterious miracle that had been\n defined in 1215 by the dogma of transubstantiation. Bread and wine\n are believed on this view to be converted physically into the body\n and blood of Christ! I was taught this in 1848 by the minister who\n prepared me for confirmation, and to whom I was greatly attached. We\n were actually to perceive this change when we assisted at the Supper\n for the first time, if we did so with real faith. As I was quite\n conscious of having this quality, I had great expectations of the\n miracle. But I was very painfully disillusioned when I found only the\n familiar taste of bread and wine, not the flesh and blood that faith\n had desired. I had to regard myself (then a boy of fourteen years) as\n an utterly abandoned sinner, and it was with the greatest difficulty\n that my parents succeeded in pacifying me over my want of faith.\n\n I have spoken somewhat fully in the seventeenth chapter of the\n _Riddle_ of the view of the papacy and ultramontanism which modern\n historical and anthropological science leads us to form. No one\n who has any idea of history and of the metamorphoses of religion\n can question that Romanism is a miserable caricature of primitive\n Christianity; it retains the name, but has completely reversed the\n principles. In the course of its domination, from the fourth to the\n sixteenth century, the papacy has raised up the marvellous structure\n of the Catholic hierarchy, but has departed farther and farther\n from the stand-point of pure Christianity. The aim of Romanism is\n to-day, as it was a thousand years ago, to dominate and exploit a\n blindly believing humanity. It finds admirable instruments for this\n in its mystic sacraments, to which it has ascribed an \"indelible\n character.\" From the cradle to the grave, from baptism to the last\n anointing, in confirmation and penance, the believer must be reminded\n that he must live as an obedient and self-sacrificing child; and the\n sacrament of ordination must teach him that the priest, with his\n higher inspiration, is the only intermediary between man and God. The\n symbolical rites that are associated with these sacraments serve\n to surround them with the magic of the mysterious and exclude the\n penetration of reason. This is particularly true of the sacrament\n that has had the greatest practical influence--matrimony.\n\nIn view of the extreme importance of the life of the family as a\nfoundation of social and civic life, it is advisable to consider\nmarriage from the biological point of view, as an orderly method of\nreproduction. Here, as in all other sociological and psychological\nquestions, we must be careful not to accept the present features of\ncivilized life as a general standard of judgment. We have to take\na comparative view of its various stages, as we find them among\nbarbarians and savages. When we do this impartially, we see at once\nthat reproduction, as a purely physiological process having for its\nend the maintenance of the species, takes place in just the same way\namong uncultivated races as among the anthropoid apes. We may even say\nthat many of the higher animals, especially monogamous mammals and\nbirds, have reached a higher stage than the lower savages; the tender\nrelations of the two sexes towards each other, their common care of\ntheir young, and their family life, have led to the development of\nhigher sexual and domestic instincts, to which we may fitly ascribe a\nmoral character. Wilhelm B\u00f6lsche has shown, in his _Life of Love in\nNature_, how a long series of remarkable customs has been developed\nin the animal world by adaptation to various forms of reproduction.\nWestermarck has pointed out, in his _History of Marriage_, how the\ncrude animal forms of marriage current among savages have been\ngradually elevated as we rise to higher races. As the sensual pleasure\nof generation is combined with the finer psychological feeling of\nsympathy and psychic attachment, the latter gains constantly on the\nformer, and this refined love becomes one of the richest sources of the\nhigher spiritual functions, especially in art and poetry. Marriage\nitself, of course, remains a physiological act, a wonder of life, with\nthe organic sex impulse as its chief foundation. As the conclusion\nof marriage represents one of the most important moments in human\nlife, we find it accompanied by symbolic ceremonies and festive rites\neven among lower tribes. The immense variety of marriage festivals\nshows how this important act has appealed to the imagination. Priests\nquickly recognized this, and decked out marriage with all kinds of\nceremonies and turned it to the advantage of their Church. While the\nCatholic Church raised it to the status of a sacrament and ascribed to\nit an \"indelible\" character, it declared that it was indissoluble when\nperformed according to ecclesiastical rite. This unwholesome influence\nof Romanism, this dependence of matrimony on religious mysteries and\nceremonies, and difficulty of obtaining divorce, etc., still continue\nin our day. It is only a short time since the German Reichstag, under\nthe influence of the Centre [Catholic] party, added laws to its civic\ncode which increase instead of lessening the difficulty of obtaining\ndivorce. Reason demands the liberation of marriage from ecclesiastical\npressure. It demands that matrimony be grounded on mutual love,\nesteem, and devotion, and that it at the same time be counted a social\ncontract, and be protected, as civil marriage, by proper legislation.\nBut when the contracting parties find (as so often happens) that they\nhave mistaken each other's character, and that they do not suit each\nother, they should be free to dissolve the bond. The pressure which\ncomes of marriage being regarded as a sacrament, and which prevents the\ndissolution of unhappy marriages, is merely a source of vice and crime.\n\nWe find in many other features of our social life, besides marriage,\na contradiction between the demands of reason and the traditional\nusages which modern civilization has taken over as a heritage from\nearlier and lower nations, and partly from barbarians and savages. In\nthe public life of states this contradiction is much more striking\nthan in the private life of the family or the individual. Whereas the\nmilder teaching of the Christian religion--sympathy, love of one's\nfellows, patience, and devotion--has had a good influence in many\nways, there can be no question of this in the international relations\nof the nations; here we find pure egoism. Every nation seeks to take\nadvantage of others by cunning or force, and, wherever possible, to\nsubjugate them: if they will not consent, the brute force of war is\nemployed. Social misery of all kinds spreads wider and wider, almost in\nproportion as civilization develops. Alexander Sutherland is right when\nhe characterizes \"the leading nations of Europe and their offshoots\"\n(in the United States) as _lower_ civilized races. In some respects we\nare still barbarians.\n\nHow far the bulk of modern nations still are from the ideal and\nthe reign of pure reason can be seen by a glance at the social,\njuridical, and ecclesiastical condition of \"these leading nations\nof Europe,\" either Teutonic or Latin. We need only consider with an\nunprejudiced mind the accounts in our journals of parliamentary and\nlegal proceedings, government measures and social relations, in order\nto realize that the force of tradition and fashion is immense, and\nresists the claims of reason on every side. This is most clearly seen\nexternally in the power of fashion, especially as regards clothing.\nThere is a good ground for the complaint about \"the tyranny of\nfashion.\" However unpractical, ridiculous, ugly, and costly a new\ngarment may be, it becomes popular if it is patronized by authority,\nor some clever manufacturer succeeds in imposing it by specious\nadvertisements. We need only recall the crinoline of fifty years ago,\nthe bustle of twenty years ago, and the exposure of the breast and\nback by low dresses (with the object of sexual excitement) which was\nthe fashion of forty years ago.[11] For centuries we have had the\npernicious fashion of the corset, an article that is as offensive from\nthe \u00e6sthetic as from the hygienic point of view. Thousands of women are\nsacrificed every year to this pitiful fashion, through disease of the\nliver or lungs; nevertheless, the craze for the hour-glass shape of the\nfemale form continues, and the reform of clothing makes little headway.\nIt is just the same with numbers of fashions in the home and in\nsociety, of devices in commerce and laws in the state. Everywhere the\ndemands of reason advance little in their struggle with the venerable\nusages of tradition.\n\nA false sense of honor dominates our social life, just as a false\nsense of modesty controls our clothing. The true honor of man or woman\nconsists in their inner moral dignity, in the determination to do only\nwhat they conceive to be good and right, not in the outer esteem of\ntheir fellows or in the worthless praise of a conventional society.\nUnfortunately, we have to admit that in this respect we are still\nlargely ruled by the foolish views of a lower civilization, if not of\ncrude barbarians.\n\nIn many other features of our life besides this false modesty and\nfalse honor we perceive the force of social usage. Many of what are\nthought to be honorable customs are relics of barbarism; much of our\nmorality is, in the light of pure reason, downright immorality. As\neven the latter is due to adaptation, and as the same custom may be\nat one time thought useful and fitting, at another time injurious\nand bad, we see again that it is impossible to restrict the idea of\nadaptation to useful variations. We may say the same of the changing\nrules of education, commerce, legislation, and so on. The ideal in all\ndepartments of life is pure reason; but it has to struggle long against\nthe current prejudices and customs, which find their chief support in\nthe superstitions of the Church and the conservative tendencies of the\nstate. In this state of Byzantine immorality, decorating itself so\noften with the mantle of piety, practical materialism flourishes, while\nmonism, or theoretical materialism, is thrust aside.\n\nIf we sum up all that monistic science has taught us as to the origin\nand development of morality, we may put it in the following series\nof propositions: 1. By adaptation to different conditions of life\nthe simple plasm of the earliest organisms, the archigonous monera,\nundergoes certain modifications. 2. As the living plasm reacts on\nthese influences, and the reaction is often repeated, a habit is\nformed (as in the catalysis of certain inorganic chemical processes).\n3. This habit is hereditary, the repeated impressions being fixed\nin the nucleus (or caryoplasm) in the case of the unicellulars. 4.\nWhen hereditary transmission lasts through many generations, and is\nstrengthened by cumulative adaptation, it becomes an instinct. 5. Even\nin the protist c\u0153nobia (the cell-communities of the protophyta and\nprotozoa) social instincts are formed by association of cells. 6.\nThe antithesis of the individual and social instinct, or of egoism\nand altruism, increases in the animal kingdom in proportion to the\ndevelopment of psychic activity and social life. 7. In the higher\nsocial animals definite customs arise in this way, and these become\nrights and duties when obedience to them is demanded by the society\n(herd, flock, people) and the breach of them punished. 8. Savage races\nat the lowest stage, without religion, are not differently related to\ntheir customs than the higher social animals. 9. The higher savages\ndevelop religious ideas, combine their superstitious practices\n(fetichism and animism) with ethical principles, and transform their\nempirical moral laws into religious commands. 10. Among barbaric, and\nmore particularly among civilized, races definite moral laws are formed\nby the association of these hereditary religious, moral, and legal\nideas. 11. In the civilized races the Church formulates the religious\ncommands, and jurisprudence the legal commands, in more definitely\nbinding forms; the advancing mind remains, however, subject in many\nrespects to Church and state. 12. In the higher civilized nations pure\nreason gains more and more influence on practical life, and thrusts\nback the authority of tradition; on the basis of biological knowledge a\nrational or monistic ethic is developed.\n\n\n\n\nXIX\n\nDUALISM\n\n Dualistic systems of Kant I. and Kant II.--His\n antinomies--Cosmological dualism--The two worlds--The world\n of bodies and the world of spirits--Truth and fiction--Goethe\n and Schiller--Realism and idealism--Anti-Kant--Law of\n substance--Attributes of substance--Sensation and energy--Passive\n and active energy--Trinity of substance: matter, force, and\n sensation--Constancy of sensation--Psyche and physics--Reconciliation\n of principles.\n\n\nThe history of philosophy shows how the mind of man has pressed along\nmany paths during the last two thousand years in pursuit of truth.\nBut, however varied are the systems in which its efforts have found\nembodiment, we may, from a general point of view, arrange them all\nin two conflicting series--monism, or the philosophy of unity; and\ndualism, or the philosophy of the duality of existence. Lucretius\nand Spinoza are distinguished and typical representatives of monism;\nPlato and Descartes the great leaders of dualism. But besides the\nconsistent thinkers of each school there are a number of philosophers\nwho vacillate between the two, or who have held both views at different\nperiods of life. Such contradictions represent a personal dualism on\nthe part of the individual thinker. Immanuel Kant is one of the most\nfamous instances of this class; and as his critical philosophy has\nhad a profound influence, and I was compelled to contrast my chief\nconclusions with those of Kant, I must once more deal briefly with his\nideas. This is the more necessary as one of the ablest of the many\nattacks on the _Riddle_, the _Kant against Haeckel_ of Erich Adick, of\nKiel, belongs to this school.\n\nIn the _Creed of Pure Reason_, which I published as an appendix to\nthe popular edition of the _Riddle_ in 1903, I pointed out, in view\nof this and similar Kantist criticisms, the clear inconsistency of\nthe great evolutionary principles of Kant, the natural philosopher,\nwith the mystic teaching which he afterwards made the foundation of\nhis theory of knowledge, and that is still greatly esteemed. Kant I.\nexplained the constitution and the mechanical origin of the universe\non Newtonian principles, and declared that mechanicism alone afforded\na real explanation of phenomena; Kant II. subordinated the mechanical\nprinciple to the teleological, explaining everything as a natural\ndesign. Kant I. convincingly proved that the three central dogmas\nof metaphysics--God, freedom, and immortality--are inacceptable to\npure reason. Kant II. claimed that they are necessary postulates of\npractical reason. This profound opposition of principles runs through\nKant's whole philosophic work from beginning to end, and has never been\nreconciled. I had already shown in the _History of Creation_ that this\ninconsistency has a good deal to do with Kant's position in regard to\nevolution. However, this radical contradiction of Kant's views has\nbeen recognized by all impartial critics. It has lately been urged\nwith great force by Paul R\u00e9e in his _Philosophy_ (1903). We need not,\ntherefore, linger in proving the fact, but may go on to consider the\ncauses of it.\n\nA subtle and comprehensive thinker like Kant was naturally perfectly\nconscious of the existence of this inconsistency of his dualistic\nprinciples. He endeavored to meet it by his theory of antinomies,\ndeclaring that pure reason is bound to land in contradictions when\nit attempts to conceive the whole scheme of things as a connected\ntotality. In every attempt to form a unified and complete view\nof things we encounter these unsolvable antinomies, or mutually\ncontradictory theses, for both of which sound proof is available.\nThus, for instance, physics and chemistry say that matter must consist\nof atoms as its simplest particles; but logic declares that matter\nis divisible _in infinitum_. On the one theory time and space are\ninfinite; on the other theory, finite. Kant attempted to reconcile\nthese contradictions by his transcendental idealism, by the assumption\nthat objects and their connection exist only in our imagination, and\nnot in themselves. In this way he came to frame the false theory of\nknowledge which is honored with the title of \"criticism,\" while as a\nmatter of fact it is only a new form of dogmatism. The antinomies are\nnot explained by it, but thrust aside; nor was there more truth in the\nassertion that equal proof is available for theses and antitheses.\n\nThe famous work of Kant's earlier years, _The General Natural History\nand Theory of the Heavens_ (1755), was purely monistic in its chief\nfeatures. It embodied a fine attempt \"to explain the constitution\nand mechanical origin of the universe on Newtonian principles.\" It\nwas mathematically established forty years afterwards by Laplace in\nhis _Exposition du syst\u00e8me du monde_ (1796). This fearless monistic\nthinker was a consistent atheist, and told Napoleon I. that there was\nno room for \"God\" in his _M\u00e9canique celeste_ (1799). Kant, however,\nafterwards found that, though there was no rational evidence of the\nexistence of God, we must admit it on moral grounds. He said the same\nof the immortality of the soul and the freedom of the will. He then\nconstructed a special \"intelligible world\" to receive these three\nobjects of faith; he declared that the moral sense compelled us to\nbelieve in a supersensual world, although pure theoretical reason\nis quite unable to form any distinct idea of it. The categorical\nimperative was supposed to determine our moral sense and the\ndistinction between good and evil. In the further progress of his\nethical metaphysics Kant expressly urged that practical reason should\ntake precedence of theoretical--in other words, that faith is superior\nto knowledge. In this way he enabled theology and irrational faith\nto find a place in his system and claim supremacy over all rational\nknowledge of nature.\n\nThe older Greek philosophy had been purely monistic, Anaximander and\nhis disciple Anaximenes (in the sixth century B.C.) conceiving the\nworld in the sense of our modern hylozoism, but Plato introduced (two\nhundred years afterwards) the dualistic view of things. The world of\nbodies is real, accessible to our sensible experience, changeable and\ntransitory; opposed to it is the world of spirits, only to be reached\nby thought, supersensual, ideal, immutable, and eternal. Material\nthings, the objects of physics, are only transient symbols of the\neternal ideas, which are the subject of metaphysics. Man, the most\nperfect of all things, belongs to both worlds; his material frame is\nmortal, the prison of the immortal and invisible soul. The eternal\nideas are only embodied for a time in the world of bodies here below;\nthey dwell eternally in the world of spirits beyond, where the supreme\nidea (God, or the idea of the good) controls all in perfect unity.\nThe human soul, endowed with free-will, is bound to develop the three\ncardinal virtues (wisdom, fortitude, and prudence) by the cultivation\nof its three chief moral faculties (thought, courage, and zeal). These\nfundamental principles of Plato's teaching, systematically presented\nby his pupil Aristotle, met with a very general acceptance, as they\ncould easily be combined with the teaching of Christianity which arose\nfour hundred years afterwards. The great majority of later philosophic\nand religious systems followed the same dualistic paths. Even Kant's\nmetaphysics is only a new form of it; only its dogmatic character\nis hidden by the ascription to it of the convenient title of the\n\"critical\" system.\n\nModern science has opened out to us immense departments of the real\nworld that are accessible to observation and rational inquiry; but it\nhas not taught us a single fact that points to the existence of an\nimmaterial world. On the contrary, it has shown more and more clearly\nthat the supposed world beyond is a pure fiction, and only merits to be\ntreated as a subject for poetry. Physics and chemistry in particular\nhave proved that all phenomena that come under our observation depend\non physical and chemical laws, and that all can be traced to the\ncomprehensive and unified law of substance. Anthropogeny has taught us\nthe evolution of man from animal ancestors. Comparative anatomy and\nphysiology have shown that his mind is a function of the brain, and his\nwill not free; and that his soul, absolutely bound up with its material\norgan, passes away at death like the souls of other mammals. Finally,\nmodern cosmology and cosmogony have found no trace whatever of the\nexistence and activity of a personal and extramundane God. All that\ncomes within the range of our knowledge is a part of the material world.\n\nIn his observations on the supersensual world Kant lays stress on the\nfact that it lies beyond the range of experience, and is known only by\nfaith. Conscience, he thinks, assures us of its existence, but does\nnot give us any idea of its nature; and so the three central mysteries\nof metaphysics are mere words without meaning. But, as nothing can\nbe done with mere words, Kant's followers have attempted to put a\npositive substance into them, generally in relation to traditional\nideas and religious dogmas. Not only orthodox Kantians, but even\ncritical philosophers like Schleiden, have dogmatically asserted that\nKant and his disciples have established the transcendental ideas of\nGod, freedom, and immortality, just as Kepler, Newton, and Laplace\nestablished the laws of celestial motion. Schleiden imagined that this\ndogmatic affirmation would refute \"the materialism of modern German\nscience.\" Lange has shown, on the contrary, that such dogmatism is\nutterly foreign to the spirit of the _Critique of Pure Reason_, and\nthat Kant held the three ideas to be quite incapable of either positive\nor negative proof, and so thrust them into the domain of practical\nphilosophy. Lange says: \"Kant would not see, as Plato would not see\nbefore him, that the intelligible world is a world of poetry, and has\nno value except in this respect.\" But if these ideas are mere figments\nof the poetic imagination, if we can form neither positive nor negative\nidea of them, we may well ask: What has this imaginary spirit-world to\ndo with the pursuit of truth?\n\nAs I have raised the question of the limits of truth and fiction, I\nmay take the opportunity of pointing out the general importance of\nthis distinction. Undoubtedly man's knowledge is limited, from the\nvery nature of our faculties or the organization of our brain and\nsense-organs. Hence, Kant is right when he says that we perceive only\nthe phenomena of things, and not their inner essence, which he calls\nthe \"thing in itself.\" But he is wrong and altogether misleading\nwhen he goes on to doubt the reality of the external world, and says\nit exists only in our presentations--in other words, that life is a\ndream. It does not follow, from the fact that our senses and phronema\ncan reach only a part of the properties of things, that we call into\nquestion their existence in time and space. But our rational craving\nfor a knowledge of causes impels us to fill up the gaps in our\nempirical knowledge by our imagination, and thus form an approximate\nidea of the whole. This work of the imagination may be called\n\"fiction\" in a broad sense--hypotheses when they are in science, faith\nwhen they belong to religion. However, these imaginative constructions\nmust always take a concrete form. As a fact, the imagination that\nconstructs the ideal world is never content merely to assume its\nexistence, but always proceeds to form an image of it. But these forms\nof faith have no theoretical value for philosophy if they contradict\nscientific truth, or profess to be more than provisional hypotheses;\notherwise they may be of practical service, but are theoretically\nuseless. Hence we fully recognize the great ethical and pedagogical\nvalue of poetry and myths, but are by no means disposed to give them\nprecedence of empirical knowledge in our quest of the truth. I agree\nentirely with the excellent criticism of Kant which Albert Lange gives\nin his _History of Materialism_ (vol. ii.); but I am unable to follow\nhim when he transfers his idealism from practical to theoretical\nquestions, and urges the erroneous theory of knowledge derived from it\nin opposition to monism and realism. It is true that, as Lange says:\n\n Kant did not lack the sense for the conception of this intelligible\n world (as an imaginative world); but his whole education and the\n period in which his mental life developed prevented him from\n indulging it. As he was denied the liberty of giving a noble form,\n free from all medi\u00e6val distortion, to the vast structure of his\n ideas, his positive philosophy was never fully developed. His system,\n with its Janus face, stands at the limit of two ages. He himself,\n in spite of all the defects of his deductions, is a teacher of the\n ideal. Schiller especially has grasped with prophetic insight the\n very essence of his teaching, and purified it of its scholastic\n dross. Kant held that we must only think, not see, the intelligible\n world; though what he thinks must have objective reality. Schiller\n has rightly brought the intelligible world visibly before us by\n treating it as a poet, and thus following in the footsteps of Plato,\n who, in contradiction to his own dialectic, reached his highest\n thought when he allowed the supersensual to become a thing of sense\n in the myth. Schiller, the poet of freedom, dared to carry freedom\n openly into the land of dreams and of shadows; then there arose under\n his hand the dreams and shadows of the ideal.\n\nIn view of the great influence that Schiller's idealism has had in\nthe spread of Kant's practical moral philosophy, we may for a moment\nconsider it in contrast with the realistic views of Goethe.\n\nThe profound opposition of the views of the two greatest poets of\nthe classical period of German literature is rooted deep in their\nnatures. This has been proved so often and so thoroughly, and has so\nfrequently been represented as the complementary quality of the two\npoets, that I need merely recall it here. As for Goethe, I have, in my\n_General Morphology_, shown his historical importance in connection\nwith the theory of evolution and the system of monism. With all his\nversatile occupations, this great genius found time to devote to the\nmorphological study of organisms, and to establish his comprehensive\nbiological theories on this empirical basis. His discovery of the\nmetamorphosis of plants and his vertebral theory of the skull justify\nus in classifying him as one of the chief forerunners of Darwin.\nWhen I dealt with this in the fourth chapter of the _History of\nCreation_, I pointed out how great an influence these morphological\nstudies, together with his idea of evolution, had on the realism of\nhis philosophy. They led him direct to monism and to an admiration of\nSpinoza's monistic pantheism. Schiller had neither great interest nor\nclear insight for these studies. His idealistic philosophy disposed\nhim rather to Kant's dualistic metaphysics and to an acceptance of\nthe three central mysteries--God, soul, and freedom. Both Schiller\nand Goethe had a thorough knowledge of anthropology and psychology.\nBut the anatomic and physiological studies that Schiller made as a\nmilitary surgeon had very little influence on his transcendental\nidealism, in which the ethical-\u00e6sthetic element preponderated. On the\nother hand, Goethe's empirical realism was profoundly influenced by his\nmedical studies at Strasburg, and especially by his later comparative\nanatomical and botanical investigations at Jena and Weimar.\n\nThe philosophic antithesis which we thus find in the biological\nfoundations of the views of Goethe and Schiller represents to an extent\nthe Janus face that the philosophic genius of the German people bears\nto our own day. Goethe, the realist, penetrated deep into the empirical\nstudy of the material world, and sought, with Spinoza, to establish\nthe unity of the universe. Schiller, the idealist, lives rather\nin the spirit-world, and seeks, with Kant, to utilize its ethical\nideals--God, freedom, and immortality--for the education of the human\nrace. Both tendencies of thought have led the genius of Germany--like\nthe genius of Greece, two thousand years ago--to a great number of vast\nintellectual achievements. Goethe wrought the ideal in his practical\nlife, Kant discovered it, Schiller proclaimed it to be the fittest aim\nof the future.\n\nIt is wrong to conclude from isolated quotations from Goethe that he\noccasionally betrayed the dualism of Schiller in his opinions. Some\nof the remarks in this connection that Eckermann has left us from his\nconversations with Goethe must be taken very carefully. Generally\nspeaking, this source is not reliable; many of the observations that\nthe mediocre Eckermann puts into the mouth of the great Goethe are\nquite inconsistent with his character, and are more or less perverted.\nHence, when recent high-placed orators declare at Berlin that Goethe\nsaved the high ideals of God, freedom, and immortality, like Schiller,\nand thus borrow a certain support for their Christian belief, they only\nshow how little they have grasped the profound antithesis of the views\nof the two poets. Goethe notoriously described himself as a \"renegade\nnon-Christian.\" The creed of the \"great heathen\" Goethe, as we find\nit in _Faust_ and _Prometheus_ and _God and the World_, and a hundred\nother magnificent poems, is pure monism, of the pantheistic character\nwhich we take to be alone correct--hylozoism; he is equally far from\nthe one-sided materialism of Holbach or Carl Vogt and the extreme\ndynamism of Leibnitz and Ostwald. Schiller by no means shared this\nrealistic view of things; his idealistic sense fled beyond nature into\nthe spirit world. However, our theoretic hylozoism does not exclude\npractical idealism, as Goethe's whole life showed. On the other hand,\nprinces and priests often let us see how easily theoretical idealism\ngoes with practical materialism, or hedonism.\n\nIn the month of February, 1904, the centenary of the death of Kant was\ncelebrated throughout the world of culture. In numbers of academic\nspeeches and writings he was greeted as the greatest thinker of\nGermany. He died on the same date (February 12th) on which Darwin\nwas born five years later. It is unquestionable that Kant has had\nan immense influence on the whole development of German philosophy.\nBut while recognizing his extraordinary genius, we must not be blind\nto the glaring contradictions and defects of his dualist system.\nFrom the monistic point of view, we can only regard his profound\ninfluence during the whole of the nineteenth century as mischievous.\nMost certainly he had a quite exceptional talent for philosophic\nspeculation and penetrating thought, and he added to his great mental\nqualities a blameless character and an undeniable sense of truth in\nlife (though not in thought). It was a serious misfortune for Kant and\nfor the philosophic school he led that his education prevented him\nfrom acquiring a thorough knowledge and correct conception of the real\nworld. Shut up throughout life within the narrow bounds of his native\ntown, K\u00f6nigsberg, he never travelled beyond the frontier of Prussia,\nand so did not obtain that knowledge of the world that comes of\ntravelling. In the study of nature he confined himself to the physics\nof the inorganic world, in the study of man to the immortal soul. At\nthe close of his university studies Kant had to earn his living as a\nhouse-teacher for nine years (from twenty-two to thirty-one), just\nat the most important period of his life, in which the independent\ndevelopment of the personal and scientific character is decided when\nthe academic studies are over.\n\nIn such adverse circumstances of mental adaptation a deep mystic trait,\nwhich had been inherited from pious parents and confirmed by the\nstrictly religious training of his early years, was fixed in Kant's\ncharacter. Hence it was that faith in the three central mysteries came\nupon him more and more in later years: he gave them precedence over all\nthe attainments of theoretical reason, while granting that we can form\nneither a negative nor positive idea of them. But how can the belief\nin God, freedom, and immortality determine one's whole view of life as\na postulate of practical reason if we cannot form any definite idea of\nthem?\n\nEvery philosophy that deserves the name must have clear ideas as\nthe bases of its thought-structure; it must have definite views in\nconnection with its fundamental conceptions. Hence most of Kant's\nfollowers have not been content to follow his direction merely\nto _believe_ in the three central mysteries; they have sought to\nassociate definite mental pictures with the empty concepts of God,\nfreedom, and immortality. In this they have drawn upon the religious\nimagination, and have passed from the real knowledge of nature into the\ntranscendental realm of poetry. Monism, based on this real knowledge of\nnature, has to keep clear of such dualism.\n\nThe extraordinary glorification of Kant that took place on the occasion\nof his centenary must have seemed strange to many scientists who\nrecognize in his idealism one of the greatest hinderances to the spread\nof the modern monistic philosophy of nature. But it is not difficult to\nexplain this. We must remember, in the first place, the contradictory\nviews that are embodied in Kant's system; every one could find in\nKant's works something to correspond to his own convictions--the\nmonistic physicist could read of the mechanical sway of natural law\nthroughout the whole knowable world, and the dualistic metaphysician of\nthe free play of the divine aim in the spiritual world. The physician\nand physiologist would note with satisfaction that in his criticism of\npure reason Kant had been unable to find any evidence for the existence\nof God, the immortality of the soul, or the freedom of the will. The\njurist and theologian would find with equal gratification that in the\npractical reason Kant claims these three central dogmas as necessary\npostulates. I have shown to some extent, in the sixth chapter of the\n_Riddle_, how these irreconcilable contradictions in Kant's system are\ndue to a psychological metamorphosis.\n\nIt is just these very contradictions, which run through Kant's\nphilosophy from beginning to end, that maintain its popularity.\nEducated people who desire to form a view of life rarely read Kant's\ndifficult (and often obscure) works in the original, but are content\nto learn from extracts, or from a history of philosophy, that the\nK\u00f6nigsberg thinker succeeded in squaring the circle, or in reconciling\nnatural science with the three central dogmas of metaphysics. The\n\"higher powers,\" who are particularly concerned to save the latter,\nfavor the teaching of Kant's dogmas, because it closes the way to real\nexplanation and prevents independent thinking. This is especially\ntrue of the ministers of public instruction in the two chief German\nstates--Prussia and Bavaria. In their open attempt to subordinate the\nschool to the Church, they desire, above all, the primacy of practical\nreason--that is to say, the subjection of pure reason to faith and\nrevelation. In German universities to-day belief in Kant is a sort of\nticket of admission to the study of philosophy. The reader who would\nrealize the pernicious effect of this official faith in Kant on the\nadvance of scientific knowledge will do well to read the able criticism\nin the brilliant posthumous work of Paul R\u00e9e.\n\nIn the face of the dualism which still prevails in the academic\nteaching of philosophy (especially in Germany) we must base our\nmonistic system on the universality of the law of substance. This\nharmoniously combines the laws of the conservation of matter and of\nenergy. As I have fully explained my own conception of this law in\nthe twelfth chapter of the _Riddle_, I will only say here that its\nvalidity is quite independent of any particular theory of the relations\nof matter and force.[12] The materialism of Holbach and B\u00fcchner lays a\none-sided stress on the importance of matter: the dynamism of Leibnitz\nand Ostwald on that of force. If we avoid these extremes, and conceive\nmatter and force as inseparable attributes of substance, we have pure\nmonism, as we find it in the systems of Spinoza and Goethe. We might\nthen substitute for the word \"substance\" as Hermann Cr\u00f6ll does, the\nterm \"force-matter.\" The further question as to the correctness of any\nparticular physical conception of matter is quite independent of this.\n\nThe two knowable attributes or inalienable properties of substance,\nwithout which it is unthinkable, were described by Spinoza as extension\nand thought; we speak of them as matter and force. The \"extended\" (or\nspace-occupying) is matter; and in Spinoza \"thought\" does not mean a\nparticular function of the human brain, but energy in the broadest\nsense. While hylozoistic monism conceives the human soul in this\nsense as a special form of energy, the current dualism or vitalism\naffirms, on the authority of Kant, that psychic and physical forces\nare essentially different; that the former belong to the immaterial\nand the latter to the material world. The theory of psycho-physical\nparallelism, as developed especially by Wundt (1892), gives a very\nsharp and definite expression to this dualism; it says that \"physical\nprocesses correspond to every psychic phenomenon, but the two are\ncompletely independent of each other and have no natural causal\nconnection.\"\n\nThis wide-spread dualism finds its chief support in the difficulty of\ndirectly connecting the processes of sensation with those of movement;\nand so the one is regarded as a psychic and the other as a physical\nform of energy. The conversion of the outer stimulus (waves of light,\nsound, etc.) into an inner sensation (sight or hearing) is regarded\nby monistic physiology as a conversion of force, a transformation of\nphotic or acoustic energy into specific nerve-energy. The important\ntheory of the specific energy of the sensory nerves, as formulated by\nJohannes M\u00fcller, forms a bridge between the two worlds. But the idea\nwhich these sensations evoke, the central process in the thought-organ\nor phronema that brings the impressions into consciousness, is\ngenerally regarded as an incomprehensible mystery. However, I have\nendeavored to prove, in the tenth chapter of the _Riddle_, that\nconsciousness itself is only a special form of nervous energy, and\nOstwald has lately developed the theory in his _Natural Philosophy_.\n\nThe processes of movement which we observe in every change of one form\nof energy into another, or every passage of potential into actual\nenergy, are subordinate to the general laws of mechanics. The dualist\nmetaphysic has rightly said that the mechanical philosophy does not\ndiscover the inner causes of these movements. It would seek these in\npsychic forces. On our monistic principles they are not immaterial\nforces, but based on the general sensation of substance, which we\ncall _psychoma_, and add to energy and matter as a third attribute of\nsubstance.\n\nThe difficulty of combining our monism with Spinoza's doctrine of\nsubstance is met by detaching the idea of energy from sensation and\nrestricting it to mechanics, so as to make movement a third fundamental\nproperty of substance with matter (the \"extended\") and sensation (the\n\"thinking\"). We may also divide energy into active (= will in the sense\nof Schopenhauer) and passive (= sensation in the broadest sense). As a\nmatter of fact, the energy to which modern energism would reduce all\nphenomena has not an independent place in Spinoza's system besides\nsensation; the attribute of thought (the psyche, soul, force) comprises\nthe two. I am convinced that sensation is, like movement, found in\nall matter, and this trinity of substance provides the safest basis\nfor modern monism. I may formulate it in three propositions: (1) No\nmatter without force and without sensation. (2) No force without matter\nand without sensation. (3) No sensation without matter and without\nforce. These three fundamental attributes are found inseparably united\nthroughout the whole universe, in every atom and every molecule. In\nview of the great importance of this view for our hylonistic system of\nmonism, it may be well to consider each of these three attributes in\nconnection with the law of substance.\n\n_A._ MATTER.--As extended substance, matter occupies infinite space,\nand each individual body forms a part of the universe as real\nsubstance. The law of the conservation of matter teaches us that the\nsum of matter is eternal and unchangeable. This applies equally to\nthe various kinds of matter which we call the chemical elements, or\nponderable matter, and to the ether that fills the spaces between\nthe atoms and molecules, or imponderable matter. The mischievous\ndepreciation of matter (and the consequent disdain of materialism) and\nits antithesis to \"spirit\" is partly due to the use of such phrases as\n\"raw\" and \"dead\" matter, and partly to the deep-rooted mysticism we\nhave inherited from barbaric ancestors, and find it hard to shake off.\n\n_B._ ENERGY.--All parts of the substance that fills infinite space\nare in constant and eternal motion. Every chemical process and every\nphysical phenomenon is accompanied by a change in the position of the\nparticles which compose the matter. The law of the conservation of\nenergy teaches us that the sum of force or energy that is ever at work\nin the universe is unchangeable. In the formation or decomposition of a\nchemical compound the particles of matter move about, and so in every\nmechanical, thermic, electric, and other process. The changes that\ntake place depend on a constant change of force, both in organic and\ninorganic bodies; one form of force is converted into another without\na particle of the whole being lost. This law of the conservation of\nforce has lately been called, as a rule, the conservation of energy (or\nthe principle of energy) since the ideas of force and energy have been\nmore clearly distinguished in physics; energy is now usually defined as\nthe product of force and direction. It must be noted, however, that\nthe word \"energy\" (as an equivalent to \"work\" in the physical sense)\nis still used in many different senses, as is also the word \"force.\"\nOthers define energy as \"work or all that comes of work and may be\nconverted into work.\" One particular school of voluntarism (Wundt)\nreduces the motive-force of energy to will. Crusius said in 1744: \"Will\nis the dominating force in the world.\" And Schopenhauer defines the\nworld (or substance) as \"will and presentation.\"\n\n_C._ SENSATION.--In describing sensation (in the broadest sense) as\na third attribute of substance, and separating \"sensitive substance\"\nfrom energy as \"moving substance,\" I rely on the observations I made in\nthe thirteenth chapter of the _Riddle_ on sensation in the organic and\ninorganic world. I cannot imagine the simplest chemical and physical\nprocess without attributing the movements of the material particles to\nunconscious sensation. In this sense the chemist speaks every day of a\nsensitive reaction, and the photographer of a sensitive plate. The idea\nof chemical affinity consists in the fact that the various chemical\nelements perceive the qualitative differences in other elements,\nexperience \"pleasure\" or \"revulsion\" at contact with them, and execute\ntheir specific movements on this ground. The sensitiveness of the plasm\nto all kinds of stimuli, which is called \"soul\" in the higher animals,\nis only a superior degree of the general irritability of substance.\nEmpedocles and the panpsychists spoke in the same sense of sensation\nand effort in all things. As N\u00e4geli said: \"If the molecules possess\nsomething that is related, however distantly, to sensation, it must\nbe comfortable to be able to follow their attractions and repulsions;\nuncomfortable when they are forced to do otherwise. Thus we get a\ncommon spiritual bond in all material phenomena. The mind of man is\nonly the highest development of the spiritual processes that animate\nthe whole of nature.\" These views of the distinguished botanist fully\nagree with my monistic principles.\n\nWhen sensation in the widest sense (as _psychoma_) is joined to matter\nand energy as a third attribute of substance, we must extend the\nuniversal law of the permanence of substance to all three aspects of\nit. From this we conclude that the quantity of sensation in the entire\nuniverse is also eternal and unchangeable, and that every change of\nsensation means only the conversion of one form of psychoma into other\nforms. If we start from our own immediate sensations and thoughts, and\nlook out on the whole mental life of humanity, we see through all its\ncontinuous development the constancy of the psychoma, which has its\nroots in the sensations of each individual. This highest achievement\nof the work of the plasm in the human brain was, however, first\ndeveloped in the sensations of the lower animals, and these are in turn\nconnected by a long series of evolutionary stages with the simpler\nforms of sensation that we find in the inorganic elements, and that\nreveal themselves in chemical affinity. Albrecht Rau expressly says\nin his excellent _Sensation and Thought_ (1896) that \"perception or\nsensation is a universal process in nature. This involves, moreover,\nthe possibility of reducing thought itself to this universal process.\"\nRecently Ernst Mach has said, in his _Analysis of Sensation and the\nRelation of the Physical to the Psychical_, that \"sensations are the\ncommon elements of all possible physical and psychic occurrences, and\nconsist simply in the different mode of the combination of the elements\nand their dependence on each other.\" It is true that Mach, in his\none-sided emphasis of the subjective element of sensation, goes on to\nform a similar psychomonism to that of Verworn, Avenarius, and other\nrecent dynamists; but the fundamental character of his system is purely\nmonistic, like the energism of Ostwald.\n\nIn thus uniting sensation with force and matter as an attribute of\nsubstance, we form a monistic trinity, and are in a position to do away\nwith the antitheses that are rigidly maintained by dualists between the\npsychic and the physical, or the material and the immaterial world.\nOf the three great monistic systems materialism lays too narrow a\nstress on the attribute of matter, and would trace all the phenomena\nof the universe to the mechanics of the atoms or to the movements of\ntheir ultimate particles. Spiritualism, with equal narrowness, builds\non the attribute of energy; it would either explain all phenomena by\nmotor forces or forms of energy (energism), or reduce them to psychic\nfunctions, to sensation or psychic action (panpsychism). Our system of\nhylonism (or hylozoism) avoids the faults of both extremes, and affirms\nthe identity of the psyche and the physis in the sense of Spinoza and\nGoethe. It meets the difficulties of the older theory of identity by\ndividing the attribute of thought (or energy) into two co-ordinate\nattributes, sensation (psychoma) and movement (mechanics).\n\n\n\n\nXX\n\nMONISM\n\n Defence of monism--Pure and applied science (theoretic and\n practical reason)--Pure (theoretical) sciences: physics,\n chemistry, mathematics, astronomy, geology; biology, anthropology,\n psychology, philology, history--Applied (practical) sciences:\n medicine, psychiatry, hygiene, technology, pedagogics, ethics,\n sociology, politics, jurisprudence, theology--Antinomy of the\n sciences--Rational and dogmatic disciplines--Correlation of the\n sciences--Faculties--Reform of education--The ideal world--Harmony of\n monism.\n\n\nNow that we have reached the end of our long journey, we may take a\ngeneral survey of the path we have pursued, and say how far we owe our\nprogress to the monistic philosophy. In doing so, we shall at once\njustify our own point of view and indicate the relation of biology to\nthe other sciences. I feel the more bound to do this as the present\nvolume is not only a necessary supplement to the _Riddle_, but at the\nsame time my last philosophic work. At the end of my seventieth year I\nwould supply some of the defects of the _Riddle_, answer some of the\nmost stringent criticisms directed against it, and as far as possible\ncomplete the philosophy of life at which I worked for half a century.\n\nIn inviting my readers to accompany me once more through the broad\ndomain of the monistic philosophy I must, as their modest guide, show\nscientific justification at the narrow entrance--produce, so to say,\nthe ticket of admission to this investigation. The academic philosophy\nwhich still controls the German universities watches every door with\njealous eyes, and has an especial concern to keep out modern biology.\nOfficial German philosophy is still for the most part taken up with\na medi\u00e6val metaphysic and the dualism of Kant, the openly dogmatic\ncharacter of which it greets as \"criticism.\" In the course of the forty\nyears during which I have taught as ordinary professor of zoology at\nJena I have had occasion to assist at several hundred examinations of\ndoctors, teachers, etc., in which distinguished representatives of\nphilosophy were examiners. I saw that nearly always the chief stress\nwas laid on a kind of conceptual gymnastics and self-observation, and\non the correct knowledge of the innumerable errors which the (mainly\ndualistic) leaders of ancient and modern philosophy have left us in\ntheir vast literature. The central feature of the whole scheme is\nKant's theory of knowledge, the defects and one-sidedness of which I\nhave treated in the first and nineteenth chapters. In psychology a most\nextensive knowledge of psychic powers on the basis of the introspective\nmethod is demanded; the physiological analysis of the \"soul\" and the\nanatomic study of the phronema are carefully avoided, as are also the\ncomparative and genetic study of the mind. Many of our metaphysicians\ngo even farther and regard philosophy as a separate science--a sublime\n\"mental science,\" quite independent of the common empirical sciences.\nOne is tempted to quote the saying of Schopenhauer: \"It is a sure\nsign of a philosopher that he is not a professor of philosophy.\" In\nmy opinion, every educated and thoughtful man who strives to form a\ndefinite view of life is a philosopher. As queen of the sciences,\nphilosophy has the great task of combining the general results of the\nother sciences, and of bringing their rays of light to a focus as in\na concave mirror. The various tendencies of thought that arise in\nsuch numbers have all a right to scientific respect and discussion,\nthe monistic minority no less than the dualistic majority. We have to\ninquire, then, how far monism has succeeded in gaining firm foothold\nin the various fields of science, and we may begin with a distinction\nbetween pure (theoretical) and applied (practical) science.\n\nPure philosophy aims at a knowledge of the truth by means of pure\nreason, as I explained in the first chapter. However, this theoretical\nphilosophy finds itself in most of the sciences in direct and\nfrequently important relations to practical life, and so in the form\nof applied philosophy becomes a weighty factor in civilization. In\nthis the real claims of practical life are often in contradiction to\nthe ideal tenets of the scientifically grounded theory. In such cases,\nin my opinion, the pure pursuit of the truth must take precedence of\napplied philosophy. I thus dissent entirely from the view of Kant,\nwho expressly gives precedence to practical reason, and subordinates\ntheoretical reason to it. Kant's error was fated to have a terrible\ninfluence, because the dominant authorities in Church and state eagerly\nembraced it to insure everywhere the supremacy of the dogmas of\npractical reason over the attainments of pure critical reason.\n\nFrom the point of view of natural monism we may take physics in the\nwider sense as the fundamental science. The term _physis_ (the Greek\nequivalent of the Latin \"nature\"), in its original meaning, comprises\nthe whole knowable world--Kant's _mundus sensibilis_. His supersensual\nor \"intelligible\" world is, on his own definition, the object of\nfaith, not knowledge. It is very remarkable to find a thinker like\nKant contradicting himself already in his fundamental distinction\nof the two worlds. How can the supersensual world, with its three\ncentral mysteries (God, freedom, and immortality), be described as\nintelligible (_i.e._, knowable) when it is proved by pure reason that\nthe human mind is incapable of knowing it, or of forming any positive\nor negative idea of it? _Lucus a non lucendo!_ We may, therefore, leave\nthis supernatural metaphysical world to faith and fiction, and confine\nour studies to the real physical world, nature. The idea of physics\nas a comprehensive natural philosophy, as it was conceived in classic\nGreece, has been more and more restricted in the course of time. To-day\nit is generally taken to mean the science of the phenomena of inorganic\nnature, their empirical determination by observation and experiment\n(experimental physics), and their reduction to fixed natural laws and\nmathematical formul\u00e6 (theoretical or mathematical physics). Of late a\ndistinction has been drawn between the physics of mass and the physics\nof ether; the one deals with mechanics, the movement and equilibrium\nof ponderable matter, of solid, fluid, and gaseous bodies (statics and\ndynamics, gravitation, acoustics, meteorology); the other is occupied\nwith the phenomena of ether (or imponderable matter) and its relations\nto mass (electricity, galvanism, magnetism, optics, and calorics).\nIn all these branches of inorganic physics the monistic view is now\ngenerally received, and all attempt at dualistic explanation abandoned.\n\nThe vast department of chemistry, which has now become so important\nboth for theoretical and practical purposes, is really only a part of\nphysics. But while modern physics restricts itself to the study of\ninorganic forms of energy and their conversions, chemistry, as the\nscience of matter, takes up the study of the qualitative differences\nbetween the various kinds of ponderable matter. It divides ponderable\nbodies into some seventy-eight elements, the relations of which to each\nother have been determined in the periodic system of the elements, and\ntheir probable common origin from some primitive matter (prothyl)\nbeen shown. The constant features of chemical combinations which have\nbeen established by the analysis and synthesis of the elements, and\nespecially the law of simple and multiple proportions discovered in\n1808, led to the empirical determination of the atomic weight of the\nelements and to the chemical theory of the atom. The acceptance of\nthese atoms (as space-filling separate particles of matter--however\nwe may regard them in other respects) is an indispensable hypothesis\nin chemistry, like the hypothesis of the molecule in physics. Modern\ndynamism (or energism) is wrong when it thinks it can dispense with\nthese hypotheses and replace the atoms by the notion of immaterial\nnon-spatial points of force. However, in both the dynamic and the\nmaterial school monism is retained in every department of chemistry.\n\nModern science considers the ultimate aim of all research to be\nthe exact determination of phenomena in measure and number, or the\nreduction of all general knowledge to mathematically formulated laws.\nAs the great Laplace established his system mathematically, it has\nlately been claimed that a comprehensive (ideal) Laplace-mind could\nembrace the whole past, present, and future of the universe in a single\ngigantic mathematical formula. Kant has expressed this exaggerated\nestimate of mathematics in the phrase: \"Every science is only true\nscience in proportion as it is amenable to mathematical treatment\";\nand to this he has added the second error that the mathematical axioms\n(being necessary and universal truths) belong to the _a priori_\nconstitution of the mind, and are independent of experience (_a\nposteriori_). However, John Stuart Mill and others have shown that\nthe fundamental ideas of mathematics are acquired originally, like\nthose of any other science, by abstraction from experience; and the\nmodern phylogeny of the mind has confirmed this empirical view. We\nmust remember, moreover, that mathematics deals only with quantitative\nrelations in time and space, and not with the qualitative features of\nbodies. In fact, Kant himself showed that mathematics only answers for\nthe absolute _formal_ correctness of conclusions it draws from given\npremises, and has no influence on the premises themselves. Hence,\nwhen we examine the abstract thinking-power of the phronema in its\nmathematical operations physiologically and phylogenetically, we find\nthat even this \"exact fundamental science\" is only accessible to pure\nmonism and excludes all dualism. The great regard which mathematics\nenjoys as an exact science in all branches of knowledge is chiefly\ndue to its _formal accuracy_, and to the possibility of expressing\ninfallibly spatial and time quantities in number and mass.\n\nAstronomy is one of the older sciences that took definite shape\nthousands of years ago, and received a solid mathematical foundation.\nObservations of the movements of the planets and eclipses of the\nsun were conducted by the Chinese, Chaldeans, and Egyptians several\nthousand years before Christ. Christ himself had no more suspicion of\nthese great cosmological discoveries than of the systems which the\nGreek natural philosophers had built up three hundred to six hundred\nyears before his birth. After Copernicus had destroyed the geocentric\nsystem in 1543, and Newton had provided a mathematical basis for\nthe new heliocentric system by his theory of gravitation in 1686,\ncosmogony was firmly established in a monistic sense by the _General\nNatural History of the Heavens_ of Kant, and the _M\u00e9canique C\u00e9leste_ of\nLaplace. Since that time there has been no question of the conscious\naction of a Creator in any part of astronomy. Astrophysics has enlarged\nour knowledge of the physical features, and astrochemistry (by means\nof spectrum analysis) of the chemical nature of the other heavenly\nbodies. The monism of the physical universe has now been established.\n\nGeology was not developed into an independent science until towards\nthe end of the eighteenth century, and did not extinguish the earlier\nnotion of the creation of the earth until after 1830, when the\nprinciple of continuity and evolution was established. The oldest\npart of the science is mineralogy; the great practical value of the\nrocks, and especially the metals obtained from them, having appealed to\nman's interest thousands of years ago. In the Stone Age, Bronze Age,\nIron Age, etc., the material for weapons and tools was provided by\nstone and metal. Afterwards the development of mining led to a closer\nacquaintance with these metals. But no notice was taken of the fossil\nremains of animals and plants until the close of the Middle Ages. It\nwas not until the eighteenth century that students began to perceive\nthe great significance of these \"creation-medals,\" and at the beginning\nof the nineteenth paleontology arose as an independent science, and\nproved equally important to geology and biology. Other branches of\ngeology, such as crystallography, have also made considerable progress\nduring the last half-century, with the aid of physics and chemistry.\nAll these sections of geology, especially geogeny, or the science of\nthe natural development of the earth, are now recognized to be purely\nmonistic sciences.\n\nIn the five branches of science I have enumerated, pure monism has\nbeen universally and exclusively admitted (as far as they relate to\ninorganic nature) in the second half of the nineteenth century. There\nis no question in them to-day of the wisdom and power of the Creator.\nThis is equally true of geology, astronomy, mathematics, chemistry,\nand physics. It is otherwise with the remaining sciences which deal\nwith organic nature; in these we have not yet succeeded in giving a\nphysical explanation and mathematical formulation of all phenomena.\nHence vitalism enters with its dualistic notions, and splits the\nscience into two different branches--natural science (physics in the\nwider sense) and mental science (metaphysics); fixed natural laws are\nsupposed to rule only in the former, while in the latter we still have\nthe \"freedom\" of the spirit and the supernatural. This applies, first\nof all, to biology in the broadest sense (including anthropology and\nall the sciences that relate to man). In the preceding chapters of\nbiological philosophy we have sought to refute vitalism in every form,\nand to secure the exclusive acceptance of monism and mechanicism in\nevery branch of the science of life.\n\nAnthropology is still, as it has been for centuries, taken in many\ndifferent senses. In the widest sense, it embraces the whole vast\nscience of man, just as zoology (in my opinion) deals with all\nparts of the animal world. Since I regard anthropology as a part\nof zoology, I naturally extend the principles of monism to both.\nHowever, this general monistic conception of the science of man has\nmet with only a restricted acceptance up to the present. As a rule,\nthe term \"anthropology\" is restricted to the natural history of man,\nwhich includes the anatomy and physiology of the human organism,\nembryology, prehistoric research, and a small part of psychology. But\nthis \"official anthropology,\" as most of our anthropological societies\n(especially in Germany) conceive it, generally excludes phylogeny, the\ngreater part of psychology, and all the mental sciences, which are\nregarded as metaphysical in the narrower sense. I endeavored to show in\nmy _Anthropogeny_ thirty years ago that man (as a placental mammal of\nthe order of primates) is no less unified an organism (with body and\nsoul) than any other vertebrate, and that, therefore, every aspect of\nhis being should be dealt with monistically.\n\nAs is well known, the views of experts and laymen alike are very much\ndivided as to the place of psychology in the scheme of the sciences.\nThe great majority of the professional psychologists, and of educated\npeople generally, adhere still to the antiquated dogma, with its\nreligious foundation, that man's soul is immortal and an independent\nimmaterial entity. This dualistic view has been supported in the\nschools especially by the authority of Plato, Descartes, and Kant; in\nreligion by the authority of Christ, Paul, and Mohammed; in education\nand the state by the authority of most governments; and in physiology\nby most of the older, and even some recent, physiologists. On this\nview, psychology is a special mental science, having only an external\nand limited connection with natural science. But modern comparative\nand genetic psychology, the anatomy and physiology of the brain,\nhave, in the course of the last forty years, established the monistic\nview that psychology is a special branch of cerebral physiology, and\nthat therefore all its parts and their application belong to this\nsection of biology. The soul of man is a physiological function of\nthe phronema. As I have fully explained the monistic conception of\npsychology in chapters vi.-xi. of the _Riddle_, and supported it with\nall the arguments of anatomy, physiology, ontogeny, and phylogeny in my\n_Anthropogeny_, I need not go further into the subject.\n\nThe science of language shares the fate of its sister, psychology;\nby one section of its representatives it is taken monistically as a\nnatural science, and by another section it is dualistically conceived\nas a branch of mental science. On the old metaphysical view, speech was\nregarded as an exclusive property of man, either a gift of the gods or\nan invention of social man. But in the course of the nineteenth century\nthe monistic and physiological position that speech is a function\nof the organism, and has been gradually developed like all other\nfunctions, has been established. The comparative psychology of the\nhigher animals showed that in various classes the thoughts, feelings,\nand desires of the gregarious animals are communicated partly by signs\nor touch, partly by sounds (the chirrup of the cricket, the cry of the\nfrog, the whistle of many reptiles, song of birds and singing-apes,\nroaring of carnivora and ungulates, etc.). The ontogeny of speech\nshowed that its gradual development in the child is (in accordance\nwith the biogenetic law) a recapitulation of its phylogenetic process.\nComparative philology taught that the languages of the different races\nhave been formed polyphyletically, or independently of each other.\nThe experimental physiology and pathology of the brain showed that a\ndefinite small region of the cortex (the Broca fissure) is the centre\nof speech, and that this central organ, in conjunction with other\nparts of the phronema and the larynx (the peripheral organ), produces\narticulate speech.\n\nHistorical science is, like philology or psychology, still conceived\nin different senses by experts. Very often history is wrongly taken\nto mean the record of events that have occurred in the course of the\ndevelopment of civilized life--the history of peoples and states\n(humorously described as \"the history of the world\"), of civilization,\nof morals, etc. This is merely an anthropocentric feeling that in\nthe strictly scientific sense \"history\" can only be used for the\nrecord of man's doings. In this sense history is opposed to nature,\nthe one dealing with the province of morally free phenomena (with\npreconceived aim), and the other comprising the province of natural\nlaw (without preconceived aim). As if there were no \"natural history,\"\nor as if cosmogony, geology, ontogeny, and phytogeny were not\nhistorical sciences! Although this dualistic and anthropistic view\nstill prevails in our universities, and state and Church protect the\nvenerable tradition, there can be no doubt that sooner or later it\nwill be replaced by a purely monistic philosophy of history. Modern\nanthropogeny shows us the intimate connection between the evolution of\nthe human individual and that of the race; and by means of prehistoric\nand phylogenetic research it joins what is called the history of the\nworld to the stem-history of the vertebrates.\n\nMedicine belongs to the front rank of practical or applied sciences. In\nits long and interesting history it teaches how it is only a monistic\nknowledge of nature, not a dualistic notion of revelation, that affords\nthe foundations of true science and the profitable application of\nthis to the most important aspects of practical life. Medicine was\noriginally the business of the priests, and for thousands of years\nit was under the influence of mystic and superstitious ideas which\nwere connected with religious dogmas. However, two thousand years ago\nthe great physicians of classic antiquity made a serious effort to\nprovide a solid base for medical practice by a thorough anatomic and\nphysiological study of the human frame. But in the general reaction\nof the Middle Ages superstitious and miraculous ideas once more\ndefeated independent scientific investigation. Disease was supposed\nto be the work of evil spirits (as Christ thought) which had to be\nexorcised. Miracles are still thought to take place, even in cultured\ncircles. I need only mention the wonders of patent medicines, magnetic\ncures, Christian Science, and other charlatanry. However, the great\ndevelopment of science in the nineteenth century, especially the\nastonishing advance of biology about the middle of the century,\ngradually shaped medicine into the monistic science which assuages so\nmuch pain and suffering in humanity to-day. Pathology, the science\nof disease, and therapeutics, the rational science of healing, are\ngrounded now on the safe methods of physics and chemistry and a\nthorough knowledge of the human organism. Disease is no longer regarded\nas a special entity that comes on the body like an evil spirit or\nmysterious organism, but is conceived as a baneful disturbance of its\nnormal activity. Pathology is only a branch of physiology; it studies\nthe changes that take place in the tissues and cells under abnormal and\ndangerous conditions. When the causes of these changes are poisons or\nforeign organisms (such as bacteria or am\u0153b\u00e6), the art of healing\nhas to remove them and restore the normal equilibrium of the functions.\n\nThe science of mental disease is a special branch of medicine; it has\nthe same relation to it as psychology has to physiology. However, as\npathological psychology it deserves special consideration, not only\non account of its extreme practical importance, but also because of\nits theoretical interest. The misleading dualist idea of body and soul\nthat has perverted our notions of mental life from the oldest times\nhas led people to regard mental disorders as special phenomena, at one\ntime directly as evil spirits that enter from without into the human\nbody, at another time as mysterious dynamic occurrences affecting the\nmystic being of the soul (independently of the body). These dualistic\nand still wide-spread and mischievous errors have caused the most\nfatal mistakes in the treatment of mental disease; they have had the\nmost unfortunate effect on juristic and social and other aspects of\npractical life. But the ground has been cut from under these irrational\nand superstitious ideas by modern psychiatry, which regards all mental\ndisease as a disorder of the brain, and traces it to changes in the\ncortex that lie at the root of all psychoses (delusions, lunacy,\netc.). As we call this central organ of mind the phronema, we may say:\nPsychiatry is the pathology and therapeutics of the phronema. In many\ndisorders we have already succeeded in anatomically and chemically\ntracing the changes in the psychic or phronetal cells (the neurona\nin the phronema). These acquisitions of the pathological anatomy and\nphysiology of the phronema have a great philosophic interest, because\nthey throw a good deal of light on the monistic conception of psychic\nlife. As the greater part (sixty to ninety per cent.) of these diseases\nare hereditary, and they have mostly been acquired gradually by the\nancestors of the patient, they also afford clear proof of progressive\nheredity, or the inheritance of acquired characters.\n\nThousands of years ago, when barbaric races began to adapt themselves\nto civilized life, they had a concern for their bodily health and\nstrength. In classic antiquity the care of the body by baths, gymnastic\nexercises, etc., was greatly developed, and connected with religious\nceremonies. The splendid aqueducts and baths of Greece and Rome show\nhow much importance they attached to the external and internal use of\nwater. The Middle Ages brought reaction in this province like so many\nothers. As Christianity depreciated this life and said it was merely a\npreparation for the life to come, it led to a disdain of culture and\nof nature; and as it regarded man's body only as the temporary prison\nof his immortal soul, it attached no importance to the care of it. The\nfrightful plagues that swept away millions of men in the Middle Ages\nwere only fought with prayer, processions, and other superstitious\ndevices, instead of with rational hygienic and sanitary measures. We\nhave only gradually learned to discard this superstition. It was not\nuntil the second half of the nineteenth century that a sound knowledge\nof the physiological functions and environment of the organism induced\npeople once more to have a concern for bodily culture. All that modern\nhygiene now does for the public health, especially the improvement of\nthe dwellings and food of the poorer classes, the prevention of disease\nby healthier habits, baths, athletics, etc., can be traced to the\nmonistic teaching or reason, and is altogether opposed to the Christian\nbelief in Providence and the dualism connected therewith. The maxim of\nmodern hygiene is: God helps those who help themselves.\n\nThe remarkable progress of technical science in the nineteenth\ncentury, which has stamped our age as \"an age of machinery,\" is a\ndirect consequence of the immense advance of theoretical science.\nAll the privileges and comforts which modern life gives us are due\nto scientific discoveries, especially in physics and chemistry.\nWe need only recall the enormous importance of steam and electric\nmachinery, modern mining, agriculture, and so on. If by these means\nmodern industry and international commerce have prospered beyond all\nexpectations, we owe this to the practical application of empirical\ntruths. \"Mental science\" and metaphysical speculation have had nothing\nto do with it. There is no need of further proof that all the technical\nsciences have a purely monistic character, like their exact sources,\nphysics and chemistry.\n\nThe scientific development of education is one of the greatest tasks\nof modern civilization. The ideas that are impressed on the mind in\nearly youth are most persistent, and generally determine the direction\nof thought and conduct for the whole of life. Hence we find the\nstruggle between the two philosophic tendencies assuming the greatest\npractical importance in this department. As the priests were, thousands\nof years ago, in the first stages of civilization, the sole trainers\nof the growing mind, they had charge of the school as well as of\nmedicine. Religion was made the chief foundation of instruction, and\nits doctrines were the moral guide for the whole of life. The isolated\nattempts that were made by monistic philosophy in ancient times to\ndestroy this theistic superstition had no effect on the education of\nthe young. In this the dualistic principles of Plato and Aristotle\nprevailed, their metaphysical theories being blended with the teaching\nof the Church. In the Middle Ages the power of the Roman priesthood\nenforced them everywhere. And, although a good deal of this teaching\nlost its prestige at the Reformation, the influence of the Church on\nthe school was maintained down to our own time. The spiritual power of\nthe Church finds a useful ally in this in the conservative attitude\nof most governments. Throne and altar support each other; both dread\nthe advance of scientific inquiry. In face of this powerful dualistic\nalliance, supported by the mental apathy of the masses and a convenient\nblind submission to authority, the monistic system has a difficult\nposition to maintain. It will only gain solid ground in education when\nthe school is divorced from the Church and scientific knowledge is made\nthe foundation of the curriculum. I have pointed out in the nineteenth\nchapter of the _Riddle_ the guiding principles to be followed in this\nreform of education in opposition to the influence of Church and state.\n\nAs we have dealt in the eighteenth chapter with morals and their\ndevelopment from habit and adaptation, we need only mention here the\ncontradiction that we still find between the monistic claims of pure\nreason and the dualistic claims of practical reason. This has been\nlargely sustained by Kant's teaching, but his categorical imperative\nhas been completely refuted by modern science. The metaphysical\ngrounding of morality on free will and ethical intuitions (_a\npriori_) must be replaced by a physiological ethic, based on monistic\npsychology. As this can no more recognize a moral order of the world\nin history than a loving Providence in the life of the individual,\nthe monistic morality of the future must be reducible to the laws of\nbiology, and especially of evolution.\n\nThe great importance that attaches to the new science of sociology is\ndue to its close relations to theoretical anthropology and psychology\non the one hand, and to practical politics and law on the other. When\nwe take it in the wider sense, human sociology joins on to that of\nthe nearest mammals. The family life, marriage, and care of the young\nin the mammals, the formation of herds in the carnivora and ungulates\nand of troops in the social apes, lead on to the looser associations\nof savages and barbarians, and from these to the beginnings of\ncivilization. The history of these associations is connected with\nthe social rules that govern the intercourse of smaller and larger\ncommunities. In the biological reduction of social rules to the natural\nlaws of heredity and adaptation, dynamic sociology (as Lester Ward\nhas called it) proceeds on purely monistic lines, while in social\nintercourse itself we still find a good deal of dualism. How little\ntruth and nature count for in our cultured society, how much hypocrisy\nand insincerity have to do with social rules, has been well shown by\nMax Nordau in his _Conventional Lies of Civilization_.\n\nPolitics is closely connected with sociology on the one hand and\nlaw on the other. As internal politics it controls the organization\nof the state by a constitution; as external or foreign politics it\ndirects the relations of states to each other. In my opinion, pure\nreason should prevail in both departments; the relations of the\ncitizens to each other and to the whole should be regulated by the\nsame ethical principles that we recognize in personal intercourse. We\nare, unfortunately, very far from this ideal in the life of a modern\nstate. Brutal egoism rules in foreign politics; every nation thinks\nonly of its own advantage, and furthers it with all its military and\nother resources. Domestic politics is still largely directed by the\nbarbaric prejudices of the Middle Ages. Great struggles are in progress\nbetween the central government and the mass of the people. Both parties\nspend themselves in fruitless conflicts; yet reason in the life of the\nstate suffers more than its special political complexion. \"Whether the\nstate shall be a monarchy or a republic, aristocratic or democratic,\nare subordinate questions. The great question is: Shall the modern\nstate be spiritual or secular? Shall it be governed _theocratically_ by\nirrational beliefs and clerical arbitrariness, or _nomocratically_ by\nrational laws and civic right?\" (_Riddle_, chapter i.).\n\nIn the science of law, too, we find the prevalence of the dualistic\nprinciples that have come down from the Middle Ages and antiquity, and\nhave acquired a certain sacredness by blending with the teaching of\nthe Church. Kant's dualism is again found to be at work, influencing\nthe ideas of jurists and statesmen. With it we find in our codes many\ncarefully preserved relics of medi\u00e6val superstition. A great deal of\nharm is done by this religious influence. Every day we read in the\npapers of curious deliverances in the lower and higher courts at which\nevery thoughtful man can only shake his head. Here also there will be\nno solid improvement until the education of jurists includes a thorough\ntraining in anthropology and psychology as well as in the code.\n\nTheology has stood at the head of the four venerable \"faculties\" at\nour universities for centuries. It still holds this place of honor,\nas the Church, the organ of practical theology, continues to exercise\na profound influence on life. In fact, most of the other branches\nof applied science--especially jurisprudence, politics, ethics, and\npedagogics--are still more or less affected by religious prejudices.\nThe chief of these is the idea of God conceived in some form or other\nas the Supreme Being; as Goethe says, \"Every one calls the best he\nknows his God.\" However, the idea of God is not the chief feature\nof all religions. The three greatest Asiatic religions--Buddhism,\nBrahmanism, and Confucianism--were at first purely atheistic; Buddhism\nwas at once idealistic and pessimistic, whence Schopenhauer regarded\nit as the highest of all religions. On the other hand, belief in a\npersonal God is the central feature of the three great Mediterranean\nreligions. This anthropomorphic God is conceived in a hundred forms in\nthe various sects of the Mosaic, Christian, and Mohammedan religions,\nbut his existence remains one of the chief articles of faith. No\nevidence of his existence is to be found; this was very ably shown by\nKant, although he thought that practical reason postulated it. All that\nrevelation is supposed to teach us on the matter belongs to the region\nof fiction. The whole field of theology, especially dogmatic theology,\nand the whole of the Church teaching based on it, are based on\ndualistic metaphysics and superstitious traditions. It is no longer a\nserious subject of scientific treatment. On the other hand, comparative\nreligion is a very important branch of theoretical theology. It deals\nwith the origin, development, and significance of religion on the\nbasis of modern anthropology, ethnology, psychology, and history. When\nwe study without prejudice the results of these sciences bearing on\nreligion, theology turns out to be pantheism, in the sense of Spinoza\nand Goethe, and thus monism becomes a connecting link between religion\nand science.\n\nThis brief survey of the twenty chief branches of modern science\nand their relation to monism and dualism shows that we are face to\nface with great contradictions, and that we are still far from the\nharmonious and successful adjustment of these differences. They are\npartly due to a real antinomy of reason in the Kantist sense--an\nantithesis in ideas, in which the positive seems to be just as\ncapable of proof as its contradictory. But, for the most part, this\nunfortunate antinomy in the sciences is connected with their historical\ndevelopment. Pure reason, the highest quality of civilized man, was\ngradually evolved from the intelligence of the savage, and this in turn\nfrom the instincts of the apes and lower mammals; and many relics of\nits former lower condition remain to-day, and have, through practical\nreason, a most prejudicial influence on science. These dualistic\nprejudices and irrational dogmas--intellectual residua of the primitive\ncondition of the race, fossil ideas and rudimentary instincts--still\npervade the whole of modern theology, jurisprudence, politics, ethics,\npsychology, and anthropology. If we glance at the whole field of modern\nscience at the beginning of the twentieth century in this connection,\nwe can distribute its twenty sections into three groups--rational\n(purely monistic), semi-dogmatic (half-monistic), and dogmatic\n(predominantly dualistic) disciplines.\n\nThe following may be classed as rational or purely monistic sciences,\nin which no competent and thoroughly expert representative now admits\ndualistic considerations: of the pure or theoretical sciences, physics,\nchemistry, mathematics, astronomy, and geology; of the applied or\npractical sciences, medicine, hygiene, and technology. On the other\nhand, in the semi-dogmatic sciences we still find a mixture of\nmonistic and dualistic ideas in the appreciation of their aims and\nobjects, one or the other prevailing according to the party position\nor personal training of the individual representative. This is the\ncase with most of the biological sciences, biology (in the broadest\nsense), anthropology, psychology, philology, history, psychiatry;\nand of the applied sciences, pedagogics and ethics. The two latter\nsciences form a transition to the four purely dogmatic sciences in\nwhich the traditional dualism is still paramount: sociology, politics,\njurisprudence, and theology. In these branches of science medi\u00e6val\ntraditions retain a good deal of their power. Most of their official\nrepresentatives cling to prejudices and superstitions of all sorts,\nand very slowly and gradually admit the acquisitions of pure reason as\nembodied in monistic anthropology and psychology. The intellectual life\nwas in many respects more advanced at the beginning of the nineteenth\nthan of the twentieth century.\n\nThis classification of the chief branches of knowledge in their\nrelation to philosophy, the comprehensive science of general truths,\nis naturally only a provisional and personal sketch. It is especially\ndifficult from the circumstance that all the sciences have very complex\nrelations to each other, and have undergone many changes as to their\naims and subjects in the course of their historical development. I\nwill only point out that a good deal of science--in fact, the rational\nsciences with exact mathematical basis--have now been completely won\nover to monism; and in the semi-dogmatic sciences it is gaining ground\nfrom day to day, so that we may hope sooner or later to see the four\ndogmatic sciences also, the strong bulwarks of dualism--sociology,\npolitics, jurisprudence, and theology--succumb to monism. For the\nultimate aim of all the sciences can only be the unity of their\nunderlying principles, or their harmonious unification by pure reason.\n\nIt is now more and more generally acknowledged in educated countries\nthat a complete reform of our educational curriculum is needed,\nboth in elementary and secondary schools and at the universities.\nThe great struggle between two different tendencies assumes larger\nproportions every day. On the one hand, most governments, following\ntheir conservative instinct, cling as far as possible to medi\u00e6val\ntraditions, and find support in the dogmatic teaching of theology\nand jurisprudence. On the other hand, the representatives of pure\nreason seek to get rid of these fetters, and to introduce the\nempirical and critical methods of modern science and medicine into\nwhat are called the mental sciences. The opposition between the two\nparties is accentuated by their different sociological tendencies.\nLiberal humanists claim that the freedom and education of all men is\nthe aim of progressive evolution, in the conviction that the free\ndevelopment of the personality of each individual is the surest\nguarantee of happiness. To conservative governments this is a matter of\nindifference; they look on the individual citizens, in accordance with\nthe manifold division of labor, merely as so many screws and wheels in\nthe great organism of the state. The \"upper ten thousand\" naturally\nthink of their own welfare first, and desire to keep all higher\neducation to themselves. But in the light of pure reason the state is\nnot an end in itself; it is a means to insure the prosperity of the\ncitizens. To each of these, whatever their condition, the opportunity\nshould be afforded of acquiring the higher education and developing\ntheir talents. Hence in education we should impart a general outlook\non all the sides of human life. Each should acquire the elements of\nscience, not only of physics and chemistry, but also of biology and\nanthropology. On the other hand, the predominance of the classical\ntraining over modern ought to be restricted. Every student and every\nfaculty should be occupied with only philosophy and science in the\nfirst sessions, and not take up special studies until afterwards.\n\nAt the close of the _Riddle_ I brought out in clear relief the\nantagonism between modern monism and traditional dualism, but also\npointed out that\n\n this strenuous opposition may be toned down to a certain degree\n on clear and logical reflection--may, indeed, be converted into a\n friendly harmony. In a thoroughly logical mind, applying the highest\n principles with equal force in the entire field of the cosmos--in\n both organic and inorganic nature--the antithetical positions of\n theism and pantheism, vitalism and mechanism, approach until they\n touch each other. Unfortunately, consecutive thought is a rare\n phenomenon in nature.\n\nThis conciliatory disposition has grown stronger and stronger in\nme. Every year increases my belief that the dualism of Kant and the\nprevalent metaphysical school must give way to the monism of Goethe and\nthe rising pantheistic tendency. In this we do not lose sight of our\nideals. On the contrary, our \"realist philosophy of life\" teaches us\nthat they are rooted deep in human nature. While occupying ourselves\nwith the ideal world in art and poetry, and cultivating the play of\nemotion, we persist, nevertheless, in thinking that the real world,\nthe object of science, can be truly known only by experience and pure\nreason. Truth and poetry are then united in the perfect harmony of\nmonism.\n\n\n\n\nINDEX\n\n\n Abiogenesis, 339-358;\n may still occur, 357.\n\n Abiology, 27, 78.\n\n Abortion, 325.\n\n Abstraction, power of, 316.\n\n Achromin, 140, 142.\n\n Acquired characters, inheritance of, 367-369, 376.\n\n Actinal beauty, 185.\n\n Active movements in organisms, 262.\n\n Adaptation, 415.\n\n \u00c6sthesis, 296, 308.\n\n \u00c6sthetal cells, 14.\n\n \u00c6sthetic selection, 422.\n\n Agassiz on the creation of species, 30.\n\n Agnostic position on the origin of life, 338.\n\n Albumin, 39, 126, 128.\n\n Albuminoids, the, 39, 125, 126.\n\n Alg\u00e6, 161, 195, 220.\n\n Alimentary system, the, 227.\n\n Allopola, 174.\n\n Alternation of generations, 253.\n\n Altmann on the structure of plasm, 134.\n\n Altruism, sources of, 115.\n\n Ambulacral system, 280.\n\n Am\u0153boid movements, 268.\n\n Amphigony, 240.\n\n Amphimixis, 244.\n\n Amphithecta, 176.\n\n Angiophyta, 220.\n\n Animal states, 36, 148, 150, 168.\n\n Animals, kindness to, 115;\n younger than plants, 216.\n\n Animism, 58.\n\n Annelids, motor apparatus of the, 281.\n\n Antheridia, 249.\n\n Anthophyta, 162, 220.\n\n _Anthropogeny, The_, 283, 320.\n\n Anthropogeny, the science of, 321, 332.\n\n Anthropologists and evolution, 321.\n\n Anthropology, 86, 478.\n\n Antivitalism, 50.\n\n Ape, mind in the, 332, 333.\n\n Apes and men, common structure of, 285.\n\n Aphanocapsa, 32, 130, 182, 196, 205.\n\n Apostles' Creed, the, 60-65.\n\n Apotelia, 163.\n\n Apposition, 42.\n\n Archegonia, 249.\n\n Archigony, 341-358;\n formulation of, 355, 356;\n repetition of, 356;\n statement of grounds, 341;\n theories of, 343-348.\n\n Archiplasm, 129, 142, 158.\n\n Aristotle, 66.\n\n Art, modern development of, 407.\n\n Articulates, motor apparatus of the, 282.\n\n Articulation, 281.\n\n Asexual generation, 241-244.\n\n Assimilation, 42, 211.\n\n Association-centres, 12, 13.\n\n Associational beauty, 185.\n\n Astrolarva, 279.\n\n Astronomy, monism of, 457.\n\n Astrozoon, 280.\n\n Asymmetrical types, 179.\n\n Auditory vesicles, 311.\n\n Autogony, 341.\n\n Autonomous movement, 262.\n\n\n Bacilli, 200, 201, 202.\n\n Bacon, the founder of empiricism, 7.\n\n Bacteria, the, 157, 198-206, 218, 234, 235;\n absence of nucleus in the, 200, 201.\n\n Bacteriology, 198.\n\n Baptism, 425, 426.\n\n Barbarians, higher, 395;\n life of, 394;\n lower, 394;\n mental life of, 58;\n middle, 395;\n religion of, 58.\n\n Bar\u00e6sthesis, 309.\n\n Barotaxis, 309.\n\n Bathybius Haeckelii, 207.\n\n Beauty, evolution of the sense of, 188;\n sources of, 184;\n stages of, 184-187.\n\n Beggiatoa, 199, 205, 218.\n\n Berzelius on catalysis, 44.\n\n Bilateral-radial types, 177.\n\n Bilateral symmetry, 177.\n\n Bioblasts, 134.\n\n Bio-crystals, 41.\n\n Biogen-hypothesis of Verworn, 46, 137, 138.\n\n Biogens, 102, 128, 137, 192.\n\n Biogenetic law, the, 380-382, 384.\n\n Biogeny, 94, 360.\n\n Biology, division of, 94;\n sphere of, 27, 78.\n\n Bionomy, 78, 95.\n\n Bionta, 149, 151;\n virtual, 151;\n partial, 151.\n\n Biophora, 137.\n\n Biotonus, 103.\n\n Blastoderm, the, 161.\n\n Botanists and zoologists, divergence of, 374.\n\n Brain, as an organ of mind, 25;\n evolution of the, 22, 327, 328.\n\n Brownian movement, 260.\n\n Bryophyta, 162.\n\n Budding, 242, 243.\n\n Bunge, as vitalist, 50.\n\n B\u00fctschli on the monera, 31;\n on the structure of plasm, 132.\n\n\n Calymma, the, 270.\n\n Canon law, the, 324, 325.\n\n Carbon assimilation, 34, 130, 212, 213, 342.\n\n Carbon, importance of, 37, 38.\n\n Caryokinesis, 139, 267.\n\n Caryolymph, 141, 142.\n\n Caryolysis, 268.\n\n Child, mind of the, 90, 323.\n\n Child-soul, study of the, 20.\n\n Children, destruction of incurable, 21, 120.\n\n Chitine, 282.\n\n Chlorophyll, 33, 141, 195, 214.\n\n Chorology, 95.\n\n Chromacea, 32, 130, 137, 157, 182, 194-197;\n description of the, 194;\n structure of the, 197.\n\n Chromatella, 33, 343.\n\n Chromatin, 140, 142.\n\n Chromatophora, 33, 343.\n\n Chromoplasts, 141, 196.\n\n Chroococcacea, the, 32, 182.\n\n Chroococcus, 32, 130, 182, 196, 197, 208.\n\n Ciliary movement, 272, 276.\n\n Circulation of the blood, 228.\n\n Civilization, characteristics of, 58-59;\n evils of, 114;\n growth of, 334;\n modern, 335, 402;\n shades of, 401, 408;\n stages of, 398;\n progress of, 469;\n value of, 309.\n\n Civilized races, higher, 397;\n life of, 396;\n lower, 396;\n middle, 396;\n mind in, 334.\n\n Cleanliness in antiquity, 464.\n\n Clothing, beginning of, 423;\n fashions in, 430.\n\n Cnidaria, 224;\n generation of the, 250, 253.\n\n C\u0153lenteria, 166, 221, 223, 225.\n\n C\u0153loma, the, 223, 225.\n\n C\u0153lomaria, 166, 221, 225.\n\n C\u0153nobia, 160, 161.\n\n Colloids, nature of, 39.\n\n Colon, the, 226.\n\n Coloring methods, 208.\n\n Conjugation, 246.\n\n Consciousness a function of the brain, 331;\n development of, 331;\n nature of, 19, 23, 290, 291.\n\n Conservatism of governments, 73.\n\n Contact-action, 45.\n\n Copulation, 251.\n\n Cormophyta, 165, 167.\n\n Cormus, 36, 148, 150, 154, 168, 184.\n\n Corset, the, 430.\n\n Cortex of the brain, 12, 323, 327, 329.\n\n Cosmic intelligence, 30;\n monism, 37.\n\n Cosmogony, 360.\n\n Cosmokinesis, 266.\n\n Craniota, mind in the, 326.\n\n Creationism, 337.\n\n Crustacea, parasitic, 237.\n\n Crystals, 41;\n forms of, 172;\n growth of, 42, 43;\n life of, 41;\n and organisms compared, 35, 40, 41, 43, 44;\n reproduction of, 44.\n\n Crystallization, 265, 266.\n\n Crystalloids, nature of, 39.\n\n Culmus, the, 165, 183.\n\n Cultivated races, definition of, 397;\n higher, 400;\n lower, 398;\n middle, 399.\n\n Custom, tyranny of, 421.\n\n Cuticle, 146.\n\n Cyanogen, 346.\n\n ---- theory, 347.\n\n Cytodes, 33, 157, 192, 194.\n\n Cytology, 128, 190.\n\n Cytophyta, 220.\n\n Cytoplasm, 35, 122, 138, 139, 142, 158, 191.\n\n Cytosoma, 122, 138.\n\n Cytotheca, 145.\n\n Cytula, 244.\n\n\n Darwin on the origin of life, 338.\n\n Darwinism, 50, 80, 361, 363, 364, 373.\n\n De Bries on heredity, 373.\n\n Death, nature of, 98;\n of the unicellulars, 99;\n of the histona, 100;\n real cause of, 101;\n total and partial, 105.\n\n Decomposability of plasm, 345.\n\n Descartes' idea of the soul, 16, 18.\n\n Descriptive science, 4, 5, 6.\n\n Design, argument for, 388.\n\n Dialysis, 39.\n\n Diatomes, 41, 182.\n\n Diclinism, 247.\n\n Di\u0153cia, 248.\n\n Disassimilation, 212.\n\n Disease, nature of, 106.\n\n Dissogony, 252.\n\n Division of labor, 35;\n in the cell, 143, 158;\n in the organism, 149, 167;\n in the state, 150, 169.\n\n Divorce, 428, 429.\n\n Dogmatic sciences, 470.\n\n Dominants, the, of Reinke, 264.\n\n Driesch, as vitalist, 51.\n\n Dualism, 81, 91, 433.\n\n Dualistic view of life, 337, 348, 366;\n of the mind, 332;\n of morality, 411;\n of sensation, 446, 447.\n\n Dumas, Louis, as vitalist, 47.\n\n Duty an evolved sense, 413.\n\n Dwarf races, 422.\n\n Dynamism, 85, 110.\n\n\n Ear, canals in the, 311;\n the, 312.\n\n Echinoderms, motor organs of the, 279-281.\n\n Ectogenesis, 369.\n\n Education, reform of, 471;\n struggle over, 465.\n\n Egoism, 115, 403;\n and altruism, 419.\n\n Elasticity, 310.\n\n Eleatic philosophers, the, 66.\n\n Electric organs, 313.\n\n Electricity, sensation of, 312, 313.\n\n Elements, chemical, 37, 38.\n\n Embryo, legal view of the, 325, 326;\n mind in the, 325.\n\n Embryology, 20, 21;\n mechanical, 383.\n\n End of life, 387.\n\n Energism, 85.\n\n Energy as attribute of substance, 446, 449;\n definition of, 449.\n\n Enzyma, 46, 128.\n\n Epicureanism, 83.\n\n Epitelia, 163.\n\n Epithelium, ciliated and flagellated, 276.\n\n Erect posture, the, 285.\n\n Ergology, 95.\n\n Ergonomy, 35, 150.\n\n Erotic chemotropism, 306.\n\n Eternity hypothesis of life, 338.\n\n Ethic, the perfect, 400.\n\n Ethics, 411.\n\n Eucharist, the, 426.\n\n Excretion, 232, 233.\n\n Experience, importance of, 3, 4.\n\n Experiment, limited use of, 352, 353, 383;\n nature of, 7, 8.\n\n Experimental science, 4, 8.\n\n Extension, 446, 448.\n\n Eye, the, 298;\n evolution of, 298, 299.\n\n\n Faith, 437, 439;\n natural and supernatural, 54.\n\n Family, evolution of the, 402.\n\n Fashion, 422.\n\n Fechner on sensation, 295;\n on the universality of life, 340.\n\n Feeling, 296, 308.\n\n Fetichism, 57, 58.\n\n Filar theory of plasm, 134.\n\n Fistella, 344.\n\n Flagelliform movement, 271, 276.\n\n Flame, analysis of the, 28.\n\n Flat-fishes, metamorphosis of, 178.\n\n Flechsig, discoveries of, 13.\n\n Flemming on the structure of plasm, 113.\n\n Food, artificial production of, 400.\n\n Forms of organic structure, 173-184.\n\n Frommann on plasm, 133.\n\n Frothy theory of plasm, 132, 133.\n\n Fungi, 162, 204, 215, 234, 236.\n\n Fungilli, 204, 235.\n\n\n Gameta, the, 244.\n\n Gastr\u00e6a theory, the, 223.\n\n Gastr\u00e6ads, 223.\n\n Gastric canal, 228.\n\n Gastro-canal system, 222, 223.\n\n Gastrula, the, 166.\n\n Gemmation, 242, 243.\n\n Genealogy of organisms, 304, 305, 376.\n\n Generation, sexual and asexual, 241-251.\n\n Geogeny, 360.\n\n Geology, historical nature of, 378;\n monism of, 458.\n\n Geotropism, 310.\n\n Germ-plasm, 143;\n the theory of, 367, 372.\n\n German mind, Janus character of, 441.\n\n Gills, 229, 230.\n\n Globular shape, origin of, 34.\n\n Gl\u0153ocapsa, 32, 196, 205.\n\n Goethe, monism of, 442;\n realism of, 440;\n scientific studies of, 440, 441.\n\n Gonades, 249.\n\n Gonochorism, 246.\n\n Gonoducts, 250.\n\n Granular theory of plasm, 134.\n\n Gravitation, sensation in, 309.\n\n Growth, 241.\n\n Growth movements, 264.\n\n\n Habit, 415-417;\n in inorganic bodies, 417.\n\n Heart, the, 228;\n work of the, 277.\n\n Heat, sensation of, 300, 301.\n\n Heaven, 109.\n\n Hedonism, 84.\n\n Heliotropism, 298.\n\n Helmholtz on the origin of life, 339.\n\n Heraclitus on life, 28.\n\n Heredity, conservative and progressive, 368;\n cumulative, 369;\n theories of, 135, 136, 366.\n\n Hermaphrodism, 245, 246, 258, 259.\n\n Hermaphroditic glands, 249.\n\n Hertwig, O., on the biogenetic law, 382;\n on the monera, 31.\n\n Heterogenesis, 254.\n\n His, W., theories of, 383.\n\n Histolysis, 106.\n\n Histona, the, 36.\n\n Histonals, 165, 166, 171, 182.\n\n Historical waves, 389.\n\n History, 461;\n nature of, 9;\n sources of, 9.\n\n Hofmeister on organic chemistry, 45.\n\n Holosph\u00e6ra, 173.\n\n Honor, false sense of, 430.\n\n Huxley on organic individuality, 152.\n\n Hyaloplasm, 130, 143.\n\n Hybrids, 255, 256;\n fertility of, 255.\n\n Hydrostatic movements, 270.\n\n Hygiene, 401, 464.\n\n Hylonism, 82.\n\n Hylozoism, 81, 86, 451.\n\n Hypogenesis, 255.\n\n Hypotheses, nature of, 54;\n necessity for, 86, 87, 89, 378, 439.\n\n\n Idealism, theoretical and practical, 84, 92.\n\n Idiocy, 20.\n\n Idioplasm theory, the, 136, 137, 366, 367.\n\n Ileum, the, 226.\n\n Imagination, function of the, 87.\n\n Imbibition energy of plasm, 39.\n\n Imbibition in organisms, 261.\n\n Immaterial world, the, 436, 437.\n\n Immortality, the belief in, 64, 65, 71, 108;\n of the unicellulars, 99-101.\n\n Incurables and suicide, 118, 119.\n\n Individuality, organic, 149, 152.\n\n Infusoria, movement in the, 268, 269, 272.\n\n Inoculation, 204.\n\n Insanity, increase of, 114, 118, 119.\n\n Insectivorous plants, 304, 305.\n\n Instinct, 418.\n\n Intelligence, 316, 317.\n\n Intercellular matter, 145.\n\n Intussusception, 42.\n\n Ionic philosophers, the, 66.\n\n Irritability, 287, 288, 291, 293.\n\n Isopola, 174.\n\n\n Kant as natural historian, 9;\n biological ignorance of, 11, 318, 319;\n critical views of, 438;\n contradictory views of, 68, 434, 444;\n influence of, 25;\n mechanical views of, 435;\n moral philosophy of, 412, 413;\n mystic training of, 443;\n narrow life of, 443;\n philosophy of, 68, 69, 74, 434-440;\n popularity of, 444;\n theory of knowledge of, 9, 10, 69, 317-319, 332.\n\n Kassowitz on archigony, 355.\n\n Kelvin, Lord, on the origin of life, 339.\n\n Kidneys, the, 233.\n\n Kirchhoff on the work of science, 6.\n\n Knowledge, _a priori_ and _a posteriori_, 11, 24, 317;\n and faith compared, 54;\n dualistic\n theory of, 24;\n monistic theory of, 12-14.\n\n Kusamaul on the child-soul, 30.\n\n\n Lamarck, 79.\n\n Lamarck's transformism, 363.\n\n Landscape beauty, 187.\n\n Lange on Kant, 439.\n\n Larv\u00e6, 253.\n\n Law, beginning of idea of, 420;\n reaction in science of, 401.\n\n Leibnitz, philosophy of, 110.\n\n Leucocytes, 228;\n and bacteria, 305.\n\n Lichens, 238.\n\n Life, artificial production of, 352, 358;\n as a flame, 28, 29;\n constant change of, 386, 387;\n evolution of, 360-365;\n length of, 101;\n nature of, 27, 343;\n origin of, 337-358;\n value of, 386-410.\n\n Light, action of, 297-300.\n\n Living substance, 36, 123.\n\n Lobmonera, 206.\n\n Localization of functions, 17, 19, 20;\n of mental functions, 328, 329.\n\n Locomotion, 275-285;\n modern progress in, 404.\n\n Lord's Supper, the, 426.\n\n Love, progressive refinement of, 402.\n\n Luminous animals, 312.\n\n Lungs, 230, 231.\n\n\n Machine-theory of life, the, 29, 30, 102.\n\n Macrogameton, 244.\n\n Mammals, common descent of the, 284;\n motor apparatus of the, 283.\n\n Manners and morals, 421.\n\n Marriage, development of, 402, 403;\n evolution of, 427;\n priestly control of, 428.\n\n Materialism, 82, 451.\n\n Mathematics, 456.\n\n Matrimony, 427, 428.\n\n Matter as attribute of substance, 448.\n\n Mechanical embryology, 103.\n\n Mechanics, 259.\n\n Medicine, development of, 462.\n\n Membranes, cellular, 144, 145, 155, 157, 194.\n\n Memory, 416.\n\n Mental disease, evidential value of, 19.\n\n Metabolism, 28,38, 44, 46, 103, 130, 210, 211, 217;\n a mechanical process, 259, 260;\n in the metaphyta, 219-221;\n in the metazoa, 221, 233;\n in the protophyta, 217-219;\n in the protozoa, 219, 220.\n\n Metagenesis, 253.\n\n Metamerism, 167, 168, 281.\n\n Metamorphology, 94.\n\n Metaphysicians disdain physical science, 16.\n\n Metaphysics, nature of, 10, 88, 89.\n\n Metaphyta, 161, 165.\n\n Metaplasm, 106, 129.\n\n Metaplasmosism, 107.\n\n Metasitism 217.\n\n Metazoa, 163.\n\n Micella, 137, 344.\n\n Micrococcus, 201, 202.\n\n Microgameton, 244.\n\n Middle Ages, thought in the, 66, 67.\n\n Mimicry, 421, 422.\n\n Mind, the, 315, 316;\n a function of the brain, 328-330;\n evolution of the, 319, 320, 322, 323, 326.\n\n Miracles, 60;\n in biology, 55;\n nature of, 54.\n\n Mohl, Hugo, 122.\n\n Molecular structure of the monera, 34, 137;\n theories of plasm, 342-346.\n\n Molecules, 126, 127.\n\n Monaxonia, 174.\n\n Monera, the, 31-33, 40, 157, 182, 190-209, 342.\n\n Monism, 81, 433-445.\n\n Monobia, 160, 196.\n\n Monoclinism, 247.\n\n Mon\u0153cia, 248.\n\n Monogamy, 240.\n\n Morality, 411, 412;\n a social instinct, 419, 420;\n conventional, 430;\n evolution of, 413, 414, 430-432;\n a form of adaptation, 414.\n\n Morphology, 94, 171.\n\n Morphonta, 149, 152.\n\n Motion in metabolism, 259.\n\n M\u00fcller, Johannes, on the nature of life, 49;\n on sensation, 288.\n\n Muscles, the, 273, 276-279;\n forms of in lower animals, 278;\n striated and non-striated, 277.\n\n Muscular cells, 277.\n\n Mutation theory, the, 365, 373.\n\n Myoph\u00e6na, 269.\n\n\n N\u00e4geli on evolution, 365;\n on plasm, 137;\n on the origin of life, 343, 344, 354, 356;\n on universality of sensation, 450.\n\n Natural history, 9.\n\n Naturalism, 86, 87.\n\n Necrobiosis, 106, 349.\n\n Neo-Darwinism, 375, 376.\n\n Neo-Lamarckism, 375, 376.\n\n Neovitalism, 48;\n sceptical and dogmatic, 50.\n\n Neurona, 12, 13, 328.\n\n Nitrobacteria, 201, 215, 218.\n\n Nuclein, 156.\n\n Nucleolus, 140.\n\n Nucleus of the cell, 122, 139, 155.\n\n Nutrition, progress in supply of, 401.\n\n\n Observation, subjective and objective, 7.\n\n Occultism, 74, 75.\n\n \u0152cology, 78, 95.\n\n Oken, Lorentz, 79, 80.\n\n Olfactory region, 303.\n\n Ontogeny, 94, 361, 376, 379.\n\n Optimism, 109, 110.\n\n Organella, 35, 130, 159, 163, 191.\n\n Organic chemistry, 37;\n and inorganic, differences between, 27, 28, 40;\n meaning of, 37;\n sensations, 302, 308.\n\n Organism, nature of an, 29, 30, 36.\n\n Organization, nature of, 29;\n progress of, 338;\n stages of, 149, 150, 151.\n\n Organs, 159, 163;\n apparatus of, 164;\n systems of, 164;\n of sense and thought, 12.\n\n Osmosis, 39.\n\n Ostwald, as a monist, 38;\n on enzyma, 46;\n on growth, 44;\n on mental energy, 330;\n system of, 85.\n\n Ovary, 325.\n\n Ovoplasm, 245.\n\n Ovulum, the, 245, 247, 250.\n\n\n P\u00e6dogenesis, 253.\n\n Palavitalism, 48, 49.\n\n Palingenesis, 382.\n\n Pangenesis theory, the, 366.\n\n Panpsychism, 340.\n\n Pantheism, 82.\n\n Paranuclein, 141.\n\n Parasites, 235-238.\n\n Parasitology, 235.\n\n Paratonic movement, 262, 274.\n\n Parthenogenesis, 251, 252.\n\n Passive movements in organisms, 262.\n\n Pasteur disproves spontaneous generation, 350-352.\n\n Paulospores, 244.\n\n Peptones, 45.\n\n Perception of stimuli, 292, 293, 296.\n\n Perigenesis of the plastidules, 136.\n\n Perpetual motion of universe, 258.\n\n Persons, 36, 148, 150, 154, 166, 183.\n\n Pessimism, 109, 110, 111.\n\n Pfl\u00fcger on origin of life, 345, 346, 356.\n\n Philology, 461.\n\n Philosophy, history of, 81;\n modern, defects of, 453;\n nature of, 2, 3, 453, 454.\n\n Phoronomy, 259.\n\n Photo-synthesis, 214, 217.\n\n Phototaxis, 298.\n\n Phronema, the, 14, 15-17;\n structure of the, 329.\n\n Phroneta, the, 13, 329, 331.\n\n Phronetal cells, 14, 17.\n\n Phylogeny, 94, 361, 376, 379;\n sources of, 377.\n\n Physicians, liberal views of, 116-118.\n\n Physics, monism of, 455; nature of, 89, 454.\n\n Physiologists, dualism of, 18.\n\n Physiology, 93.\n\n Phytomonera, 193.\n\n Phytoplasm, 213, 217.\n\n Piano theory of the soul, 16.\n\n Pineal gland, the, 16.\n\n Planospores, 244.\n\n Plants, spontaneous movement in, 274, 275.\n\n Plasm, 121, 123, 128-146;\n chemical constituents of, 125, 126;\n differentiation of the, 138;\n molecules of, 136;\n nature of, 27, 28, 159;\n structure of, 128, 129, 130-138.\n\n Plasma products, 144.\n\n Plasmodomism, 33, 34, 130, 193, 197, 212, 213, 343, 357.\n\n Plasmogony, 354.\n\n Plasmophaga, 193, 196, 200, 212.\n\n Plasson, 158.\n\n Plassonella, 355, 358.\n\n Plastids, 138, 192.\n\n Plastidules, 136.\n\n Plastin, 141.\n\n Plate on Darwinism, 364.\n\n Platnosph\u00e6ra, 174.\n\n Plato, dualism of, 436;\n philosophy of, 66.\n\n Platodes, 225.\n\n Pleuronectides, 178.\n\n Poetry, pedagogical value of, 439.\n\n Poisonous bacteria, 221, 305;\n fungi, 236.\n\n Polioplasm, 130, 143.\n\n Politics, 467.\n\n Polytomy, 243.\n\n Powder, 31.\n\n Pressure, sense of, 310.\n\n Preyer on the child-soul, 20;\n on the earth as an organism, 37;\n on universality of life, 340.\n\n Principle of individuation, 153.\n\n Probionta, 354.\n\n Promorphology, 94, 172.\n\n Protam\u0153ba, 206.\n\n Proteids, 126, 127.\n\n Protestants, liberalism among, 73.\n\n Protists, the, 34, 35, 131, 160, 171, 182, 190-209;\n can endure extreme temperatures, 300;\n movements of the, 267, 271;\n science of the, 92, 93;\n sensitiveness to electricity, 313.\n\n Protoplasm, 32;\n nature of, 121, 122, 125.\n\n Providence, belief in, 107, 108.\n\n Pseudopodia, 268.\n\n Psychiatry, 19, 329, 463.\n\n Psychogenesis, 21.\n\n Psychology, 461;\n comparative, 21, 22;\n modern, errors of, 71;\n monistic, 322;\n nature of, 18.\n\n Psycho-monism, 92.\n\n Psychophysics, 330.\n\n Pteridophyta, 162, 220.\n\n Ptomaines, 203.\n\n Purposive movement, 264, 265.\n\n Pyramidal types, 176.\n\n\n Radiolaria, 41, 156, 172, 181;\n movement in the, 322.\n\n Ranke, J., on evolution, 322.\n\n Rational sciences, 470.\n\n Reaction, 293.\n\n Realism, 90, 91.\n\n Reason, 316, 317;\n pure and practical, 317.\n\n Reason and authority, 423.\n\n Redemption, dogma of, 62.\n\n Reflex movement, 262, 263.\n\n Regeneration, organic, 101-105.\n\n Reinke, as vitalist, 51;\n dualism of, 30;\n on the monera, 31;\n on the origin of life, 337;\n theory of dominants, 264;\n works of, 80, 81.\n\n Release of energy, 294.\n\n Religion, evolution of, 57-65, 420, 421, 424.\n\n Reproduction a monistic process, 257;\n by division, 242;\n nature of, 241.\n\n Respiration, 228-232.\n\n Resurrection, the, 64.\n\n Resurrection plants, 262.\n\n Rhizomonera, 206.\n\n Rhizopods, 129, 192, 193, 219;\n movement in the, 270.\n\n Rhodocytes, 228.\n\n Rhumbler, L., on the cell-life, 132.\n\n Rhythmic beauty, 185.\n\n Richter, H. E., on life, 339.\n\n Rindfleisch, as vitalist, 51.\n\n Romanes, conversion of, 22, 23.\n\n Romanism, 63, 425, 426.\n\n\n Sacraments, 425, 426.\n\n Saposites, 234.\n\n Saprobiosis, 349, 350.\n\n Sarcode, 155.\n\n Savage, mind in the, 56, 57, 90, 333, 391, 405, 406, 424;\n religion of the, 57;\n sense-life in the, 406, 407;\n views of the, 390.\n\n Savages, higher, 394;\n life of the, 392-394;\n lower, 398;\n middle, 393.\n\n Schiller, idealism of, 439, 440-442.\n\n Schizpphyta, 201.\n\n Schleiden, 154.\n\n Schleiermacher, 72.\n\n Schopenhauer, as pessimist, 111, 112;\n on the categorical imperative, 412;\n on suicide, 114.\n\n Schultze, Max, on the cell, 155.\n\n Schwann, 154.\n\n Science, confusion in, 77;\n nature of, 4;\n schools of, 4;\n work of, 5, 6;\n value of, 407, 408.\n\n Science and tradition, conflict of, 70, 71.\n\n Secretory movement, 271.\n\n Selection, theory of, 361, 363.\n\n Self-cleavage, 242.\n\n Self-consciousness, beginning of, 323, 324.\n\n Semi-dogmatic sciences, 470.\n\n Senility, causes of, 106.\n\n Sensation and consciousness, 290, 291, 295.\n\n Sensation as attribute of substance, 447, 448;\n analysis of, 293;\n common to all bodies, 295, 296, 309;\n evolution of, 450;\n in atoms, 83;\n in plants, 292, 304; nature of, 287-293;\n neglected by physiologists, 289, 292;\n of matter, 302;\n universal, 449.\n\n Sensations in savage and civilized man, 405, 406;\n organic, 302, 308.\n\n Sense-centres, 13, 329.\n\n Senses, finer development of the, 406.\n\n Sensibility, 287, 288, 293.\n\n Sensitiveness, 293.\n\n Sensorium, the, 14.\n\n Sensualism, 4, 14, 15.\n\n Sentiment and reason, 120.\n\n Sex sense, the, 245.\n\n Sexual beauty, 186.\n\n ---- characters, secondary, 251.\n\n ---- generation, 244-253.\n\n ---- selection, 251.\n\n ---- sense, the, 306, 307.\n\n Shame, feeling of, 423.\n\n Sight, evolution of, 24.\n\n Silicon, 40.\n\n Skeletal theory of plasm, 113.\n\n Skeleton, common type of the, 371.\n\n ---- the, 278, 279, 283, 284.\n\n Sleep of flowers, 274.\n\n Smell, 303, 304.\n\n Snails, evolution of the, 279;\n muscles of the, 278.\n\n Sociology, 467.\n\n Soul, the, 315, 324;\n dualistic idea of the, 15, 16;\n found in all substance, 397;\n seat of the, 15-18.\n\n Space, nature of, 70;\n sense of, 311.\n\n Spallanzani and spontaneous generation, 350.\n\n Spartan selection, 22, 119.\n\n Specialism, dangers of, 92.\n\n Species, nature of the, 204.\n\n Speech, 461.\n\n Sperm-plasm, 245.\n\n Spermatozoon, the, 245;\n movement of the, 271, 272.\n\n Spinoza, system of, 82;\n monism of, 445.\n\n Spirilla, 202.\n\n Spiritism, 74, 75,\n\n Spiritualism, 451.\n\n Spontaneous generation, 348;\n conflict over, 349, 350;\n older belief in, 349.\n\n Sporangia, 244.\n\n Spores, 244.\n\n Sporozoa, 235.\n\n Sprouts, 36, 148, 151, 154, 165, 183.\n\n State and the individual, the, 409.\n\n States, modern, defects of, 409, 410.\n\n Stationary life in animals, 275.\n\n Stauraxonia, 175.\n\n Stimuli, acoustic, 311;\n action of, 295;\n chemical, 301-309;\n conduction of, 295, 396;\n electric, 312, 313;\n gravitational, 309-312;\n optic, 297-300;\n thermic, 299-302.\n\n Stock, the, 168, 184.\n\n Strauss, D. F., 72.\n\n Strophogenesis, 254.\n\n Substance, attributes of, 446, 448;\n eternity, of, 97;\n the problem of, 2.\n\n Suicide, contradictory views of, 112;\n occasional justice of, 112, 113, 116.\n\n Sun-dew, action of the, 304.\n\n Supernatural, the, 87, 88.\n\n Superstition, 56.\n\n Sutherland, A., on morality, 392.\n\n Swimming-bladder, the, 231.\n\n Symbiosis, 238.\n\n Symmetry, 171, 172.\n\n Sympathy, 115.\n\n\n Tailor theory, the, 383.\n\n Tape-worms, 237.\n\n Taste, 302, 303.\n\n Technical science, progress of, 465.\n\n Tectology, 94.\n\n Teleology, 181, 366.\n\n Teleology in movement, 265.\n\n Teleology, mechanical, 362, 363.\n\n Temperature, perception of, 299-301.\n\n Thallophyta, 161, 165.\n\n Thallus, the, 165, 195.\n\n Theology, 468.\n\n Thermotaxis, 301.\n\n Thigmotaxis, 310.\n\n Thought as attribute of substance, 445.\n\n Thought centres, 13, 329.\n\n Time, nature of, 70.\n\n Tissue animals, 163;\n plants, 162.\n\n Tissues, primary and secondary, 161, 162.\n\n Tocogony, 240.\n\n Touch, sense of, 309;\n in plants, 300, 310.\n\n Tracheata, the, 231.\n\n Tradition, power of, 423.\n\n Transgressive growth, 42, 44, 240, 241.\n\n Transubstantiation, 426.\n\n Treviranus, 79.\n\n Tropesis, 296, 308.\n\n Trophoplasts, 143.\n\n Truth, nature of, 1, 2, 4.\n\n T\u00fcbingen school, the, 72.\n\n Turgescence movements, 274, 275.\n\n Turgor, 273-275.\n\n Types of organic structure, 173-184.\n\n\n Unequal value of life, 390.\n\n\n Value of modern life, 408, 409.\n\n Variability in species, 373.\n\n Variation movements, 274.\n\n Veddahs, the, 393.\n\n Vegetal diet, 227.\n\n Vertebrates, mind in the, 328;\n motor apparatus of the, 283, 284;\n succession of the, 327.\n\n Verworn, Max. on enzyma, 46;\n on the nature of life, 28;\n on the origin of life, 348.\n\n Vibratory movement, 271.\n\n Virchow and evolution, 322;\n on the aim of science, 5.\n\n Vital force, the, 47-51.\n\n ---- movement, 266-286.\n\n Vitalism, 47-51, 459.\n\n Voluntary movement mechanical, 262-264.\n\n\n War, 400, 409.\n\n Watch compared with organism, 30.\n\n Water-feet, 280.\n\n Water-vessels, 230.\n\n Weismann on immortality, 90-101;\n on selection, 364;\n on the structure of plasm, 137.\n\n Will, freedom of the, 263, 265, 286.\n\n Wind-pipe, the, 232.\n\n Woman, improvement in position of, 402.\n\n\n Zehnder on the origin of life, 344.\n\n Ziegler on instinct, 418.\n\n Zoomonera, 193, 219.\n\n Zooplasm, 213.\n\n\n THE END\n\n\n\n\n FOOTNOTES:\n\n[1] The English translation met with almost equal success. Nearly\none hundred thousand copies of the cheap edition have already been\nsold.--TRANS.\n\n[2] Further particulars about the relations of the thought-centres to\nthe sense-centres will be found in the tenth chapter of _The Riddle of\nthe Universe_.\n\n[3] English readers who are acquainted with Romanes's posthumous\n_Thoughts on Religion_ will recognize the justice of this analysis.\nRomanes speaks expressly of the acceptance of Christianity entailing\n\"the sacrifice of his intellect.\"--TRANS.\n\n[4] This refers almost entirely to Germany. The reader will remember\nthat, when Lord Kelvin endeavored to make theosophic capital out\nof this temporary confusion in German science, he was immediately\nsilenced by the leading biologists of this country, Professor E.\nRay-Lankester (for zoology), Sir W. T. Thiselton-Dyer (for botany),\nand Sir J. Burdon-Sanderson (for physiology), who sharply rejected\nvitalism.--TRANS.\n\n[5] The German word _wunder_ corresponds equally to the English\n\"miracle\" and \"wonder.\" It has seemed necessary to translate it\n\"wonder\" in the title of the work, but frequently as \"miracle\" in this\nchapter.--TRANS.\n\n[6] The English reader may usefully be reminded that Professor Loofs,\nHaeckel's chief critic, and one of the foremost German theologians,\nrejects these articles of the Creed no less than Haeckel does. A glance\nat the pertinent articles in the _Encyclop\u00e6dia Biblica_ will show how\nwidely theologians now discard these beliefs.--TRANS.\n\n[7] Compare the opinion of the distinguished American psychologist,\nM\u00fcnsterberg \"Science opposes to any doctrine of individual immortality\nan unbroken and impregnable barrier\" (_Psychology and Life_, p.\n85).--TRANS.\n\n[8] A translation of the latest edition of the _Anthropogenie_, with\nthe full number of fresh illustrations (thirty plates and five hundred\nand twelve wood-cuts), will be issued very shortly by the Rationalist\nPress Association, under the title of _The Evolution of Man_.\n\n[9] I may remind the English reader that the chosen ecclesiastical\nchampion against Haeckel in this country, the Rev. F. Ballard, made\nthis extraordinary fallacy the very pith of his \"scientific\" attack on\nmonism.--TRANS.\n\n[10] As already stated, it will presently appear in England with the\ntitle, _The Evolution of Man_.--TRANS.\n\n[11] At the moment I translate this, telegrams from Germany announce\nthat, by the emperor's orders, a number of ladies were excluded from\nthe opera for not observing this custom.--TRANS.\n\n[12] The English reader will find in this a reply to the foolish notion\nwhich has been circulated that the recent discovery of radioaction\nand the composition of the atom from electrons has affected Haeckel's\nposition. His monism is completely indifferent to changes in the\nphysicist conception of the nature of matter.--TRANS.\n\n\n\n\n TRANSCRIBER'S NOTES:\n\n--Obvious print and punctuation errors were corrected.\n\n--The large tables at pages 96 and 189 have been splitted into two parts.\n\n--Original work has \"CHAPTER I\" instead of \"CHAPTER VI\" at page 121.\n Corrected.\n\n--Original work does not have \"XI\" at the beginning of chapter (page 239).\n Added.","title":"The Wonders of Life: A Popular Study of Biological Philosophy","tradition":"philosophy-ethics","translated_text":null,"word_count":148788}