{"collection":"philosophy-ethics","full_text_available":true,"graph_url":"https://unchartedknowledge.5gfusion.net/v2/api/page/gutenberg_26438/graph","html_url":"https://unchartedknowledge.5gfusion.net/v2/page/gutenberg_26438","id":"gutenberg_26438","license":"Public Domain (US)","rights_basis":"gutenberg_metadata_copyright_false","source":"gutenberg","source_url":"https://www.gutenberg.org/ebooks/26438","summary":null,"tags":["Category: Philosophy & Ethics","Category: Science - Biology","Heredity","Variation (Biology)"],"text":"Produced by Bryan Ness, Stephen Blundell and the Online\nDistributed Proofreading Team at https://www.pgdp.net (This\nbook was produced from scanned images of public domain\nmaterial from the Google Print project.)\n\n\n\n\n\n\n\n\n\n _NATURE SERIES_\n\n\n               ARE THE EFFECTS OF USE AND\n                    DISUSE INHERITED?\n\n           _AN EXAMINATION OF THE VIEW HELD BY\n                   SPENCER AND DARWIN_\n\n\n                           BY\n                   WILLIAM PLATT BALL\n\n\n                         LONDON\n                    MACMILLAN AND CO.\n                      AND NEW YORK\n                          1890\n\n _The Right of Translation and Reproduction is Reserved_\n\n\n\n\n RICHARD CLAY AND SONS, LIMITED,\n       LONDON AND BUNGAY.\n\n\n\n\nPREFACE.\n\n\nMy warmest thanks are due to Mr. Francis Darwin, to Mr. E. B. Poulton\n(whose interest in the subject here discussed is shown by his share in\nthe translation of Weismann's _Essays on Heredity_), and to Professor\nRomanes, for the help afforded by their kindly suggestions and\ncriticisms, and for the advice and recommendation under which this essay\nis now published. Encouragement from Mr. Francis Darwin is to me the\nmore precious, and the more worthy of grateful recognition, from the\nfact that my general conclusion that acquired characters are _not_\ninherited is at variance with the opinion of his revered father, who\naided his great theory by the retention of some remains of Lamarck's\ndoctrine of the inherited effect of habit. I feel as if the son, as\nrepresentative of his great progenitor, were carrying out the idea of an\nappreciative editor who writes to me: \"We must say that if Darwin were\nstill alive, he would find your arguments of great weight, and\nundoubtedly would give to them the serious consideration which they\ndeserve.\" I hope, then, that I may be acquitted of undue presumption in\nopposing a view sanctioned by the author of the _Origin of Species_, but\nalready stoutly questioned and firmly rejected by such followers of his\nas Weismann, Wallace, Poulton, Ray Lankester, and others, to say nothing\nof its practical rejection by so great an authority on heredity as\nFrancis Galton.\n\nThe sociological importance of the subject has already been insisted on\nin emphatic terms by Mr. Herbert Spencer, and this importance may be\neven greater than he imagined.\n\nCivilization largely sets aside the harsh but ultimately salutary action\nof the great law of Natural Selection without providing an efficient\nsubstitute for preventing degeneracy. The substitute on which moralists\nand legislators rely--if they think on the matter at all--is the\ncumulative inheritance of the beneficial effects of education, training,\nhabits, institutions, and so forth--the inheritance, in short, of\nacquired characters, or of the effects of use and disuse. If this\nsubstitute is but a broken reed, then the deeper thinkers who gradually\nteach the teachers of the people, and ultimately even influence the\nlegislators and moralists, must found their systems of morality and\ntheir criticisms of social and political laws and institutions and\ncustoms and ideas on the basis of the Darwinian law rather than on that\nof Lamarck.\n\nLooking forward to the hope that the human race may become consciously\nand increasingly master of itself and of its destiny, and recognizing\nthe Darwinian principle of the selection of the fittest as the _only_\nmeans of preventing the moral and physical degeneracy which, like an\ninternal dry rot, has hitherto been the besetting danger of all\ncivilizations, I desire that the thinkers who mould the opinions of\nmankind shall not be led astray from the true path of enduring progress\nand happiness by reliance on fallacious beliefs which will not bear\nexamination. Such, at least, is the feeling or motive which has prompted\nme to devote much time and thought to a difficult but important inquiry\nin a debatable region of inference and conjecture, where (I am afraid)\nevidence on either side can never be absolutely conclusive, and where,\nespecially, the absolute demonstration of a universal negative cannot\nreasonably be expected.\n\n\n\n\nCONTENTS.\n\n\n                                                                PAGE\n PREFACE                                                           v\n\n IMPORTANCE AND BEARING OF THE INQUIRY                             1\n\n SPENCER'S EXAMPLES AND ARGUMENTS                               6-44\n   DIMINUTION OF THE JAWS                                          6\n   DIMINISHED BITING MUSCLES OF LAP-DOGS                          12\n   CROWDED TEETH                                                  14\n   BLIND CAVE-CRABS                                               17\n   NO CONCOMITANT VARIATION FROM CONCOMITANT DISUSE               17\n   THE GIRAFFE, AND NECESSITY FOR CONCOMITANT VARIATION           18\n   ALLEGED RUINOUS EFFECTS OF NATURAL SELECTION                   23\n   ADVERSE CASE OF NEUTER INSECTS                                 24\n   AESTHETIC FACULTIES                                             29\n   LACK OF EVIDENCE                                               34\n   INHERITED EPILEPSY IN GUINEA-PIGS                              35\n   INHERITED INSANITY AND NERVOUS DISORDERS                       36\n   INDIVIDUAL AND TRANSMISSIBLE TYPE NOT MODIFIED ALIKE           40\n\n DARWIN'S EXAMPLES                                            45-100\n   REDUCED WINGS OF BIRDS OF OCEANIC ISLANDS                      49\n   DROOPING EARS AND DETERIORATED INSTINCTS                       53\n   WINGS AND LEGS OF DUCKS AND FOWLS                              55\n   PIGEONS' WINGS                                                 62\n   SHORTENED BREAST-BONE IN PIGEONS                               64\n   SHORTENED FEET IN PIGEONS                                      70\n   SHORTENED LEGS OF RABBITS                                      70\n   BLIND CAVE-ANIMALS                                             72\n   INHERITED HABITS                                               73\n   TAMENESS OF RABBITS                                            76\n   MODIFICATIONS OBVIOUSLY ATTRIBUTABLE TO SELECTION              82\n   SIMILAR EFFECTS OF NATURAL SELECTION AND USE-INHERITANCE       83\n   INFERIORITY OF SENSES IN EUROPEANS                             85\n   SHORT-SIGHT IN WATCHMAKERS AND ENGRAVERS                       85\n   LARGER HANDS OF LABOURERS' INFANTS                             87\n   THICKENED SOLE IN INFANTS                                      88\n   A SOURCE OF MENTAL CONFUSION                                   91\n   WEAKNESS OF USE-INHERITANCE                                    94\n\n INHERITED INJURIES                                          101-118\n   INHERITED MUTILATIONS                                         101\n   THE MOTMOT'S TAIL                                             110\n   OTHER INHERITED INJURIES MENTIONED BY DARWIN                  111\n   QUASI-INHERITANCE                                             116\n\n MISCELLANEOUS CONSIDERATIONS                                119-143\n   TRUE RELATION OF PARENTS AND OFFSPRING                        119\n   INVERSE INHERITANCE                                           123\n   EARLY ORIGIN OF THE OVA                                       124\n   MARKED EFFECTS OF USE AND DISUSE ON THE INDIVIDUAL            126\n   WOULD NATURAL SELECTION FAVOUR USE-INHERITANCE?               127\n   USE-INHERITANCE AN EVIL                                       128\n   VARIED EFFECTS OF USE AND DISUSE                              134\n   USE-INHERITANCE IMPLIES PANGENESIS                            137\n   PANGENESIS IMPROBABLE                                         138\n   SPENCER'S EXPLANATION OF USE-INHERITANCE                      141\n\n CONCLUSIONS                                                 144-156\n   USE-INHERITANCE DISCREDITED AS UNNECESSARY, UNPROVEN,\n       AND IMPROBABLE                                            144\n   MODERN RELIANCE ON USE-INHERITANCE MISPLACED                  145\n\n\n\n\nARE THE EFFECTS OF USE AND DISUSE INHERITED?\n\n\n\n\nIMPORTANCE AND BEARING OF THE INQUIRY.\n\n\nThe question whether the effects of use and disuse are inherited, or, in\nother words, whether acquired characters are hereditary, is of\nconsiderable interest to the general student of evolution; but it is, or\nshould be, a matter of far deeper interest to the thoughtful\nphilanthropist who desires to ensure the permanent welfare and happiness\nof the human race. So profoundly important, in fact, are the moral,\nsocial, and political conclusions that depend on the answer to this\ninquiry, that, as Mr. Herbert Spencer rightly says, it \"demands, beyond\nall other questions whatsoever, the attention of scientific men.\"\n\nIt is obvious that we can produce important changes in the individual.\nWe can, for example, improve his muscles by athletics, and his brain by\neducation. The use of organs enlarges and strengthens them; the disuse\nof parts or faculties weakens them. And so great is the power of habit\nthat it is proverbially spoken of as \"second nature.\" It is thus certain\nthat we can modify the individual. We can strengthen (or weaken) his\nbody; we can improve (or deteriorate) his intellect, his habits, his\nmorals. But there remains the still more important question which we are\nabout to consider. Will such modifications be inherited by the offspring\nof the modified individual? Does individual improvement transmit itself\nto descendants independently of personal teaching and example? Have\nartificially produced changes of structure or habit any inherent\ntendency to become congenitally transmissible and to be converted in\ntime into fixed traits of constitution or character? Can the\nphilanthropist rely on such a tendency as a hopeful factor in the\nevolution of mankind?--the only sound and stable basis of a higher and\nhappier state of things being, as he knows or ought to know, the innate\nand constitutionally-fixed improvement of the race as a whole. If\nacquired modifications are impressed on the offspring and on the race,\nthe systematic moral training of individuals will in time produce a\nconstitutionally moral race, and we may hope to improve mankind even in\ndefiance of the unnatural selection by which a spurious but highly\npopular philanthropy would systematically favour the survival of the\nunfittest and the rapid multiplication of the worst. But if acquired\nmodifications do not tend to be transmitted, if the use or disuse of\norgans or faculties does not similarly affect posterity by inheritance,\nthen it is evident that no innate improvement in the race can take place\nwithout the aid of natural or artificial selection.\n\nHerbert Spencer maintains that the effects of use and disuse _are_\ninherited in kind, and in his _Factors of Organic Evolution_[1] he has\nsupported his contention with a selection of facts and reasonings which\nI shall have the temerity to examine and criticize. Darwin also held the\nsame view, though not so strongly. And here, to prevent\nmisunderstanding, I may say that the admiration and reverence and\ngratitude due to Darwin ought not to be allowed to interfere in the\nslightest degree with the freest criticism of his conclusions. To\nperfect his work by the correction of really extraneous errors is as\nmuch a sacred duty as to study and apply the great truths he has taught.\n\n\nFOOTNOTES:\n\n[1] Which originally appeared in the _Nineteenth Century_ for April and\nMay, 1886.\n\n\n\n\nSPENCER'S EXAMPLES AND ARGUMENTS.\n\n\nDIMINUTION OF THE JAWS IN CIVILIZED RACES.\n\nMr. Spencer verified this by comparing English jaws with Australian and\nNegro jaws at the College of Surgeons.[2] He maintains that the\ndiminution of the jaw in civilized races can _only_ have been brought\nabout by inheritance of the effects of lessened use. But if English jaws\nare lighter and thinner than those of Australians and Negroes, so too is\nthe rest of the skull. As the diminution in the weight and thickness of\nthe walls of the cranium cannot well be ascribed to disuse, it must be\nattributed to some other cause; and this cause may have affected the jaw\nalso. Cessation of the process by which natural selection[3] favoured\nstrong thick bones during ages of brutal violence might bring about a\nchange in this direction. Lightness of structure, facilitating agility\nand being economical of material, would also be favoured by natural\nselection so far as strength was not too seriously diminished.\n\nSexual selection powerfully affects the human face, and so must affect\nthe jaws--as is shown by the differences between male and female jaws,\nand by the relative lightness and smallness of the latter, especially in\nthe higher races. Human preference, both sexual and social, would tend\nto eliminate huge jaws and ferocious teeth when these were no longer\nneeded as weapons of war or organs of prehension, &c. We can hardly\nassume that the lower half of the face is specially exempt from the\ninfluence of natural and sexual selection; and the effects of these\nundoubted factors of evolution must be fully considered before we are\nentitled to call in the aid of a factor whose existence is questioned.\n\nAfter allowing for lost teeth and the consequent alveolar absorption,\nand for a reduction proportional to that shown in the rest of the skull,\nthe difference in average weight in fifty European and fourteen\nAustralian male jaws at the College of Surgeons turned out to be less\nthan a fifth of an ounce, or about 5 per cent. This slight reduction may\nbe much more than accounted for by such causes as disuse in the\nindividual, human preference setting back the teeth, and partial\ntransference of the much more marked diminution seen in female jaws.\nThere is apparently no room for accumulated _inherited_ effects of\nancestral disuse. The number of jaws is small, indeed; but weighing them\nis at least more decisive than Mr. Spencer's mere inspection.\n\nThe differences between Anglo-Saxon male jaws and Australian and\nTasmanian jaws are most easily explained as effects of human preference\nand natural selection. We can hardly suppose that disuse would maintain\nor develop the projecting chin, increase its perpendicular height till\nthe jaw is deepest and strongest at its extremity, evolve a side flange,\nand enlarge the upper jaw-bone to form part of a more prominent nose,\nwhile drawing back the savagely obtrusive teeth and lips to a more\npleasing and subdued position of retirement and of humanized beauty. If\nhuman preference and natural selection caused some of these differences,\nwhy are they incompetent to effect changes in the direction of a\ndiminution of the jaw or teeth? And if use and disuse are the sole\nmodifying agents in the case of the human jaw, why should men have any\nmore chin than a gorilla or a dog?\n\nThe excessive weight of the West African jaws at the College of Surgeons\nis partly _against_ Mr. Spencer's contention, unless he assumes that\nGuinea Negroes use their jaws far more than the Australians, a\nsupposition which seems extremely improbable. The heavier skull and\nnarrower molar teeth point however to other factors than increased use.\n\nThe striking variability of the human jaw is strongly opposed to the\nidea of its being under the direct and dominant control of so uniform a\ncause as ancestral use and disuse. Mr. Spencer regards a variation of 1\noz. as a large one, but I found that the English jaws in the College of\nSurgeons varied from 1.9 oz. to 4.3 oz. (or 5 oz. if lost teeth were\nallowed for); Australian jaws varied from 2 oz. to 4.5 oz. (with _no_\nlost teeth to allow for); while in Negro jaws the maximum rose to over\n5-1/2 oz.[4] In spite of disuse some European jaws were twice as heavy\nas the lightest Australian jaw, either absolutely or (in some cases)\nrelatively to the cranium. The uniformity of change relied upon by Mr.\nSpencer is scarcely borne out by the facts so far as male jaws are\nconcerned. The great reduction in the weight of _female_ jaws _and\nskulls_ evidently points to sexual selection and to panmixia under male\nprotection.\n\nI think, on the whole, we must conclude that the human jaws do not\nafford satisfactory proof of the inheritance of the effects of use and\ndisuse, inasmuch as the differences in their weight and shape and size\ncan be more reasonably and consistently accounted for as the result of\nless disputable causes.\n\n\nDIMINISHED BITING MUSCLES OF LAP-DOGS.\n\nThe next example, the reduced biting muscles, &c., of lap-dogs is also\nunsatisfactory as a proof of the inheritance of the effects of disuse;\nfor the change can readily be accounted for without the introduction of\nsuch a factor. The previous natural selection of strong jaws and teeth\nand muscles is reversed. The conscious or unconscious selection of\nlap-dogs with the least tendency to bite would easily bring about a\ngeneral enfeeblement of the whole biting apparatus--weakness of the\nparts concerned favouring harmlessness. Mr. Spencer maintains that the\ndwindling of the parts concerned in clenching the jaw is certainly not\ndue to artificial selection because the modifications offer no\nappreciable external signs. Surely hard biting is sufficiently\nappreciable by the person bitten without any visual admeasurement of the\nmasseter muscles or the zygomatic arches. Disuse during lifetime would\nalso cause some amount of degeneracy; and I am not sure that Mr. Spencer\nis right in _entirely_ excluding economy of nutrition from the problem.\nBreeders would not over-feed these dogs; and the puppies that grew most\nrapidly would usually be favoured.\n\n\nCROWDED TEETH.\n\nThe too closely-packed teeth in the \"decreasing\" jaws of modern men (p.\n13)[5] are also suggestive of other causes than use and disuse. Why is\nthere not simultaneous variation in teeth and jaws, if disuse is the\ngoverning factor? Are we to suppose that the size of the human teeth is\nmaintained by use at the same time that the jaws are being diminished by\ndisuse? Mr. Spencer acknowledges that the crowding of bull-dogs' and\nlap-dogs' teeth is caused by the artificial selection of shortened jaws.\nIf a similar change is really occurring in man, could it not be\nsimilarly explained by some factor, such as sexual selection, which\nmight affect the outward appearance at the cost of less obvious defects\nor inconveniences?\n\nMr. Spencer points to the decay of modern teeth as a sign or result of\ntheir being overcrowded through the diminution of the jaw by disuse.[6]\nBut the teeth which are the most frequently overcrowded are the lower\nincisors. The upper incisors are less overcrowded, being commonly\npressed outwards by the lower arc of teeth fitting inside them in\nbiting. The lower incisors are correspondingly pressed inwards and\ncloser together. Yet the upper incisors decay--or at least are\nextracted--about twenty times as frequently as the closely packed lower\nincisors.[7] Surely this must indicate that the cause of decay is not\novercrowding.\n\nThe lateness and irregularity of the wisdom teeth are sometimes\nsupposed to indicate their gradual disappearance through want of room in\na diminishing jaw. But a note on Tasmanian skulls in the _Catalogue of\nthe College of Surgeons_ (p. 199) shows that this lateness and\nirregularity have been common among Tasmanians as well as among\ncivilized races, so that the change can hardly be attributed to the\neffects of disuse under civilization.\n\n\nBLIND CAVE-CRABS.\n\nThe cave-crabs which have lost their disused eyes but _not the disused\neye-stalks_ appear to illustrate the effects of natural selection rather\nthan of disuse. The loss of the exposed, sensitive, and\nworse-than-useless eye, would be a decided gain, while the disused\neye-stalk, being no particular detriment to the crab, would be but\nslightly affected by natural selection, though open to the cumulative\neffects of disuse. The disused but better protected eyes of the blind\ncave-rat are still \"of large size\" (_Origin of Species_, p. 110).\n\n\nNO CONCOMITANT VARIATION FROM CONCOMITANT DISUSE.\n\nIt is but fair to add that these instances of the cave-crab's eye-stalk\nand the closely-packed teeth are put forward by Mr. Spencer with the\nmore immediate object of proving that there is \"no concomitant\nvariation in co-operative parts,\" even when \"formed out of the same\ntissue, like the crab's eye and its peduncle\" (pp. 12-14, 23, 33). It\nescapes his notice, however, that in two out of his three cases it is\n_disuse_, or _diminished use_, which fails to cause concomitant\nvariation or proportionate variation.\n\n\nTHE GIRAFFE, AND NECESSITY FOR CONCOMITANT VARIATION.\n\nHaving unwittingly shown that lessened use of closely-connected and\nco-operative parts does not cause concomitant variation in these parts,\nMr. Spencer concludes that the concomitant variation requisite for\nevolution can only be caused by altered degrees of use or disuse. He\nelaborately argues that the many co-ordinated modifications of parts\nnecessitated by each important alteration in an animal are so complex\nthat they cannot possibly be brought about except by the inherited\neffect of the use and disuse of the various parts concerned. He holds,\nfor instance, that natural selection is inadequate to effect the\nnumerous concomitant changes necessitated by such developments as that\nof the long neck of the giraffe. Darwin, however, on the contrary, holds\nthat natural selection alone \"would have sufficed for the production of\nthis remarkable quadruped.\"[8] He is surprised at Mr. Spencer's view\nthat natural selection can do so little in modifying the higher animals.\nThus one of the chief arguments with which Mr. Spencer supports his\ntheory is so poorly founded as to be rejected by a far greater authority\non such subjects. All that is needed is that natural selection should\npreserve the tallest giraffes through times of famine by their being\nable to reach otherwise inaccessible stores of foliage. The continual\nvariability of all parts of the higher animals gives scope for\ninnumerable changes, and Nature is not in a hurry. Mr. Spencer, however,\nsays that \"the chances against any adequate readjustments fortuitously\narising must be infinity to one.\" But he has also shown that altered\ndegree of use does not cause the needed concomitant variation of\nco-operative parts. So the chances against a beneficial change in an\nanimal must be, at a liberal estimate, infinity to two. Mr. Spencer, if\nhe has proved anything, has proved that it is practically impossible\nthat the giraffe can have acquired a long neck, or the elk its huge\nhorns, or that any species has ever acquired any important modification.\n\nMr. Wallace, in his _Darwinism_, answers Mr. Spencer by a collection of\nfacts showing that \"variation is the rule,\" that the range of variation\nin wild animals and plants is much greater than was supposed, and that\n\"each part varies to a considerable extent independently\" of other\nparts, so that \"the materials constantly ready for natural selection to\nact upon are abundant in quantity and very varied in kind.\" While\nco-operative parts would often be more or less correlated, so that they\nwould tend to vary together, coincident variation is not necessary. The\nlengthened wing might be gained in one generation, and the strengthened\nmuscle at a subsequent period; the bird in the meanwhile drawing upon\nits surplus energy, aided (as I would suggest) by the strengthening\neffect of increased use in the individual. Seeing that artificial\nselection of complicated variations has modified animals in many points\neither simultaneously or by slow steps, as with otter-sheep, fancy\npigeons, &c. (many of the characters thus obtained being clearly\nindependent of use and disuse), natural selection must be credited with\nsimilar powers, and Mr. Wallace concludes that Mr. Spencer's\ninsuperable difficulty is \"wholly imaginary.\"\n\nThe extract concerning a somewhat similar \"class of difficulties,\" which\nMr. Spencer quotes from his _Principles of Biology_, is faulty in its\nreasoning,[9] though legitimate in its conclusion concerning the\nincreasing difficulty of evolution in proportion with the increasing\nnumber and complexity of faculties to be evolved. But this increasing\ndifficulty of complex evolution is only overcome by _some_\nfavourably-varying individuals and species--not by all. And as the\ndifficulty increases we find neglect and decay of the less-needed\nfaculties--as with domesticated animals and civilized men, who lose in\none direction while they gain in another. The increasing difficulty of\ncomplex evolution by natural selection is no proof whatever of\nuse-inheritance[10] except to those who confound difficulty with\nimpossibility.\n\n\nALLEGED RUINOUS EFFECTS OF NATURAL SELECTION.\n\nMr. Spencer further contends that natural selection, by unduly\ndeveloping specially advantageous modifications without the necessary\nbut complex secondary modifications, would render the constitution of a\nvariety \"unworkable\" (p. 23). But this seems hardly feasible, seeing\nthat natural selection must continually favour the most workable\nconstitutions, and will only preserve organisms in proportion as they\ncombine general workableness with the special modification. On the other\nhand, according to Mr. Spencer himself, use-inheritance must often\ndisturb the balance of the constitution. Thus it tends to make the jaws\nand teeth unworkable through the overcrowding and decay of the\nteeth--there being, as his illustrations show, no simultaneous or\nconcomitant or proportional variation in relation to altered degree of\nuse or disuse.\n\n\nADVERSE CASE OF NEUTER INSECTS.\n\nMr. Spencer also holds that most mental phenomena, especially where\ncomplex or social or moral, can only be explained as arising from\nuse-inheritance, which becomes more and more important as a factor of\nevolution as we advance from the vegetable world and the lower grades of\nanimal life to the more complex activities, tastes, and habits of the\nhigher organizations (preface, and p. 74). But there happens to be a\ntolerably clear proof that such changes as the evolution of complicated\nstructures and habits and social instincts _can_ take place\nindependently of use-inheritance. The wonderful instincts of the working\nbees have apparently been evolved (at least in all their later social\ncomplications and developments) without the aid of use-inheritance--nay,\nin spite of its utmost opposition. Working bees, being infertile\n\"neuters,\" cannot as a rule transmit their own modifications and habits.\nThey are descended from countless generations of queen bees and drones,\nwhose habits have been widely different from those of the workers, and\nwhose structures are dissimilar in various respects. In many species of\nants there are two, and in the leaf-cutting ants of Brazil there are\n_three_, kinds of neuters which differ from each other and from their\nmale and female ancestors \"to an almost incredible degree.\"[11] The\nsoldier caste is distinguished from the workers by enormously large\nheads, very powerful mandibles, and \"extraordinarily different\"\ninstincts. In the driver ant of West Africa one kind of neuter is three\ntimes the size of the other, and has jaws nearly five times as long. In\nanother case \"the workers of one caste alone carry a wonderful sort of\nshield on their heads.\" One of the three neuter classes in the\nleaf-cutting ants has a single eye in the midst of its forehead. In\ncertain Mexican and Australian ants some of the neuters have huge\nspherical abdomens, which serve as living reservoirs of honey for the\nuse of the community. In the equally wonderful case of the termites, or\nso-called \"white ants\" (which belong, however, to an entirely different\norder of insect from the ants and bees) the neuters are blind and\nwingless, and are divided into soldiers and workers, each class\npossessing the requisite instincts and structures adapting it for its\ntasks. Seeing that natural selection can form and maintain the various\nstructures and the exceedingly complicated instincts of ants and bees\nand wasps and termites in direct defiance of the alleged tendency to\nuse-inheritance, surely we may believe that natural selection,\nunopposed by use-inheritance, is equally competent for the work of\ncomplex or social or mental evolution in the many cases where the strong\npresumptive evidence cannot be rendered almost indisputable by the\nexceptional exclusion of the modified animal from the work of\nreproduction.\n\nAnts and bees seem to be capable of altering their habits and methods of\naction much as men do. Bees taken to Australia cease to store honey\nafter a few years' experience of the mild winters. Whole communities of\nbees sometimes take to theft, and live by plundering hives, first\nkilling the queen to create dismay among the workers. Slave ants attend\ndevotedly to their captors, and fight against their own species. Forel\nreared an artificial ant-colony made up of five different and more or\nless hostile species. Why cannot a much more intelligent animal modify\nhis habits far more rapidly and comprehensively without the aid of a\nfactor which is clearly unnecessary in the case of the more intelligent\nof the social insects?\n\n\nAESTHETIC FACULTIES.\n\nThe modern development of music and harmony (p. 19) is undeniable, but\nwhy could it only have been brought about by the help of the inheritance\nof the effects of use? Why are we to suppose that \"minor traits\" such as\nthe \"aesthetic perceptions\" cannot have been evolved by natural selection\n(p. 20) or by sexual selection? Darwin holds that our musical faculties\nwere developed by sexual preference long before the acquisition of\nspeech. He believes that the \"rhythms and cadences of oratory are\nderived from previously developed musical powers\"--a conclusion \"exactly\nopposite\" to that arrived at by Mr. Spencer.[12] The emotional\nsusceptibility to music, and the delicate perceptions needed for the\nhigher branches of art, were apparently the work of natural and sexual\nselection in the long past. Civilization, with its leisure and wealth\nand accumulated knowledge, perfects human faculties by artificial\ncultivation, develops and combines means of enjoyment, and discovers\nunsuspected sources of interest and pleasure. The sense of harmony,\nmodern as it seems to be, must have been a latent and indirect\nconsequence of the development of the sense of hearing and of melody.\nUse, at least, could never have called it into existence. Nature favours\nand develops enjoyments to a certain extent, for they subserve\nself-preservation and sexual and social preference in innumerable ways.\nBut modern aesthetic advance seems to be almost entirely due to the\nculture of latent abilities, the formation of complex associations, the\nselection and encouragement of talent, and the wide diffusion and\nimitation of the accumulated products of the well-cultivated genius of\nfavourably varying individuals. The fact that uneducated persons do not\nenjoy the higher tastes, and the rapidity with which such tastes are\nacquired or professed, ought to be sufficient proof that modern culture\nis brought about by far swifter and more potent influences than\nuse-inheritance. Neither would this hypothetical factor of evolution\nmaterially aid in explaining the many other rapid changes of habit\nbrought about by education, custom, and the changed conditions of\ncivilization generally. Powerful tastes--as is incontestably shown in\nthe cases of alcohol and tobacco--lie latent for ages, and suddenly\nbecome manifest when suitable conditions arise. Every discovery, and\neach step in social and moral evolution, produces its wide-spreading\ntrain of consequences. I see no reason why use-inheritance need be\ncredited with any share in the cumulative results of the invention of\nprinting and the steam-engine and gunpowder, or of freedom and security\nunder representative government, or of science and art and the partial\nemancipation of the mind of man from superstition, or of the innumerable\nother improvements or changes that take place under modern civilization.\n\nMr. Spencer suggests an inquiry whether the greater powers possessed by\neminent musicians were not mainly due to the inherited effect of the\nmusical practice of their fathers (p. 19). But these great musicians\ninherited far more than their parents possessed. The excess of their\npowers beyond their parents' must surely be attributed to spontaneous\nvariation; and who shall say that the rest was in any way due to\nuse-inheritance? If, too, the superiority of geniuses proves\nuse-inheritance, why should not the inferiority of the sons of geniuses\nprove the existence of a tendency which is the exact opposite of\nuse-inheritance? But nobody collects facts concerning the degenerate\nbranches of musical families. Only the favourably varying branches are\nnoticed, and a general impression of rapid evolution of talent is thus\nproduced. Such cases might be explained, too, by the facts that musical\nfaculty is strong in both sexes, that musical families associate\ntogether, and that the more gifted members may intermarry. Great\nmusicians are often astonishingly precocious. Meyerbeer \"played\nbrilliantly\" at the age of six. Mozart played beautifully at four. Are\nwe to suppose that the effect of the _adult_ practice of parents was\ninherited at this early age? If use-inheritance was not necessary in the\ncase of Handel, whose father was a surgeon, why is it needed to account\nfor Bach?\n\n\nLACK OF EVIDENCE.\n\nThe \"direct proofs\" of use-inheritance are not as plentiful as might be\ndesired, it appears (pp. 24-28). This acknowledged \"lack of recognized\nevidence\" is indeed the weakest feature in the case, though Mr. Spencer\nwould fain attribute this lack of direct proof to insufficient\ninvestigation and to the inconspicuous nature of the inheritance of the\nmodification. But there is an almost endless abundance of conspicuous\nexamples of the effects of use and disuse in the individual. How is it\nthat the subsequent inheritance of these effects has not been more\nsatisfactorily observed and investigated? Horse-breeders and others\ncould profit by such a tendency, and one cannot help suspecting that the\nreason they ignore it must be its practical inefficacy, arising probably\nfrom its weakness, its obscurity and uncertainty or its non-existence.\n\n\nINHERITED EPILEPSY IN GUINEA-PIGS.\n\nBrown-Sequard's discovery that an epileptic tendency artificially\nproduced by mutilating the nervous system of a guinea-pig is\noccasionally inherited may be a fact of \"considerable weight,\" or on the\nother hand it may be entirely irrelevant. Cases of this kind strike one\nas peculiar exceptions rather than as examples of a general rule or law.\nThey seem to show that certain morbid conditions may occasionally affect\nboth the individual and the reproductive elements or transmissible type\nin a similar manner; but then we also know that such prompt and complete\ntransmission of an artificial modification is widely different from the\nusual rule. Exceptional cases require exceptional explanations, and are\nscarcely good examples of the effect of a general tendency which in\nalmost all other cases is so inconspicuous in its immediate effects.\nFurther remarks on this inherited epilepsy can be most conveniently\nintroduced later on in connection with Darwin's explanation of the\ninherited mutilation which it usually accompanies, but which Mr. Spencer\ndoes not mention.\n\n\nINHERITED INSANITY AND NERVOUS DISORDERS.\n\nMr. Spencer infers that, because insanity is usually hereditary, and\ninsanity can be artificially produced by various excesses, therefore\nthis artificially-produced insanity must also be hereditary (p. 28).\nDirect evidence of this conclusion would be better than a mere inference\nwhich may beg the very question at issue. That the liability to insanity\ncommonly runs in families is no proof that strictly non-inherited\ninsanity will subsequently become hereditary. I think that theories\nshould be based on facts rather than facts on theories, especially when\nthose facts are to be the basis or proof of a further theory.\n\nMr. Spencer also points out that he finds among physicians \"the belief\nthat nervous disorders of a less severe kind are inheritable\"--a general\nbelief which does not necessarily include the transmission of purely\nartificially-produced disorders, and so misses the point which is really\nat issue. He proceeds, however, to state more definitely that \"men who\nhave prostrated their nervous systems by prolonged overwork or in some\nother way, have children more or less prone to nervousness.\" The\nfollowing observations will, I think, warrant at least a suspension of\njudgment concerning this particular form of use-inheritance.\n\n(1) The nervousness is seen in the _children_ at an early age, although\nthe nervous prostration from which it is supposed to be derived\nobviously occurs in the parent at a much later period of life. This\nchange in time is contrary to the rule of inheritance at corresponding\nperiods; and, together with the unusual promptness and comparative\ncompleteness of the inheritance, it may indicate a special injury or\ndeterioration of the reproductive elements rather than true inheritance.\nThe healthy brain of early life has failed to transmit its robust\ncondition. Is use-inheritance, then, only effective for evil? Does it\nonly transfer the newly-acquired weakness, and not the previous\nlong-continued vigour?\n\n(2) Members of nervous families would be liable to suffer from nervous\nprostration, and by the ordinary law of heredity alone would transmit\nnervousness to their children.\n\n(3) The shattered nerves or insanity resulting from alcoholic and other\nexcesses, or from overwork or trouble, are evidently signs of a grave\nconstitutional injury which may react upon the reproductive elements\nnourished and developed in that ruined constitution. The deterioration\nin parent and child may often display itself in the same organs--those\nprobably which are hereditarily weakest. Acquired diseases or disorders\nthus appear to be transmitted, when all that was conveyed to the\noffspring was the exciting cause of a lowered vitality or disordered\naction, together with the ancestral liability to such diseases under\nsuch conditions.\n\n(4) Francis Galton says that \"it is hard to find evidence of the power\nof the personal structure to react upon the sexual elements, that is not\nopen to serious objection.\" Some of the cases of apparent inheritance he\nregards as coincidence of effect. Thus \"the fact that a drunkard will\noften have imbecile children, although his offspring previous to his\ntaking to drink were healthy,\" is an \"instance of simultaneous action,\"\nand not of true inheritance. \"The alcohol pervades his tissues, and, of\ncourse, affects the germinal matter in the sexual elements as much as it\ndoes that in his own structural cells, which have led to an alteration\nin the quality of his own nerves. Exactly the same must occur in the\ncase of many constitutional diseases that have been acquired by\nlong-continued irregular habits.\"[13]\n\n\nINDIVIDUAL AND TRANSMISSIBLE TYPE NOT MODIFIED ALIKE BY THE DIRECT\nEFFECT OF CHANGED HABITS OR CONDITIONS.\n\nMr. Spencer finds it hard to believe that the modifications conveyed to\noffspring are not identical in tendency with the changes effected in the\nparent by altered use or habit (pp. 23-25, 34). But it is perfectly\ncertain that the two sets of effects do not necessarily correspond. The\neffect of changed habits or conditions on the individual is often very\nfar from coinciding with the effects on the reproductive elements or\nthe transmissible type. The reproductive system is \"extremely\nsensitive\" to very slight changes, and is often powerfully affected by\ncircumstances which otherwise have little effect on the individual\n(_Origin of Species_, p. 7). Various animals and plants become sterile\nwhen domesticated or supplied with too much nourishment. The native\nTasmanians have already become extinct from sterility caused by greatly\nchanged diet and habits. If, as Mr. Spencer teaches, continued culture\nand brain-work will in time produce lessened fertility or comparative\nsterility, we may yet have to be careful that intellectual development\ndoes not become a species of suicide, and that the culture of the race\ndoes not mean its extinction--or at least the extinction of those most\nsusceptible of culture.\n\nThe reproductive elements are also disturbed and modified in innumerable\nminor ways. Changed conditions or habits tend to produce a general\n\"plasticity\" of type, the \"indefinite variability\" thus caused being\napparently irrelevant to the change, if any, in the individual.[14] A\nvast number of variations of structure have certainly arisen\nindependently of similar parental modification as the preliminary.\nWhatever first caused these \"spontaneous\" congenital variations affected\nthe reproductive elements quite differently from the individual. \"When a\nnew peculiarity first appears we can never predict whether it will be\ninherited.\" Many varieties of plants only keep true from shoots, and not\nfrom seed, which is by no means acted on in the same way as the\nindividual plant. Seeing that such plants have _two_ reproductive\ntypes, both constant, it is evident that these cannot both be modified\nin the same way as the parent is modified. Many parental modifications\nof structure and habit are certainly not conveyed to neuter ants and\nbees; other modifications, which are not seen in the parents, being\nconveyed instead. Many other circumstances tend to show that the\nindividual and the transmissible type are independent of each other so\nfar as modifications of parts are concerned.\n\nIt may seem natural to expect the transmission of an enlarged muscle or\na cultivated brain, but, on the other hand, why should it be\nunreasonable to expect that a modification which was non-congenital in\norigin should still remain non-congenital? Why should the\nnon-transmission of that which was not transmitted be surprising?\n\nMr. Spencer thinks that the non-transmission of acquired modifications\nis incongruous with the great fact of atavism. But the great law of the\ninheritance of that which is a development of the transmissible type\ndoes not necessarily imply the inheritance of modifications acquired by\nthe individual. Because English children may inherit blue eyes and\nflaxen hair from their Anglo-Saxon ancestors, it by no means follows\nthat an Englishman must inherit his father's sunburnt complexion or\nsmooth-shaven face. Of course atavism ultimately adopts many instances\nof revolt against its sway. But to assume that these changes of type\n_follow_ the personal change rather than cause it, is to assume the\nwhole question at issue. That like begets like is true as a broad\nprinciple, but it has many exceptions, and the non-heredity of acquired\ncharacters may be one of them.\n\n\nFOOTNOTES:\n\n[2] _Principles of Biology_, Sec. 166, footnote. The English jaws are\nsomewhat lighter than the Australian jaws, though I could not undertake\nto affirm that they are really shorter and smaller. In the typical\nskulls depicted on p. 68 of the official guide to the mammalian\ngalleries at South Kensington, the typical Caucasian jaw is very much\nlarger than the Tasmanian jaw, although the repulsively obtrusive teeth\nof the latter convey the contrary idea to the imagination. Mr. Spencer's\nassumption that the ancient Britons had large jaws appears to me\nerroneous. (See Professor Rolleston's _Scientific Papers and Addresses_,\ni. p. 250.)\n\n[3] Romanes, Galton, and Weismann have made great use of this principle\nin explaining the diminution of disused organs. Weismann has given it\nthe name of _Panmixia_,--_all_ individuals being equally free to survive\nand commingle their variations, and not merely selected or favoured\nindividuals. See his _Essays on Heredity_, &c., p. 90 (Clarendon Press).\n\n[4] Inclusive in each case of fixed strengthening wire weighing about a\nsixteenth of an ounce or less.\n\n[5] References of course are to _Factors of Organic Evolution_.\n\n[6] P. 13; and _Nineteenth Century_, February, 1888, p. 211.\n\n[7] Tomes's _Dental Surgery_, pp. 273-275. Tomes observes that it is as\nyet uncertain in what way civilization predisposes to caries. But he\nshows that caries is caused by the lime salts in the teeth being\nattacked by _acids_ from decomposing food in crevices, from artificial\ndrink such as cyder, from sugar, from medicine, and from vitiated\nsecretions of the mouth. It is evident that in civilized races natural\nselection cannot so rigorously insist on sound teeth, sound\nconstitutions, and _protective alkaline_ saliva. The reaction of the\ncivilized mouth is often acid, especially when the system is disordered\nby dyspepsia or other diseases or forms of ill-health common under\ncivilization. The main supply of saliva, which is poured from the cheeks\nopposite the upper molars, is often acid when in small quantities. But\nthe submaxillary and sub-lingual saliva poured out at the foot of the\nlower incisors and held in the front part of the jaw as in a spoon,\n\"differs from parotid saliva in being more alkaline\" (Foster's _Text\nBook of Physiology_, p. 238; Tomes, pp. 284, 685). One observer says\nthat the reaction near the lower incisors is \"never acid.\" Hence (I\nconclude) the remarkable immunity of the lower incisors and canines from\ndecay, an immunity which extends backwards in a lessening degree to the\nfirst and second bicuspids. The close packing of the lower incisors may\nassist by preventing the retention of decaying fragments of food. Sexual\nselection may promote caries by favouring white teeth, which are more\nprone to decay than yellow ones. Acid vitiation of the mucus might\naccount both for caries and (possibly) for the strange infertility of\nsome inferior races under civilization.\n\n[8] _Origin of Species_, pp. 198-9; _Variation of Animals and Plants\nunder Domestication_, vol. ii. p. 328 footnote, also p. 206.\n\n[9] Mr. Spencer weakly argues that an advantageous attribute (such as\nswiftness, keen sight, courage, sagacity, strength, &c.) cannot be\nincreased by natural selection unless it is \"of greater importance, for\nthe time being, than most of the other attributes\"; and that natural\nselection cannot develop any one superiority when animals are equally\npreserved by \"other superiorities.\" But as natural selection will\nsimultaneously eliminate tendencies to slowness, blindness, deafness,\nstupidity, &c., it _must_ favour and improve many points simultaneously,\nalthough no one of them may be of greater importance than the rest. Of\ncourse the more complicated the evolution the slower it will be; but\ntime is plentiful, and the amount of elimination is correspondingly\nvast.\n\n[10] I venture to coin this concise term to signify _the direct\ninheritance of the effects of use and disuse in kind_. Having a name for\na thing is highly convenient; it facilitates clearness and accuracy in\nreasoning, and in this particular inquiry it may save some confusion of\nthought from double or incomplete meanings in the shortened phrases\nwhich would otherwise have to be employed to indicate this great but\nnameless factor of evolution.\n\n[11] _Origin of Species_, pp. 230-232; Bates's _Naturalist on the\nAmazons_. Darwin is \"surprised that no one has hitherto advanced the\ndemonstrative case of neuter insects, against the well-known doctrine of\ninherited habit, as advanced by Lamarck.\" As he justly observes, \"it\nproves that with animals, as with plants, any amount of modification may\nbe effected by the accumulation of numerous, slight, spontaneous\nvariations, which are in any way profitable, without exercise or habit\nhaving been brought into play. For peculiar habits confined to the\nworkers or sterile females, however long they might be followed, could\nnot possibly affect the males and fertile females, which alone leave any\ndescendants.\" Some slight modification of these remarks, however, may\npossibly be needed to meet the case of \"factitious queens,\" who\n(probably through eating particles of the royal food) become capable of\nproducing a few male eggs.\n\n[12] _Descent of Man_, pp. 573, 572, and footnote.\n\n[13] _Contemporary Review_, December, 1875, p. 92.\n\n[14] See _Origin of Species_, pp. 5-8. \"Changed conditions induce an\nalmost indefinite amount of fluctuating variability, by which the whole\norganization is rendered in some degree plastic\" (_Descent of Man_, p.\n30). It also appears that \"the nature of the conditions is of\nsubordinate importance in comparison with the nature of the organism in\ndetermining each particular form of variation;--perhaps of not more\nimportance than the nature of the spark, by which a mass of combustible\nmatter is ignited, has in determining the nature of the flames\" (_Origin\nof Species_, p. 8).\n\n\n\n\nDARWIN'S EXAMPLES.\n\n\nThe most formidable cases brought forward by Mr. Spencer are from\nDarwin. I shall endeavour to show, however, that Darwin was probably\nwrong in retaining the older explanation of these facts, and that the\nremains of the Lamarckian theory of use-inheritance need not any longer\nencumber the great explanation which has superseded that fallacious and\nunproven theory and has rendered it totally unnecessary. Meanwhile I\nthink it is an excellent sign that Mr. Spencer has to complain that\n\"Nowadays most naturalists are more Darwinian than Mr. Darwin\nhimself\"--inasmuch as they are inclined to say that there is \"no proof\"\nthat the effects of use and disuse are inherited. Other excellent signs\nare the recent issue of a translation of Weismann's important essays on\nthis and kindred subjects,[15] the strong support given to his views by\nWallace in his _Darwinism_, and their adoption by Ray Lankester in his\narticle on Zoology in the latest edition of the _Encyclopaedia\nBritannica_. So sound and cautious an investigator as Francis Galton had\nalso in 1875 concluded that \"acquired modifications are barely, if at\nall, _inherited_, in the correct sense of that word.\"\n\nDarwin's belief in the inheritance of acquired characters was more or\nless hereditary in the family. His grandfather, Erasmus Darwin,\nanticipated Lamarck's views in his _Zoonomia_, which Darwin at one time\n\"greatly admired.\" His father was \"convinced\" of the \"inherited evil\neffects of alcohol,\" and to this extent at least he strongly impressed\nthe belief in the inheritance of acquired characters upon his\nchildren's minds.[16] Darwin must also have been imbued with Lamarckian\nideas from other sources, although Dr. Grant's enthusiastic advocacy\nentirely failed to convert him to a belief in evolution.[17]\n\"Nevertheless,\" he says, \"it is probable that the hearing rather early\nin life such views maintained and praised may have favoured my upholding\nthem under a different form in my _Origin of Species_\"--a remark which\nrefers to Lamarck's views on the general doctrine of evolution, but\nmight also prove equally true if applied to Darwin's partial retention\nof the Lamarckian explanation of that evolution. Professor Huxley has\npointed out that in Darwin's earlier sketch of his theory of evolution\n(1844) he attached more weight to the inheritance of acquired habits\nthan he does in his _Origin of Species_ published fifteen years\nlater.[18] He appears to have acquired the belief in early life without\nfirst questioning and rigorously testing it as he would have done had it\noriginated with himself. In later life it appeared to assist his theory\nof evolution in minor points, and in particular it appeared absolutely\nindispensable to him as the _only_ explanation of the diminution of\ndisused parts in cases where, as in domestic animals, economy of growth\nseemed to be practically powerless. He failed to adequately notice the\neffect of panmixia, or the withdrawal of selection, in causing or\nallowing degeneracy and dwindling under disuse; and he hardly attached\nsufficient importance to the fact that rudimentary organs and other\nsupposed effects of use or disuse are quite as marked features in\nneuter insects which cannot transmit the effects of use and disuse as\nthey are in the higher animals.\n\n\nREDUCED WINGS OF BIRDS OF OCEANIC ISLANDS.\n\nDarwin himself has pointed out that the rudimentary wings of island\nbeetles, at first thought to be due to disuse, are mainly brought about\nby natural selection--the best-winged beetles being most liable to be\nblown out to sea. But he says that in birds of the oceanic islands \"not\npersecuted by any enemies, the reduction of their wings has probably\nbeen caused by disuse.\" This explanation may be as fallacious as it is\nacknowledged to have been in the case of the island beetles. According\nto Darwin's own views, natural selection _must_ at least have played an\nimportant part in reducing the wings; for he holds that \"natural\nselection is continually trying to economize every part of the\norganization.\" He says: \"If under changed conditions of life a\nstructure, before useful, becomes less useful, its diminution will be\nfavoured, for it will profit the individual not to have its nutriment\nwasted in building up an useless structure.... Thus, as I believe,\nnatural selection will tend in the long run to reduce any part of the\norganization, as soon as it becomes, through changed habits,\nsuperfluous.\"[19] If, as Darwin powerfully urges (and he here ignores\nhis usual explanation), ostriches' wings are insufficient for flight in\nconsequence of the economy enforced by natural selection,[20] why may\nnot the reduced wings of the dodo, or the penguin, or the apteryx, or of\nthe Cursores generally, be wholly attributed to natural selection in\nfavour of economy of material and adaptation of parts to changed\nconditions? The great principle of economy is continually at work\nshaping organisms, as sculptors shape statues, by removing the\nsuperfluous parts; and a mere glance at the forms of animals in general\nwill show that it is well-nigh as dominant and universal a principle as\nis that of the positive development of useful parts. Other causes,\nmoreover besides actual economy, would favour shorter and more\nconvenient wings on oceanic islands. In the first place, birds that were\nsomewhat weak on the wing would be most likely to settle on an island\nand stay there. Shortened wings would then become advantageous because\nthey would restrain fatal migratory tendencies or useless and perilous\nflights in which the birds that flew furthest would be most often\ncarried away by storms and adverse winds. Reduced wings would keep the\nbirds near the shelter and the food afforded by the island and its\nneighbourhood, and in some cases would become adapted to act as fins or\nflappers for swimming under water in pursuit of fish.\n\nThe reduced size of the wings of these island birds is paralleled by the\nremarkable thinness, &c., of the shell of the \"gigantic land-tortoise\"\nof the Galapagos Islands. The changes seen in the carapace can hardly\nhave been brought about by the inherited effects of special disuse. Why\nthen should not the reduction of equally useless, more wasteful, and\nperhaps positively dangerous wings be also due to an economy which has\nbecome advantageous to bird and reptile alike through the absence of the\nmammalian rivals whose places they are evidently being modified to fill?\nThe _complete_ loss of the wings in neuter ants and termites can\nscarcely be due to the inherited effects of disuse; and as natural\nselection has abolished these wings in spite of the opposition of\nuse-inheritance, it must clearly be fully competent to reduce wings\nwithout its aid. In considering the rudimentary wings of the apteryx,\nor of the moa, emu, ostrich, &c., we must not forget the frequent or\noccasional occurrence of hard seasons, and times of drought and famine,\nwhen Nature eliminates redundant, wasteful, and ill-adapted organisms in\nso severe and wholesale a fashion. Where enemies are absent there would\nbe unrestrained multiplication, and this would greatly increase the\nseverity of the competition for food, and so hasten the elimination of\ndisused and useless parts.\n\n\nDROOPING EARS AND DETERIORATED INSTINCTS.\n\nMr. Galton has pointed out that existing races and existing organs are\nonly kept at their present high pitch of organic excellence by the\nstringent and incessant action of natural or artificial selection; and\nthe simple relaxation or withdrawal of such selective influences will\nalmost necessarily result in a certain amount of deterioration,\nindependently even of the principle of economy.[21] I think that this\ncessation of a previous selective process will account for the\ndrooping--but _not diminished_--ears of various domesticated animals\n(human preference and increased weight evidently aiding), and also for\nthe inferior instincts seen in them and in artificially-fed caterpillars\nof the silk-moth, which now \"often commit the strange mistake of\ndevouring the base of the leaf on which they are feeding, and\nconsequently fall down.\" Anyhow, I fail to see that anything is proved\nby this latter case, except that natural instinct may be perverted or\naborted under unnatural conditions and a changed method of selection\nwhich abolishes the powerful corrective formerly supplied by natural\nselection.\n\n\nWINGS AND LEGS OF DUCKS AND FOWLS.\n\nThe reduced wings and enlarged legs of domesticated ducks and fowls are\nattributed by Darwin and Spencer to the inheritance of the effects of\nuse and disuse. But the inference by no means follows. Natural selection\nwould usually favour these adaptive changes, and they would also have\nbeen aided by an artificial selection which is often unconscious or\nindirect. Birds with diminished power of flight would be less difficult\nto keep and manage, and in preserving and multiplying such birds man\nwould be unconsciously bringing about structural changes which would\neasily be regarded as effects of use and disuse. \"About eighteen\ncenturies ago Columella and Varro speak of the necessity of keeping\nducks in netted enclosures like other wild fowl, so that at this period\nthere was danger of their flying away.\"[22] Is it not probable that the\nbest fliers would escape most frequently, or would pine most if kept\nconfined? On the other hand, birds with lessened powers of flight would\nnot be eliminated as under natural conditions, but would be favoured;\nand natural selection, together with artificial selection of the most\nflourishing birds, would thicken and strengthen the legs to meet\nincreased demands upon them.\n\nThe diminution of the duck's wing is not great even in the birds that\n\"never fly,\" and from this we must deduct the direct effect of disuse on\nthe individual during its lifetime. As Weismann suggests, the\n_inherited_ portion of the change could only be ascertained by comparing\nthe bones, &c., of wild and tame ducks _similarly reared_. If individual\ndisuse diminished the weight of the duck's wing-bones by 9 per cent.\nthere would be nothing left to account for.\n\nI suspect that investigation would reveal anomalies inconsistent with\nthe theory of use-inheritance. Thus according to Darwin's tables of\ncomparative weights and measurements[23] the leg-bones of the Penguin\nduck have slightly diminished in length, although they have increased 39\nper cent. in weight. Relatively to the weight of the skeleton, the\nleg-bones have shortened in the tame breeds of ducks by over 5 per cent.\n(and in two breeds by over 8 per cent.) although they have increased\nmore than 28 per cent. in proportional weight.[24] How can increased use\nsimultaneously shorten and thicken these bones? If the relative\nshortening is attributed to a heavier skeleton, then the apparently\nreduced weight of the wing-bones is fully accounted for by the same\ncircumstance, and disuse has had no inherited effect.\n\nAnother strange circumstance is that the wing-bones have diminished _in\nlength only_. The shortening is about 6 per cent. more than in the\nshortened legs, and it amounts to 11 per cent. as compared with the\nweight of the skeleton. Such a shortening should represent a reduction\nof 29 per cent. in weight, whereas the actual reduction in the weight of\nthe wing-bones relatively to the weight of the skeleton is only 9 per\ncent. even in the breeds that never fly. Independently of shortening,\nthe disused wing-bones have actually thickened or increased in weight.\nIn the Aylesbury duck the disproportion caused by these conflicting\nchanges is so great that the wing-bones are 47 per cent. heavier than\nthey should be if their weight had varied proportionally with their\nlength.[25] The reduction in weight on which Darwin relies seems to be\nentirely due to the shortening, and this shortening appears to be\nirrelevant to disuse, since the wings of the Call duck are similarly\nshortened in their proportions by 12 per cent., although this bird\nhabitually flies to such an extent that Darwin partly attributes the\ngreatly increased weight of its wing-bones to increased use under\ndomestication.\n\nWe find that _all_ the changes are in the direction of shorter and\nthicker bones--a tendency which must be largely dependent upon the\nsuspension of the rigorous elimination which keeps the bones of the\nwild duck _long and light_. The used leg-bones and the disused\nwing-bones have alike been shortened and thickened, though in different\nproportions. Natural or artificial selection might easily thicken legs\nwithout lengthening them, or shorten wings without eliminating strong\nheavy bones, but it can hardly be contended that use-inheritance has\nacted in such conflicting ways. The thickening of the wing-bones has\nactually more than kept pace with any increase of weight in the\nskeleton, in spite of the effect of individual disuse and of the alleged\ncumulative effect of ancestral disuse for hundreds of generations. The\ncase of the duck deserves special attention as a crucial one, if only\nfrom the fact that in this instance, and in this instance only, has\nDarwin given the weights of the skeletons, thus furnishing the means for\na closer examination of his details than is usually possible.\n\nIf we ignore such factors as selection, panmixia, correlation, and the\neffects of use and disuse during lifetime, and still regard the case of\nthe domestic duck as a valid proof of the inheritance of the effects of\nuse and disuse, we must also accept it as an equally valid proof that\nthe effects of use and disuse are _not_ inherited. Nay, we may even have\nto admit that, in two points out of four, the _inherited_ effect of use\nand disuse on successive generations is exactly opposite to the\nimmediate effect on the individual.\n\nAmong fowls the wing-bones have lost much in weight but little or\nnothing in length--which is the reverse of what has occurred in ducks,\nalthough disuse is alleged to be the common cause in both cases. Some of\nthe fowls which fly least have their wing-bones as long as ever. In the\ncase of the Silk and Frizzled fowls--ancient breeds which \"cannot fly at\nall\"--and in that of the Cochins, which \"can hardly fly up to a low\nperch,\" Darwin observes \"how truly the proportions of an organ may be\ninherited although not fully exercised during many generations.\"[26] In\nfour out of twelve breeds the wing-bones had become slightly heavier\nrelatively to the leg-bones. Do not these facts tend to show that the\nchanges in fowls' wings are due to fluctuating variability and selective\ninfluences rather than to a general law whereby the effects of disuse\nare cumulatively inherited?\n\n\nPIGEONS' WINGS.\n\nConcerning pigeons' wings Darwin says: \"As fancy pigeons are generally\nconfined in aviaries of moderate size, and as even when not confined\nthey do not search for their own food, they must during many generations\nhave used their wings incomparably less than the wild rock-pigeon ...\nbut when we turn to the wings we find what at first appears a wholly\ndifferent and unexpected result.\"[27] This unexpected increase in the\nspread of the wings from tip to tip is due to the feathers, which have\nlengthened in spite of disuse. Excluding the feathers, the wings were\nshorter in seventeen instances, and longer in eight. But as artificial\nselection has lengthened the wings in some instances, why may it not\nhave shortened them in others? Wings with shortened bones would fold up\nmore neatly than the long wings of the Carrier pigeon for instance, and\nso might unconsciously be favoured by fanciers. The selection of elegant\nbirds with longer necks or bodies would cause a relative reduction in\nthe wings--as with the Pouter, where the wings have been greatly\nlengthened but not so much as the body.[28] Slender bodies, too, and the\nlessened divergence of the furculum,[29] would slightly diminish the\nspread of the wings, and so would affect the measurements taken. As the\nwing-bones, moreover, are to some extent correlated with the beak and\nthe feet, the artificial selection of shortened beaks might tend to\nshorten the wing as well as the feet. Under these circumstances how can\nwe be sure of the actual efficacy of use-inheritance? Surely selection\nis as fully competent to effect slight changes in the direction of\nuse-inheritance as it undoubtedly is to effect great changes in direct\nopposition to that alleged factor of evolution.\n\n\nSHORTENED BREAST-BONE IN PIGEONS.\n\nThe shortening of the sternum in pigeons is attributed to disuse of the\nflight muscles attached to it. The bone is only shortened by a third of\nan inch, but this represents a very remarkable reduction in proportional\nlength, which Darwin estimates at from one-seventh to one-eighth, or\nover 13 per cent. This marked reduction, too, quite unlike the slight\nreduction of the wing-bones to which the other ends of the muscles are\nattached, was universal in the eleven specimens measured by Darwin; and\nthe bone, though acknowledged to have been modified by artificial\nselection in some breeds, is not so open to observation as wings or\nlegs. Even, however, if this relative shortening of the sternum remained\notherwise inexplicable, it might still be as irrelevant to use and\ndisuse as is the fact that \"many breeds\" of fancy pigeons have lost a\nrib, having only seven where the ancestral rock-pigeon has eight.[30]\nBut the excessive reduction in the sternum is far from being\ninexplicable. In the first place Darwin has somewhat over-estimated it.\nInstead of comparing the deficiency of length with the increased length\nwhich _should_ have been acquired (since the pigeons have increased in\naverage size) he compares it with the length of the breast-bone in the\nrock-pigeon.[31] By this method if a pigeon had doubled in dimensions\nwhile its breast-bone remained unaltered, the reduction would be put\ndown as 100 per cent., whereas obviously the true reduction would be\none-half, or 50 per cent. of what the bone _should be_. Avoiding this\nerror and a minor fallacy besides, a sound estimate reduces the supposed\nreduction of 13 or 14 per cent. to one of 11.7 per cent., which is still\nof course a considerable diminution.\n\nPart of this reduction must be due to the direct effect of disuse during\nthe lifetime of the individual. Another and perhaps very considerable\npart of the relative change must be attributed to the lengthening of the\nneck or body by artificial selection, or to other modifications of\nshape and proportion effected directly or indirectly by the same\ncause.[32] The reduction is greatest in the Pouter (18-1/2 per cent.)\nand in the Pied Scanderoon (17-1/2 per cent.). In the former the body\nhas been greatly elongated by artificial selection and three or four\nadditional vertebrae have been acquired in the hinder part of the\nbody.[33] In the latter a long neck increases the length of the bird,\nand so causes, or helps to cause, the relative shortening of the\nbreast-bone. In the English Carrier--which experiences the effects of\ndisuse, as it is too valuable to be flown--the relative reduction of 11\nper cent. is apparently more than accounted for by the \"elongated\nneck.\" The Dragon also has a long neck. In the Pouter, although the\nbreast-bone has been shortened by 18-1/2 per cent. relatively to the\nlength of the body, it has _lengthened_ by 20 per cent. relatively to\nthe _bulk_ of the body.[34] Darwin forgot to ask whether allowance must\nnot be made for a frequent, or perhaps general, elongation of the neck\nand the hinder part of the body, and the relative shortening or the\nthrowing forward of the central portion containing the ribs (frequently\none less in number) and the sternum. The whole body of the pigeon is so\nmuch under the control of artificial selection, that every precaution\nmust be taken to guard against such possible sources of error.[35]\n\nUnder domestication there would be a suspension of the previous\nelimination of reduced breast-bones by natural selection (Weismann's\npanmixia), and a diminution of the parts concerned in flying might even\nbe favoured, as lessened powers of _continuous_ flight would prevent\npigeons from straying too far, and would fit them for domestication or\nconfinement. Such causes might reduce some of the less observed parts\naffected by flying, while still leaving the wing of full size for\noccasional flight, or to suit the requirements of the pigeon-fanciers. A\nchange might thus be commenced like that seen in the rudimentary keel of\nthe sternum in the owl-parrot of New Zealand, which has lost the power\nof flight although still retaining fairly-developed wings.\n\n\nSHORTENED FEET IN PIGEONS.\n\nDarwin thinks it highly probable that the short feet of most breeds of\npigeons are due to lessened use, though he owns that the effects of\ncorrelation with the shortened beak are more plainly shown than the\neffects of disuse.[36] But why need the inherited effects of disuse be\ncalled in to explain an average reduction of some 5 per cent., when\nDarwin's measurements show that in the breeds where long beaks are\nfavoured the principle of correlation between these parts has lengthened\nthe foot by 13 per cent. in spite of disuse?\n\n\nSHORTENED LEGS OF RABBITS.\n\nIn the case of the domestic rabbit Darwin notices that the bones of the\nlegs have (relatively) become shorter by an inch and a half. But as the\nleg-bones have _not_ diminished in relative weight,[37] they must\nclearly have grown _thicker_ or denser. If disuse has shortened them, as\nDarwin supposes, why has it also thickened them? The ears and the tail\nhave been lengthened in spite of disuse. Why then may not the ungainly\nhind-legs have been shortened by human preference independently of the\ninherited effects of disuse? By relying on apparently favourable\ninstances and neglecting the others it would be easy to arrive at all\nmanner of unsound conclusions. We might thus become convinced that\nvessels tend to sail northwards, or that a pendulum oscillates more\noften in one direction than in the other. It must not be forgotten that\nit would be easy to cite an enormous number of cases which are in direct\nconflict with the supposed law of use-inheritance.\n\n\nBLIND CAVE-ANIMALS.\n\nWeak or defective eyesight is by no means rare as a spontaneous\nvariation in animals, \"the great French veterinary Huzard going so far\nas to say that a blind race [of horses] could soon be formed.\" Natural\nselection evolves blind races whenever eyes are useless or\ndisadvantageous, as with parasites. This may apparently be done\nindependently of the effects of disuse, for certain neuter ants have\neyes which are reduced to a more or less rudimentary condition, and\nneuter termites are blind as well as wingless. In one species of ant\n(_Eciton vastator_) the sockets have disappeared as well as the eyes. In\ndeep caves not only would natural selection cease to maintain good\neyesight but it would persistently favour blindness--or the entire\nremoval of the eye when greatly exposed, as in the cave-crab--and as Dr.\nRay Lankester has indicated,[38] there would have been a previous\nselection of animals which through spontaneous weakness, sensitiveness,\nor other affection of the eye found refuge and preservation in the cave,\nand a subsequent selection of the descendants whose fitness for relative\ndarkness led them deeper into the cave or prevented them from straying\nback to the light with its various dangers and severer competition.\nPanmixia, however, as Weismann has shown, would probably be the most\nimportant factor in causing blindness.\n\n\nINHERITED HABITS.\n\nDarwin says: \"A horse is trained to certain paces, and the colt inherits\nsimilar consensual movements.\"[39] But selection of the constitutional\ntendency to these paces, and imitation of the mother by the colt, may\nhave been the real causes. The evidence, to be satisfactory, should show\nthat such influences were excluded. Men acquire proficiency in swimming,\nwaltzing, walking, smoking, languages, handicrafts, religious beliefs,\n&c., but the children only appear to inherit the innate abilities or\nconstitutional proclivities of their parents. Even the songs of birds,\nincluding their call-notes, are no more inherited than is language by\nman (_Descent of Man_, p. 86). They are learned from the parent.\nNestlings which acquire the song of a distinct species, \"teach and\ntransmit their new song to their offspring.\" If use-inheritance has not\nfixed the song of birds, why should we suppose that in a single\ngeneration it has transmitted a newly-taught method of walking or\ntrotting?\n\nIt is alleged that dogs inherit the intelligence acquired by association\nwith man, and that retrievers inherit the effects of their\ntraining.[40] But selection and imitation are so potent that the\nadditional hypothesis of use-inheritance seems perfectly superfluous.\nWhere intelligence is not highly valued and carefully promoted by\nselection, the intelligence derivable from association with man does\n_not_ appear to be inherited. Lap-dogs, for instance, are often\nremarkably stupid.\n\nDarwin also instances the inheritance of dexterity in seal-catching as a\ncase of use-inheritance.[41] But this is amply explained by the ordinary\nlaw of heredity. All that is needed is that the son shall inherit the\nsuitable faculties which the father inherited before him.\n\n\nTAMENESS OF RABBITS.\n\nDarwin holds that in some cases selection alone has modified the\ninstincts and dispositions of domesticated animals, but that in most\ncases selection and the inheritance of acquired habits have concurred in\neffecting the change. \"On the other hand,\" he says, \"habit alone in some\ncases has sufficed; hardly any animal is more difficult to tame than the\nyoung of the wild rabbit; scarcely any animal is tamer than the young of\nthe tame rabbit; but I can hardly suppose that domestic rabbits have\noften been selected for tameness alone; so that we must attribute at\nleast the greater part of the inherited change from extreme wildness to\nextreme tameness to habit and long-continued close confinement.\"[42]\n\nBut there are strong, and to me irresistible, arguments to the contrary.\nI think that the following considerations will show that the greater\npart, if not the whole, of the change must be attributed to selection\nrather than to the direct inheritance of acquired habit.\n\n(1) For a period which may cover thousands of generations, there has\nbeen an entire cessation of the natural selection which maintains the\nwildness (or excessive fear, caution, activity, &c.) so indispensably\nessential for preserving defenceless wild rabbits of all ages from the\nmany enemies that prey upon them.\n\n(2) During this same extensive period of time man has usually killed off\nthe wildest and bred from the tamest and most manageable. To some extent\nhe has done this consciously. \"It is very conducive to successful\nbreeding to keep only such as are quiet and tractable,\" says an\nauthority on rabbits,[43] and he enjoins the selection of the\nhandsomest and _best-tempered_ does to serve as breeders. To a still\ngreater extent man has favoured tameness unconsciously and indirectly.\nHe has systematically selected the largest and most prolific animals,\nand has thus doubled the size and the fertility of the domestic rabbit.\nIn consciously selecting the largest and most flourishing individuals\nand the best and most prolific mothers, he _must_ have unconsciously\nselected those rabbits whose relative _tameness_ or placidity of\ndisposition rendered it possible for them to flourish and to produce and\nrear large and thriving families, instead of fretting and pining as the\nwilder captives would do. When we consider how exceedingly delicate and\neasily disturbed yet all-important a function is that of maternity in\nthe continually breeding rabbit, we see that the tamest and the least\nterrified would be the most successful mothers, and so would continually\nbe selected, although man cared nothing for the tameness in itself. The\ntamest mothers would also be less liable to neglect or devour their\noffspring, as rabbits commonly do when their young are handled too soon,\nor even when merely frightened by mice, &c., or disturbed by changed\nsurroundings.\n\n(3) We must remember the extraordinary fecundity of the rabbit and the\nexcessive amount of elimination that consequently takes place either\nnaturally or artificially. Where nature preserved only the wildest, man\nhas preserved the tamest. If there is any truth in the Darwinian theory,\nthis thorough and long-continued reversal of the selective process\n_must_ have had a powerful effect. Why should it not be amply sufficient\nto account for the tameness and mental degeneracy of the rabbit without\nthe aid of a factor which can readily be shown to be far weaker in its\nnormal action than either natural or artificial selection? Why may not\nthe tameness of the rabbit be transferred to the group of cases in\nwhich Darwin holds that \"habit has done nothing,\" and selection has done\nall?\n\n(4) If use-inheritance has tamed the rabbit, why are the bucks still so\nmischievous and unruly? Why is the Angora breed the only one in which\nthe males show no desire to destroy the young? Why, too, should\nuse-inheritance be so much more powerful in the rabbit than with other\nanimals which are far more easily tamed in the first instance? Wild\nyoung rabbits when domesticated \"remain unconquerably wild,\" and,\nalthough they may be kept alive, they pine and \"rarely come to any\ngood.\" Yet the animal which _acquires_ least tameness--or apparently,\nindeed, none at all--inherits most! It appears, in fact, to inherit that\nwhich it cannot acquire--a circumstance which indicates the selection of\nspontaneous variations rather than the inheritance of changed habits.\nSuch variations occasionally occur in animals in a marked degree. Of a\nlitter of wolf-cubs, all brought up in the same way, \"one became tame\nand gentle like a dog, while the others preserved their natural\nsavagery.\" Is it not probable that permanent domestication was rendered\npossible by the inevitable selection of spontaneous variations in this\ndirection? The _excessive_ tameness, too, of the young rabbit, while\neasily explicable as a result of unconscious selection, is not easily\nexplained as a result of acquired habit. No particular care is taken to\ntame or teach or domesticate rabbits. They are bred for food, or for\nprofit or appearance, and they are left to themselves most of their\ntime. As Sir J. Sebright notices with some surprise, the domestic rabbit\n\"is not often visited, and seldom handled, and yet it is always tame.\"\n\n\nMODIFICATIONS OBVIOUSLY ATTRIBUTABLE TO SELECTION.\n\nInnumerable modifications in accordance with altered use or disuse, such\nas the enlarged udders of cows and goats, and the diminished lungs and\nlivers in highly bred animals that take little exercise, can be readily\nand fully explained as depending on selection. As the fittest for the\nnatural or artificial requirements will be favoured, natural or\nartificial selection may easily enlarge organs that are increasingly\nused and economize in those that are less needed. I therefore see no\nnecessity whatever for calling in the aid of use-inheritance as Darwin\ndoes, to account for enlarged udders, or diminished lungs, or the thick\narms and thin legs of canoe Indians, or the enlarged chests of\nmountaineers, or the diminished eyes of moles, or the lost feet of\ncertain beetles, or the reduced wings of logger-headed ducks, or the\nprehensile tails of monkeys, or the displaced eyes of soles, or the\naltered number of teeth in plaice, or the increased fertility of\ndomesticated animals, or the shortened legs and snouts of pigs, or the\nshortened intestines of tame rabbits, or the lengthened intestines of\ndomestic cats, &c.[44] Changed habits and the requisite change of\nstructure will usually be favoured by natural selection; for habit, as\nDarwin says, \"almost implies that some benefit great or small is thus\nderived.\"\n\n\nSIMILAR EFFECTS OF NATURAL SELECTION AND USE-INHERITANCE.\n\nHere we perceive a difficulty which will equally trouble those who\naffirm use-inheritance and those who deny. Broadly speaking, the\nadaptive effects ascribed to use-inheritance coincide with the effects\nof natural selection. The individual adaptability (as shown in the\nthickening of skin, fur, muscle, &c., under the stimulus of friction,\ncold, use, &c.) is identical in kind and direction with the racial\nadaptability under natural selection. Consequently the alleged\ninheritance of the advantageous effects of use and disuse cannot readily\nbe distinguished from the similarly beneficial effects of natural\nselection. The indisputable fact that natural selection imitates or\nsimulates the beneficial effects ascribed to use-inheritance may be the\nchief source and explanation of a belief which may prove to be\nthoroughly fallacious. A similar simulation of course occurs under\ndomestication, where natural selection is partly replaced by artificial\nselection of the best adapted and therefore most flourishing animals,\nwhile in disused parts panmixia or the comparative cessation of\nselection will aid or replace \"economy of growth\" in causing\ndiminution.[45]\n\n\nINFERIORITY OF SENSES IN EUROPEANS.\n\n\"The inferiority of Europeans, in comparison with savages, in eyesight\nand in the other senses,\" is attributed to \"the accumulated and\ntransmitted effect of lessened use during many generations.\"[46] But why\nmay we not attribute it to the slackened and diverted action of the\nnatural selection which keeps the senses so keen in some savage races?\n\n\nSHORT-SIGHT IN WATCHMAKERS AND ENGRAVERS.\n\nDarwin notices that watchmakers and engravers are liable to be\nshort-sighted, and that short-sight and long-sight certainly tend to be\ninherited.[47] But we must be careful not to beg the question at issue\nby assuming that the frequent heredity of short sight necessarily covers\nthe heredity of artificially-produced short-sight. Elsewhere, however,\nDarwin states more decisively that \"there is ground for believing that\nit may often originate in causes acting on the individual affected, and\nmay thence-forward become transmissible.\"[48] This impression may arise\n(1) from the facts of ordinary heredity--the ancestral liability being\nexcited in father and son by similar artificial habits, such as reading,\nand viewing objects closely as among watchmakers and engravers--or by\nconstitutional deterioration from indoor life, &c., acting upon a\nconstitutional liability of the eye to the \"something like inflammation\nof the coats, under which they yield\" and so cause shortness of sight\nby altering the spherical shape of the eye-ball. (2) Panmixia, or the\nsuspension of natural selection, together with altered habits, will\naccount for an increase of short-sight among the population generally.\n(3) Long-sighted people could not work at watchmaking and engraving so\ncomfortably and advantageously as at other occupations, and hence would\nbe less likely to take to such callings.\n\n\nLARGER HANDS OF LABOURERS' INFANTS.[49]\n\nThese are best explained as the result of natural selection and of the\ndiminution of the hand by sexual selection in the gentry. If the larger\nhands of labourers' infants are really due to the inherited effects of\nancestral use, why does the development occur so early in life, instead\nof only at a corresponding period, as is the rule? During the first few\nyears of its life, at least, the labourer's infant does no more work\nthan the gentleman's child. Why are not the effects of this disuse\ninherited by the labourer's infant? If the enlargement of the infant's\nhand illustrates the transference of a character gained later in life,\nit is evident that the transference must take place in spite of the\ninherited effects of disuse.\n\n\nTHICKENED SOLE IN INFANTS.\n\nDarwin also attributes the thickened sole in infants, \"long before\nbirth,\" to \"the inherited effects of pressure during a long series of\ngenerations.\"[50] But disuse should make the infant's sole _thin_, and\nit is this thinness that should be inherited. If we suppose the\ninheritance of the thickened soles of later life to be transferred to an\nearlier period, we have the anomaly of the inherited effects of disuse\nat that earlier period being overpowered by the untimely inheritance of\nthe effects of use at another. On the other hand, it is clear that\nnatural selection would favour thickened soles for walking on, and might\nalso promote an early development which would ensure their being ready\nin good time for actual use; for variations in the direction of delay\nwould be cut off, while variations in the other direction would be\npreserved. Anyhow, the mere transference of a character to an earlier\nperiod is no proof of use-inheritance. The real question is whether the\nthickened sole was gained by natural selection or by the inherited\neffects of pressure, and the mere transference or hastened appearance of\nthe thickening does not in any degree solve this question. It merely\nexcludes the effect of disuse during lifetime, and thus presents a\nfallacious appearance of being decisive. The thickened sole of the\nunborn infant, however, like the lanugo or hairy covering, is probably a\nresult of the direct inheritance of ancestral stages of evolution, of\nwhich the embryo presents a condensed epitome. While the relative\nthinness of the infant's sole might be pointed to as the effect of\n_disuse_ during a long series of generations, its thickness is rather an\nillustration of atavism still resisting the effects of long-continued\ndisuse. There is nothing to show that the inheritable portion of the\nfull original thickness was not gained by natural selection rather than\nby the directly inherited effect of use; and the latter, being\ncumulative and indiscriminative in its action, would apparently have\nmade the sole very much thicker and harder than it is. If natural\nselection were not supreme in such cases, how could we account for the\neffects of pressure resulting in hard hoofs in some cases and only soft\npads in others?\n\n\nA SOURCE OF MENTAL CONFUSION.\n\nOf course in a certain sense this thickening of the sole has resulted\nfrom use. In one sense or other, most--or perhaps all--of the results of\nnatural selection are inherited effects of use or disuse. Natural\nselection preserves that which is of use and which is used, while it\neliminates that which is useless and is not used. The most confident\nassertions of the effects of use and disuse in modifying the heritable\ntype, appear to rest on this indefeasible basis. Darwin's statements\nconcerning the effects of use and disuse in evolution can frequently be\nread in two senses. They often command assent as undeniable truisms as\nthey stand, but are of course written in another and more debatable\nsense. Thus in the case of the shortened wings and thickened legs of the\ndomestic duck, I believe equally with Darwin and Spencer that \"no one\nwill dispute that they have resulted from the lessened use of the wings\nand the increased use of the legs.\" \"Use\" is at bottom the determining\ncircumstance in evolution generally. The trunk of the elephant, the fin\nof the fish, the wing of the bird, the cunning hand of man and his\ncomplicated brain--and, in short, all organs and faculties\nwhatsoever--can only have been moulded and developed by use--by\nusefulness and by using--but not necessarily by use-inheritance, not\nnecessarily by directly inherited effects of use or disuse of parts in\nthe individual. So, too, reduced or rudimentary organs are due to\ndisuse, but it by no means follows that the diminution is caused by any\ndirect tendency to the inheritance of the effects of disuse in the\nindividual. The effects of natural selection are commonly expressible as\neffects of use and disuse, just as adaptation in nature is expressible\nin the language of teleology. But use-inheritance is no more proven by\none of these necessary coincidences than special design is by the\nother. The inevitable simulation of use-inheritance may be entirely\ndeceptive.\n\nDarwin thinks that \"there can be no doubt that use in our domestic\nanimals has strengthened and enlarged certain parts, and disuse\ndiminished them; and that such modifications are inherited.\" Undoubtedly\n\"such\" or _similar_ modifications have often been inherited, but how can\nDarwin possibly tell that they are not due to the simulation of\nuse-inheritance by natural or artificial selection acting upon general\nvariability? Of the inevitability of selection and of its generally\nadaptive tendencies \"there can be no doubt,\" and panmixia would tend to\nreduce disused parts; so that there _must always_ remain grave doubts of\nthe alleged inheritance of the similar effects of use and disuse, unless\nwe can accomplish the extremely difficult feat of excluding both natural\nand artificial selection as causes of enlargement, and panmixia and\nselection as causes of dwindling.\n\n\nWEAKNESS OF USE-INHERITANCE.\n\nUse-inheritance is normally so weak that it appears to be quite helpless\nwhen opposed to any other factor of evolution. Natural selection evolves\nand maintains the instincts of ants and termites in spite of\nuse-inheritance to a more wonderful degree than it evolves the instincts\nof almost any other animal with the fullest help of use-inheritance. It\ndevelops seldom-used horns or natural armour just as readily as\nconstantly-used hoofs or teeth. Sexual selection evolves elaborate\nstructures like the peacock's tail in spite of disuse and natural\nselection combined. Artificial selection appears to enlarge or diminish\nused parts or disused parts with equal facility. The assistance of\nuse-inheritance seems to be as unnecessary as its opposition is\nineffective.\n\nThe alleged inheritance of the effects of use and disuse in our domestic\nanimals must be very slow and slight.[51] Darwin tells us that \"there\nis no good evidence that this ever follows in the course of a single\ngeneration.\" \"Several generations must be subjected to changed habits\nfor any appreciable result.\"[52] What does this mean? One of two things.\nEither the tendency is very weak, or it is non-existent. If it is so\nweak that we cannot detect its alleged effects till several generations\nhave elapsed, during which time the more powerful agency of selection\nhas been at work, how are we to distinguish the effects of the minor\nfactor from that of the major? Are we to conclude that use-inheritance\n_plus_ selection will modify races, just as Voltaire firmly held that\nincantations, together with sufficient arsenic, would destroy flocks of\nsheep? Is it not a significant fact that the alleged instances of\nuse-inheritance so often prove to be self-conflicting in their details?\n\nFor satisfactory proof of the prevalence of a law of use-inheritance we\nrequire normal instances where selection is clearly inadequate to\nproduce the change, or where it is scarcely allowed time or opportunity\nto act, as in the immediate offspring of the modified individual. Of the\nfirst kind of cases there seems to be a plentiful lack. Of the latter\nkind, according to Darwin, there appears to be none--a circumstance\nwhich contrasts strangely and suspiciously with the many decisive cases\nin which variation from unknown causes has been inherited most\nstrikingly in the immediate offspring. It must be expected, indeed, that\namong these innumerable cases some will accidentally mimic the alleged\neffects of use-inheritance.\n\nIf Darwin had felt certain that the effects of habit or use tended in\nany marked degree to be conveyed directly and cumulatively to succeeding\ngenerations, he could hardly have given us such cautious, half-hearted\nencouragement of good habits as the following:--\"It is not improbable\nthat after long practice virtuous tendencies may be inherited.\" \"Habits,\nmoreover followed during many generations probably tend to be\ninherited.\"[53] This is probable, independently of use-inheritance. The\n\"many generations\" specified or implied, will allow time for the play of\nselective as well as of cumulatively-educative influences. There must\napparently be a constitutional or inheritable predisposition or fitness\nfor the habits spoken of, which otherwise would scarcely be continued\nfor many generations, except by the favourably-varying branches of a\nfamily: which again is selection rather than use-inheritance.\n\nWhere is the necessity for even the remains of the Lamarckian doctrine\nof inherited habit? Seeing how powerful the general principle of\nselection has shown itself in cases where use-inheritance could have\ngiven no aid or must even have offered its most strenuous opposition,\nwhy should it not equally be able to develop used organs or repress\ndisused organs or faculties without the assistance of a relatively weak\nally? Selection evolved the remarkable protective coverings of the\narmadillo, turtle, crocodile, porcupine, hedgehog, &c.; it formed alike\nthe rose and its thorn, the nut and its shell; it developed the\npeacock's tail and the deer's antlers, the protective mimicry of various\ninsects and butterflies, and the wonderful instincts of the white ants;\nit gave the serpent its deadly poison and the violet its grateful odour;\nit painted the gorgeous plumage of the Impeyan pheasant and the\nbeautiful colours and decorations of countless birds and insects and\nflowers. These, and a thousand other achievements, it has evidently\naccomplished without the help of use-inheritance. Why should it be\nthought incapable of reducing a pigeon's wing or enlarging a duck's\nleg? Why should it be credited with the help of an officious ally in\neffecting comparatively slight changes, when great and striking\nmodifications are effected without any such aid?\n\n\nFOOTNOTES:\n\n[15] Weismann's _Essays on Heredity_, &c. Clarendon Press, 1889.\n\n[16] _Life and Letters_, i. p. 16. Darwin's reverence for his father\n\"was boundless and most touching. He would have wished to judge\neverything else in the world dispassionately, but anything his father\nhad said was received with almost implicit faith; ... he hoped none of\nhis sons would ever believe anything because he said it, unless they\nwere themselves convinced of its truth--a feeling in striking contrast\nwith his own manner of faith\" (_Life and Letters_, i. pp. 10, 11).\n\n[17] _Ibid._, i. p. 38.\n\n[18] _Life and Letters_, ii. p. 14.\n\n[19] _Origin of Species_, pp. 117, 118.\n\n[20] _Ibid._, p. 180.\n\n[21] _Contemporary Review_, December, 1875, pp. 89, 93.\n\n[22] _Variation of Animals and Plants under Domestication_, i. 292.\n\n[23] _Variation of Animals and Plants under Domestication_, i. 299-301.\n\n[24] To keep pace with this lateral increase in weight, the leg-bones\nshould have lengthened considerably so that their total deficiency in\nproportional length is 17 per cent.,--a changed proportion which being\n_linear_ is more excessive than the increase of weight by 28 per cent.\nSo marked is the effect of the combined thickening and shortening that\nin the Aylesbury breed--which is the most typically representative\none--the leg-bones have become 70 per cent. heavier than they should be\nif their thickness had continued to be proportional to their length.\n\n[25] This excessive thickening under disuse appears to be due partly to\na positive lateral enlargement or increase of proportional weight of\nabout 7-1/2 per cent., and partly to a shortening of about 15 per cent.\nCarefully calculated, the reduction of the weight of the wing-bones in\nthis breed is only 8.3 per cent. relatively to the whole skeleton, or\nonly 5 per cent. relatively to the skeleton _minus_ legs and wings. The\nlatter method is the more correct, since the excessive weight of the\nleg-bones increases the weight of the skeleton more than the diminished\nweight of the wing-bones reduces it.\n\n[26] _Variation of Animals and Plants under Domestication_, i. 284.\n\n[27] _Variation of Animals and Plants under Domestication_, i. 184, 185.\n\n[28] _Ibid._, i. 144, 145.\n\n[29] _Ibid._, i. 185.\n\n[30] _Variation of Animals and Plants under Domestication_, i. 175.\n\n[31] _Variation of Animals and Plants under Domestication_, i. 184. I\nsuspect that Darwin was in poor health when he wrote this page. He nods\nat least four times in it. Twice he speaks of \"twelve\" breeds where he\nobviously should have said eleven.\n\n[32] If a prominent breast is admired and selected by fanciers, the\nsternum might shorten in assuming a more forward and vertical position.\nIf the shortening of the sternum is entirely due to disuse, it seems\nstrange that Darwin has not noticed any similar shortening in the\nsternum of the duck. But selection has not tended to make the duck\nelegant, or \"pigeon-breasted\"; it has enlarged the abdominal sack\ninstead, besides allowing the addition of an extra rib in various cases.\n\n[33] _Variation of Animals and Plants under Domestication_, 144, 175.\n\n[34] _Variation of Animals and Plants under Domestication_, i. 179.\n\n[35] In the six largest breeds the shortening of the sternum is nearly\ntwice as great as in the three smaller breeds which remain nearest the\nrock-pigeon in size. We can hardly suppose that use-inheritance\nespecially affects the eight breeds that have varied most in size. If we\nexclude these, there is only a total shortening of 7 per cent. to be\naccounted for.\n\n[36] _Variation of Animals and Plants under Domestication_, i. 183, 186.\n\n[37] _Variation of Animals and Plants under Domestication_, i. 130, 135;\nii. 288.\n\n[38] _Encyclopaedia Britannica_, article \"Zoology.\"\n\n[39] _Variation of Animals and Plants under Domestication_, ii. 367.\n\n[40] _Variation of Animals and Plants under Domestication_, ii. 367. Why\nthen does the cheetah inherit ancestral habits so inadequately that it\nis useless for the chase unless it has first learned to hunt for itself\nbefore being captured? (ii. 133).\n\n[41] _Descent of Man_, p. 33.\n\n[42] _Origin of Species_, pp. 210, 211.\n\n[43] E. S. Delamer on _Pigeons and Rabbits_, pp. 132, 103. For other\npoints referred to, see pages 133, 102, 100, 95, 131.\n\n[44] _Origin of Species_, pp. 188, 110; _Descent of Man_, pp. 32-35;\n_Variation of Animals and Plants under Domestication_, ii. 289, 293. Use\nor disuse during lifetime of course co-operates, and in some cases, as\nin that of the canoe Indians, may be the principal or even perhaps the\n_sole_ cause of the change.\n\n[45] For the importance of panmixia as invalidating Darwin's strongest\nevidence for use-inheritance--namely, that drawn from the effects of\ndisuse in highly-fed domestic animals where there is supposed to be no\neconomy of growth--see Professor Romanes on Panmixia, _Nature_, April 3,\n1890.\n\n[46] _Descent of Man_, p. 33.\n\n[47] _Descent of Man_, p. 33.\n\n[48] _Variation of Animals and Plants under Domestication_, i., 453.\n\n[49] _Descent of Man_, p. 33.\n\n[50] _Descent of Man_, p. 33.\n\n[51] Wallace shows that the changes in our domestic animals, if spread\nover the thousands of years since the animals were first tamed, must be\nextremely insignificant in each generation, and he concludes that such\ninfinitesimal effects of use and disuse would be swallowed up by the far\ngreater effects of variation and selection (_Darwinism_, p. 436).\nProfessor Romanes has replied to him in the _Contemporary Review_\n(August 1889), showing that this is no disproof of the existence of the\nminor factor, inasmuch as slight changes in each generation need not\nnecessarily be matters of life and death to the individual, although\ntheir cumulative development by use-inheritance might eventually become\nof much service. But selection would favour spontaneous variations of a\nsimilarly serviceable character. The slightest tendency to eliminate the\nextreme variations in either direction would proportionally modify the\naverage in a breed. Use-inheritance appears to be so relatively weak a\nfactor that probably neither proof nor disproof of its existence can\never be given, owing to the practical impossibility of disentangling its\neffects (if any) from the effects of admittedly far more powerful\nfactors which often act in unsuspected ways. Thus wild ducklings, which\ncan easily be reared by themselves, invariably \"die off\" if reared with\ntame ones (_Variation_, &c., i. 292, ii. 219). They cannot get their\nfair share in the competition for food, and are completely eliminated.\nProfessor Romanes fully acknowledges that there is the \"gravest possible\ndoubt\" as to the transmission of the effects of disuse (Letter on\nPanmixia, _Nature_, March 13, 1890).\n\n[52] _Variation of Animals and Plants under Domestication_, ii. 287-289.\n\n[53] _Descent of Man_, pp. 612, 131.\n\n\n\n\nINHERITED INJURIES.\n\n\nINHERITED MUTILATIONS.\n\nThe almost universal _non-inheritance_ of mutilations seems to me a far\nmore valid argument _against_ a general law of modification-inheritance\nthan the few doubtful or abnormal cases of such inheritance can furnish\nin its favour. No inherited effect has been produced by the docking of\nhorses' tails for many generations, or by a well-known mutilation which\nhas been practised by the Hebrew race from time immemorial. As lost or\nmutilated parts are reproduced in offspring independently of the\nexistence of those parts in the parent, there is the less reason to\nsuppose that the particular condition of parental parts transmits\nitself, or tends to transmit itself, to the offspring. So unsatisfactory\nis the argument derivable from inherited mutilations that Mr. Spencer\ndoes not mention them at all, and Darwin has to attribute them to a\nspecial cause which is independent of any general theory of\nuse-inheritance.[54]\n\nDarwin's most striking case--and to my mind the only case of any\nimportance--is that of Brown-Sequard's epileptic guinea-pigs, which\ninherited the mutilated condition of parents who had gnawed off their\nown gangrenous toes when anaesthetic through the sciatic nerve having\nbeen divided.[55] Darwin also mentions a cow that lost a horn by\naccident, followed by suppuration, and subsequently produced three\ncalves which had on the same side of the head, instead of a horn, a bony\nlump attached merely to the skin. Such cases may seem to prove that\nmutilation _associated with morbid action_ is occasionally inherited or\nrepeated with a promptitude and thoroughness that contrast most\nstrikingly with the imperceptible nature of the immediate inheritance of\nthe effects of use and disuse; but they by no means prove that\nmutilation in general is inheritable, and they are absolutely no proof\nwhatever of a _normal_ and non-pathological tendency to the inheritance\nof acquired characters. Those who accept Darwin's special explanation\nof the supposed inheritance of mutilations, ought to notice that his\nexplanation applies equally well under a theory which is strongly\nadverse to use-inheritance--namely, Galton's idea of the sterilization\nand complete \"using up\" of otherwise reproductive matter in the growth\nand maintenance of the personal structure.\n\nDarwin's explanation of inherited mutilations--which, as he notes, occur\n\"especially or perhaps exclusively\" when the injury has been followed by\ndisease[56]--is that all the representative gemmules which would develop\nor repair or reproduce the injured part are attracted to the diseased\nsurface during the reparative process and are there destroyed by the\nmorbid action.[57] Hence they cannot reproduce the part in offspring.\nThis explanation by no means implies that mutilation would _usually_\naffect the offspring. On the contrary, in all ordinary cases of\nmutilation the purely atavistic elements or gemmules would be set free\nfrom any modifying influence of the non-existent or mutilated part. The\ngemmules--as in Galton's theory of heredity and with neuter\ninsects--might be perfectly independent of pangenesis and the normal\ninheritance of acquired characters. Such self-multiplying gemmules\nwithout pangenesis would enable us to understand both the excessive\nweakness or non-existence of normal use-inheritance, and the excessive\nstrength and abruptness of the effect of their partial destruction under\nspecial pathological conditions.\n\nThe series of epileptic phenomena that can be excited by tickling a\ncertain part of the cheek and neck of the adult guinea-pig during the\ngrowth and rejoining of the ends of the severed nerve, are said to be\nrepeated with striking accuracy of detail in the young who inherit\nmutilated toes; but as epilepsy is often due to some _one_ exciting\ncause or morbid condition, the single transmission of a highly morbid\ncondition of the system might easily reproduce the whole chain of\nconsequences and might also have caused the loss of toes.\n\nThe particulars of the guinea-pig cases are very inadequately\nrecorded,[58] but the results are so anomalous[59] that Brown-Sequard's\nown conclusion is that the epilepsy and the inherited injuries are\n_not_ directly transmitted, but that \"what is transmitted is the morbid\nstate of the nervous system.\" He thinks that the missing toes may\n\"possibly\" be exceptions to this conclusion, \"but the other facts only\nimply the transmission of a morbid state of the sympathetic or sciatic\nnerve or of a part of the medulla oblongata.\" Until we can tell what is\ntransmitted, we are not in a position to determine whether there is any\ntrue inheritance or only an exaggerated simulation of it under peculiar\ncircumstances. When the actual observers believe that the mutilations\nand epilepsy are not the cause of their own repetition, and when these\nobservers guard themselves by such phrases as, \"if any conclusion can at\npresent be drawn from those facts,\" we who have only incomplete reports\nto guide us may well be excused if we preserve an even more pronounced\nattitude of caution and reserve.[60] The morbid state of the system may\nbe wholly due to general injury of the germs rather than to specific\ninheritance.\n\nWeismann suggests that the morbid condition of the nervous system may be\ndue to some infection such as might arise from microbes, which find a\nhome in the mutilated and disordered nervous system in the parent, and\nsubsequently transmit themselves to the offspring through the\nreproductive elements, as the infections of various diseases appear to\ndo--the muscardine silkworm disease in particular being known to be\nconveyed to offspring in this manner.\n\nBut whether we can discover the true explanation or not, inherited\nmutilations can hardly be accounted for as the result of a general\ntendency to inherit acquired modifications. How could a factor which\nseems to be totally inoperative in cases of ordinary mutilation, and\nonly infinitesimally operative in transmitting the normal effects of use\nand disuse, suddenly become so powerful as to completely overthrow\natavism, and its own tendency to transmit the non-mutilated type of one\nof the parents and of the non-mutilated type presented by the injured\nparent in earlier life? Does not so striking and abrupt an\nintensification of its usually insignificant power demand an explanation\nwidely different from that which might account for the extremely slow\nand slight inheritance of the normal effects of use and disuse? Surely\nit would be better to suspend one's judgment as to the true explanation\nof highly exceptional and purely pathological cases rather than resort\nto an hypothesis that creates more difficulties than it solves.\n\n\nTHE MOTMOT'S TAIL.\n\nThe narrowing of the long central tail feathers of the motmot is\nattributed to the inherited effects of habitual mutilation (_Descent of\nMan_, pp. 384, 603). But in the specimens at South Kensington[61] the\nnarrowness extends upwards much beyond the habitually denuded part, and\nthe broadened end is the broadest part of the whole feather. If the\ninherited effect of an inch or two of denudation extends from three to\nsix inches upwards, why has it not also extended two inches downwards so\nas to narrow the broadened end? The narrowness seems to be a mainly\nrelative or negative effect produced by the broadening out of a long\ntapering feather at its end under the influence of sexual selection.\nSeveral other birds have similarly narrowed or spoon-shaped feathers and\ndo not bite them. Is it not more feasible to suppose that this\nattractive peculiarity first suggested its artificial intensification,\nthan to suppose that the bird began nibbling without any definite cause?\nSexual selection would then encourage the habit. Anyhow, it is as\nimpossible to show that the mutilation preceded the narrowing as it is\nto show that tonsure preceded baldness.\n\n\nOTHER INHERITED INJURIES MENTIONED BY DARWIN.\n\nDarwin quotes some cases from Dr. Prosper Lucas's \"long\" but weak and\nunsatisfactory \"list of inherited injuries.\"[62] But Lucas was somewhat\ncredulous. One of his cases is that many girls were born in London\nwithout mammae through the injurious effect of certain corsets on the\nmothers. He also gives a long account of a Jew who could read through\nthe thick covers of a book, and whose son inherited this \"hyperaesthesia\"\nof the sense of sight in a still more remarkable degree (i. 113-119).\nEvidently Lucas's cases cannot be accepted without some amount of\nreserve.\n\nThe cases of the three calves which inherited the one-horned condition\nof the cow, the two sons who inherited a father's crooked finger, and\nthe two sons who were microphthalmic on the same side as their father\nhad lost an eye, may be due to mere coincidence; or an inherited\nconstitutional tendency or liability might lead to somewhat similar\nresults in parent and offspring[63]--just as the tendency to certain\nfatal diseases or to suicide may produce similar results in father and\nson, although the artificially-produced hanging or apoplexy obviously\ncannot be directly transmitted. That more than one of the offspring was\naffected does not render the chances against coincidence \"almost\ninfinitely great,\" as Darwin mistakenly supposes. It \"frequently occurs\"\nthat a man's sons or daughters may _all_ exhibit either a latent or a\nnewly-developed congenital peculiarity previously unknown;[64] and the\ncoincidence may merely be that one of the parents accidentally suffered\na similar kind of injury--a kind of coincidence which must of course\noccasionally occur, and which may have been partly caused by a latent\ntendency. The chances against coincidence are indeed great, but the\ncases appear to be correspondingly rare.\n\nDarwin acknowledges that many supposed instances of inherited mutilation\nmay be due to coincidence; and there is apparently no more reason for\nattributing inherited scars, &c., to any special form of heredity than\nto the effect of the mother's imagination on the unborn babe--a popular\nbut fallacious belief in corroboration of which far more alleged\ninstances could be collected than of the inheritance of injuries.\n\nAs an instance of the coincidences that occur, I may mention that a\nfriend of mine has a daughter who was born with a small hole in one ear,\njust as if it were already pierced for the earring which she has since\nworn in it. I suppose, however, that no one will venture to claim this\nas an instance of the inheritance of a mutilation practised by female\nancestors, especially as such holes are not altogether unknown or\ninexplicable, though very rarely occurring low down in the lobe of the\near.[65]\n\nMany cases are known of the inheritance of mutilations or malformations\narising congenitally from some abrupt variation in the reproductive\nelements. In such cases as the one-eared rabbits, the two-legged pigs,\nthe three-legged dogs, the one-horned stags, hornless bulls, earless\nrabbits, lop-eared rabbits, tailless dogs, &c., if the father or the\nmother or the embryo had suffered from some accident or disease which\nmight plausibly have been assigned as the cause of the original\nmalformation, these transmitted defects would readily be cited as\ninstances of the inheritance of an accidentally-produced modification.\n\nThe inheritance of exostoses on horses' legs may be the inheritance of a\nconstitutional tendency rather than of the effect of the parents' hard\ntravelling. Horses congenitally liable to such formations would transmit\nthe liability,[66] and this might readily be mistaken for inheritance of\nthe results of the liability. An apparent increase in this liability\nmight arise from greater attention being now paid to it, or from\nincreased use of harder roads; or a real increase might be due to\npanmixia and some obscure forms of correlation.\n\n\nQUASI-INHERITANCE.\n\nOf course artificially-caused ill-health or weakness in parents will\ntend in a general way to injure the offspring. But deterioration thus\ncaused is only a form of quasi-inheritance, as I should prefer to call\nit. Semi-starvation in a new-born babe is _not_ truly inherited from its\nhalf-starved mother, but is the direct result of insufficient\nnourishment. The general welfare of germs--as of parasites--is\nnecessarily bound up with that of the organism which feeds and shelters\nthem, but this is not heredity, and is quite irrelevant to the question\nwhether particular modifications are transmitted or not.\n\nAnother form of quasi-inheritance is seen in the communication of\ncertain infections to offspring. Not being transmitted by the action of\nthe organism so much as in defiance of it, such diseases are not truly\nhereditary, though for convenience' sake they are usually so described.\n\nA perversion or prevention of true inheritance is also seen in the\naction of alcohol, or excessive overwork, or any other cause which by\noriginating morbid conditions in individuals may also injure the\nreproductive elements.\n\nThese forms of quasi-inheritance are, of course, highly important so far\nas the improvement of the race is concerned. So, too, is the fact that\nimproved or deteriorated habits and thoughts are transmitted by personal\nteaching and influence and are cumulative in their effect. But all this\nmust not be confounded with the inheritance of acquired characters.\nCases of quasi-inheritance may perhaps be most readily distinguished\nfrom cases of true inheritance by the time test. When a modification\nacquired in adult life is promptly communicated to the child in early\nlife or from birth, it may rightly be suspected that the inheritance,\nlike that of money or title, is not truly congenital, but is extraneous\nor even anti-congenital in its nature. Judged by such a standard, the\ninherited injuries in Brown-Sequard's guinea-pigs are only exceptional\ncases of quasi-inheritance, and are not necessarily indicative of any\ngeneral rule affecting true inheritance.\n\n\nFOOTNOTES:\n\n[54] A very able anatomist of my acquaintance denies the inheritance of\nmutilations and injuries, although he strongly believes in the\ninheritance of the effects of use and disuse.\n\n[55] _Variation of Animals and Plants under Domestication_, i. 467-469.\nLost toes were only seen by Dr. Dupuy in three young out of two hundred.\nObersteiner found that most of the offspring of his epileptic\nguinea-pigs were injuriously affected, being weakly, small, paralysed in\none or more limbs, and so forth. Only two were epileptic, and both were\nweakly and died early (Weismann's _Essays_, p. 311). A morbid condition\nof the spinal cord might affect the hind limbs especially (as in\nparaplegia) and might occasionally cause loss of toes in the embryo by\npreventing development or by ulceration. Brown-Sequard does not say that\nthe defective feet were on the same side as in the parents (_Lancet_,\nJan., 1875, pp. 7, 8).\n\n[56] _Variation of Animals and Plants under Domestication_, ii. 57.\n\n[57] _Ibid._, ii. 392. Perhaps it might be better to suppose that the\n_best_ gemmules were sacrificed in repairing the injured _nerve_, and\nhence only inferior substitutes were left to take their place, and could\nonly imperfectly reproduce the injured part of the nervous system in\noffspring.\n\n[58] Hence perhaps Mr. Spencer's error in representing the epileptic\nliability as permanent and as coming on _after_ healing (_Factors of\nOrganic Evolution_, p. 27).\n\n[59] It is not claimed that the imperfect foot was on the same side of\nthe body as in the parent, and where parents had lost _all_ the toes of\na foot, or the whole foot, the few offspring affected usually had lost\nonly two toes out of the three, or only a part of one or two or three\ntoes. Sometimes the offspring had toes missing on _both_ hind feet,\nalthough the parent was only affected in _one_. _One_ diseased ear and\neye in the parent was \"generally\" or \"always\" succeeded by _two_ equally\naffected ears and eyes in the offspring (cf. _Pop. Science Monthly_, New\nYork, xi. 334). The important law of inheritance at corresponding\nperiods was also set aside. Gangrene or inflammation commenced in both\nears and both eyes soon after birth (pointing possibly to infection of\nsome kind); the epileptic period commenced \"perhaps two months or more\nafter birth,\" while the loss of toes had occurred before birth. In no\ncase, as Weismann points out, is the original mutilation of the nervous\nsystem ever transmitted. Even where an extirpated ganglion was never\nregenerated in the parent, the offspring always regained the part in an\napparently perfect condition. On the whole the conflicting results ought\nto be as puzzling to those who may attribute them to a universal\ntendency to inherit the exact condition of parents as they are to those\nwho, like myself, are sceptical as to the existence of such a law or\ntendency.\n\n[60] The various results need to be fully and impartially recorded, and\nthey should also be well tested and confirmed in proportion as they\nappear improbable and contrary to general experience. Professor Romanes\nhas been carrying out the necessary experiments for some time past.\n\n[61] Natural History Museum, central hall, third recess on the left.\n\n[62] _Traite de l'Heredite_, ii. 489; _Variation of Animals and Plants\nunder Domestication_, i. 469. If injuries are inherited, why has the\nrepeated rupture of the hymen produced no inherited effect?\n\n[63] Compare the three cases of crooked fingers given in _Variation of\nAnimals and Plants under Domestication_, ii. 55, 240.\n\n[64] _Ibid._, i. 460. Thus, where two brothers married two sisters all\nthe seven children were perfect albinos, although none of the parents or\ntheir relatives were albinos. In another case the nine children of two\nsound parents were all born blind (ii. 322).\n\n[65] See pp. 179-182, _Evolution and Disease_, by J. Bland Sutton, to\nwhom and to our mutual friend Dr. D. Thurston I am indebted for\ninformation on various points.\n\n[66] _Variation of Animals and Plants under Domestication_, ii. 290; i.\n454.\n\n\n\n\nMISCELLANEOUS CONSIDERATIONS.\n\n\nTRUE RELATION OF PARENTS AND OFFSPRING.\n\nIt is difficult to entirely free ourselves from the flattering and\nalmost universal idea that parents are true originators or creators of\ncopies of themselves. But the main truth, if not the whole truth, is\nthat they are merely the transmitters of types of which they and their\noffspring are alike more or less similarly moulded resultants. A parent\nis a trustee. He transmits, not himself and his own modifications, but\nthe stock, the type, the representative elements, of which he is a\nproduct and a custodian in one. It seems probable that he has no more\ndefinite or \"particulate\" influence over the reproductive elements\nwithin him than a mother over the embryo or a vessel over its cargo.\nParent and offspring are like successive copies of books printed from\nthe same \"type.\" A battered letter in the \"type\" will display its\neffects in both earlier and later copies alike, but a purely extraneous\nor acquired flaw in the first copy is not necessarily repeated in\nsubsequent copies. Unlike printer's type, however, the material source\nof heredity is of a fluctuating nature, consisting of competing elements\nderived from two parents and from innumerable ancestors.\n\nGalton compares parent and child to successive pendants on the same\nchain. Weismann likens them to successive offshoots thrown up by a long\nunderground root or sucker. Such comparisons indicate the improbability\nof acquired modifications being transmitted to offspring.\n\nThat parts are developed in offspring independently of those parts in\nparents is clear. Mutilated parents transmit parts which they do not\npossess. The offspring of young parents cannot inherit the later stages\nof life from parents who have not passed through them. Cases of remote\nreversion or atavism show that ancestral peculiarities can transmit\nthemselves in a latent or undeveloped condition for hundreds or\nthousands of generations. Many obvious facts compelled Darwin to suppose\nthat vast numbers of the reproductive gemmules in an individual are not\nthrown off by his own cells, but are the self-multiplying progeny of\nancestral gemmules. Galton restricts the production of gemmules by the\npersonal structure to a few exceptional cases, and would evidently like\nto dispense with pangenesis altogether, if he could only be sure that\nacquired characters are never inherited. Weismann entirely rejects\npangenesis and the inheritance of acquired characters. This enables him\nto explain heredity by his theory of the \"Continuity of the\nGerm-plasm.\"[67] Parent and offspring are alike successive products or\noffshoots of this persistent germ-substance, which obviously would not\nbe correspondingly affected by modifications of parts in parents, and so\nwould render the transmission of acquired characters impossible.\n\n\nINVERSE INHERITANCE.\n\nMr. Galton contends that the reproductive elements become sterile when\nused in forming and maintaining the individual, and that only a small\nproportion of them are so used.[68] He holds that the next generation\nwill be formed entirely, or almost entirely, from the residue of\nundeveloped germs, which, not having been employed in the structure and\nwork of the individual, have been free to multiply and form the\nreproductive elements whence future individuals are derived. Hence the\nsingular inferiority not infrequently displayed by the children of men\nof extraordinary genius, especially where the ancestry has been only of\na mediocre ability. The valuable germs have been used up in the\nindividual, and rendered sterile in the structure of his person. Hence,\ntoo, the \"strong tendency to deterioration in the transmission of every\nexceptionally gifted race.\" Mr. Galton's hypothesis \"explains the fact\nof certain diseases skipping one or more generations,\" and it \"agrees\nsingularly well with many classes of fact;\" and it is strongly opposed\nto the theory of use-inheritance. The elements which are used die almost\nuniversally without germ progeny: the germs which are _not_ used are the\ngreat source of posterity. Hence, when the germs or gemmules which\nachieve development are either better or worse than the residue, the\nqualities transmitted to offspring will be of an inverse character. If\nbrain-work attracts, develops _and sterilizes_ the best gemmules, the\nultimate effect of education on the intellect of posterity may differ\nfrom its immediate effect.\n\n\nEARLY ORIGIN OF THE OVA.\n\nAs the ova are formed at as early a period as the rest of the maternal\nstructure, Galton notices that it seems improbable that they would be\ncorrespondingly affected by subsequent modifications of parental\nstructure. Of course it is not certain that this is a valid argument. We\nknow that the paternal half of the reproductive elements does not enter\nthe ovum till a comparatively late stage in its history, and it is quite\npossible that maternal elements or gemmules may also enter the ovum from\nwithout. If reproductive elements were confined to one special part or\norgan, we should be unable to explain the reproduction of lost limbs in\nsalamanders, and the persistent effect of intercrossing on subsequent\nissue by the same mother, and the propagation of plants from shoots, or\nof the begonia from minute fragments of leaves, or the development of\nsmall pieces of water-worms into complete animals.\n\n\nMARKED EFFECTS OF USE AND DISUSE ON THE INDIVIDUAL.\n\nThese are, to some extent, an argument against the cumulative\ninheritance of such effects. When a nerve atrophies from disuse, or a\nduct shrivels, or bone is absorbed, or a muscle becomes small or flabby,\nit proves, so far, that the average effect of use through enormous ages\nis _not_ transmitted. When the fibula of a dog's leg thickens by 400 per\ncent. to a size \"equal to or greater than\" that of the removed tibia\nwhich previously did the work,[69] it shows that in spite of disuse for\ncountless generations, the \"almost filiform\" bone has retained a\npotentiality of development which is fully equal to that possessed by\nthe larger one which has been constantly used. When, after being reared\non the ailanthus, the caterpillars of the _Bombyx hesperus_ die of\nhunger rather than return to their natural food, the inherited effect of\nancestral habit does not seem to be particularly strong. Neither is\nthere any strongly-inherited effect of long-continued ancestral wildness\nin many animals which are easily tamed.\n\n\nWOULD NATURAL SELECTION FAVOUR USE-INHERITANCE?\n\nIf use-inheritance is really one of the factors of evolution, it is\ncertainly a subordinate one, and an utterly helpless one, whenever it\ncomes into conflict with the great ruling principle of Selection. Would\nthis dominant cause of evolution have favoured a tendency to\nuse-inheritance if such had appeared, or would it have discouraged and\ndestroyed it? We have already seen that use-inheritance is unnecessary,\nsince natural selection will be far more effective in bringing about\nadvantageous modifications; and if it can be shown that use-inheritance\nwould often be an evil, it then becomes probable that on the whole\nnatural selection would more strongly discourage and eliminate it as a\nhostile factor than it might occasionally favour such a tendency as a\ntotally unnecessary aid.\n\n\nUSE-INHERITANCE AN EVIL.\n\nUse-inheritance would crudely and indiscriminately proportion parts to\nactual work done--or rather to the varying _nourishment and growth_\nresulting from a multiplicity of causes--and this in its various details\nwould often conflict most seriously with the real necessities of the\ncase, such as occasional passive strength, or appropriate shape,\nlightness and general adaptation. If its accumulated effects were not\ncorrected by natural or sexual selection, horns and antlers would\ndisappear in favour of enlarged hoofs. The elephant's tusks would become\nsmaller than its teeth. Men would have callosities for sitting on, like\ncertain monkeys, and huge corns or hoofs for walking on. Bones would\noften be modified disastrously. Thus the condyle of the human jaw would\nbecome larger than the body of the jaw, because as the fulcrum of the\nlever it receives more pressure. Some organs (like the heart, which is\nalways at work) would become inconveniently or unnecessarily large.\nOther absolutely indispensable organs, which are comparatively passive\nor are very seldom used, would dwindle until their weakness caused the\nruin of the individual or the extinction of the species. In eliminating\nvarious evil results of use-inheritance, natural selection would be\neliminating use-inheritance itself. The displacement of Lamarck's theory\nby Darwin's shows that the effects of use-inheritance often differ from\nthose required by natural selection; and it is clear that the latter\nfactor must at least have reduced use-inheritance to the very minor\nposition of comparative feebleness and harmlessness assigned to it by\nDarwin.\n\nUse-inheritance would be ruinous through causing unequal variation in\nco-operative parts--of which Mr. Spencer may accept his own instances of\nthe jaws and teeth, and the cave-crab's lost eyes and persistent\neye-stalks, as typical examples. That the variation would be unequal\nseems almost self-evident from the varying rapidity and extent of the\neffects of use and disuse on different tissues and on different parts of\nthe general structure. The optic nerve may atrophy in a few months from\ndisuse consequent on the loss of the eye. Some of the bones of the\nrudimentary hind legs of the whale are still in existence after disuse\nfor an enormous period. Evidently use-inheritance could not equally\nmodify the turtle and its shell, or the brain and its skull; and in\nminor matters there would be the same incongruity of effect. Thus, if\nthe molar teeth lengthened from extra use the incisors could not meet.\nUnequal and indiscriminate variation would throw the machinery of the\norganism out of gear in innumerable ways.\n\nUse-inheritance would perpetuate various evils. We are taught, for\ninstance, that it perpetuates short-sight, inferior senses, epilepsy,\ninsanity, nervous disorders, and so forth. It would apparently transmit\nthe evil effects of over-exertion, disuse, hardship, exposure, disease\nand accident, as well as the defects of age or immaturity.\n\nWould it not be better on the whole if each individual took a fresh\nstart as far as possible on the advantageous typical lines laid down by\nnatural selection? Through the long stages of evolution from primaeval\nprotoplasm upwards, such species as were least affected by\nuse-inheritance would be most free to develop necessary but seldom-used\norgans, protective coverings such as shells or skulls, and natural\nweapons, defences, ornaments, special adaptations, and so forth; and\nthis would be an advantage--for survival would obviously depend on the\n_importance_ of a structure or faculty in deciding the struggle for\nexistence and reproduction, and not on the total amount of its using or\nnourishment. If natural selection had on the whole favoured this\nofficious ally and frequent enemy, surely we should find better evidence\nof its existence.\n\nWithout laying undue stress upon the evil effects of use-inheritance, a\ncareful examination of them in detail may at least serve to\ncounter-balance the optimistic _a priori_ arguments for belief in that\nplausible but unproven factor of evolution.\n\nThe benefits derivable from use-inheritance are largely illusory. The\neffects of _use_, indeed, are generally beneficial up to a certain\npoint; for natural selection has sanctioned or evolved organs which\npossess the property or potentiality of developing to the right extent\nunder the stimulus of use or nourishment. But use-_inheritance_ would\ncumulatively alter this individual adaptability, and would tend to fix\nthe size of organs by the average amount of ancestral use or disuse\nrather than by the actual requirements of the individual. Of course\nunder changed conditions involving increased or lessened use of parts it\nmight become advantageous; but even here it may prove a decided\nhindrance to adaptive evolution in some respects as well as an\nunnecessary aid in others. Thus in the case of animals becoming heavier,\nor walking more, it would _lengthen_ the legs although natural selection\nmight require them to be shortened. In the Aylesbury duck and the Call\nduck, if use-inheritance has increased the dimensions of the bones and\ntendons of the leg, natural selection has had to counteract this\nincrease so far as length is concerned, and to effect 8 per cent. of\nshortening besides. If use-inheritance thickens bones without\nproportionally lengthening them, it would hinder rather than help the\nevolution of such structures as the long light wings of birds, or the\nlong legs and neck of the giraffe or crane.\n\n\nVARIED EFFECTS OF USE AND DISUSE.\n\nThe changes which we somewhat roughly and empirically group together as\nthe effects of \"use and disuse\" are of widely diverse character. Thus\nbone, as the physiological fact, thickens under _alternations_ of\npressure (and the consequent increased flow of nourishment), but\natrophies under a steadily continued pressure; so that if the use of a\nbone involved continuous pressure, the effect of such use would be a\npartial or total absorption of that bone. Darwin shows that bone\nlengthens as well as thickens from carrying a greater weight, while\ntension (as seen in sailors' arms, which are used in pulling) appears to\nhave an equally marked effect in shortening bones (_Descent of Man_, p.\n32). Thus different kinds of use may produce opposite results. The\ncumulative inheritance of such effects would often be mischievous. The\nlimbs of the sloth and the prehensile tail of the spider monkey would\ncontinually grow shorter, while the legs of the evolving elephant or\nrhinoceros might lengthen to an undesirable extent. Such cumulative\ntendencies of use-inheritance, if they exist, are obviously well kept\nunder by natural selection.\n\nAlthough the ultimate effect of use is generally growth or enlargement\nthrough increased flow of blood, the first effect usually is a loss of\nsubstance, and a consequent diminution of size and strength. When the\nloss exceeds the growth, use will diminish or deteriorate the part used,\nwhile disuse would enlarge or perfect it. Teeth, claws, nails, skin,\nhair, hoofs, feathers, &c., may thus be worn away faster than they can\nrenew themselves. But this wearing away usually stimulates the repairing\nprocess, and so increases the rate of growth; that is, it will increase\nthe size produced, if not the size retained. Which effect of use does\nuse-inheritance transmit in such cases--the increased rate of growth, or\nthe dilapidation of the worn-out parts? We can hardly suppose that both\nthese effects of use will be inherited. Would shaving destroy the beard\nin time or strengthen it? Will the continued shearing of sheep increase\nor lessen the growth of wool? What will be the ultimate effect of\nplucking geese's quills, and of the eider duck's abstraction of the down\nfrom her breast? If the mutilated parts grow stronger or more\nabundantly, why were the motmot's feathers alleged to be narrowed by the\ninherited effects of ancestral nibbling?\n\nThe \"use\" or \"work\" or \"function\" of muscles, nerves, bones, teeth,\nskin, tendon, glands, ducts, eyes, blood corpuscles, cilia, and the\nother constituents of the organism, is as widely different as the\nvarious parts are from each other, and the effects of their use or\ndisuse are equally varied and complicated.\n\n\nUSE-INHERITANCE IMPLIES PANGENESIS.\n\nHow could the transmission of these varied effects to offspring be\naccounted for? Is it possible to believe, with Mr. Spencer, that the\neffects of use and disuse on the parts of the personal structure are\nsimultaneously registered in corresponding impressions on the seminal\ngerms? Must we not feel, with Darwin apparently,[70] that the _only_\nintelligible explanation of use-inheritance is the hypothesis of\nPangenesis, according to which each modified cell, or physiological\nunit, throws off similarly-modified gemmules or parts of itself, which\nultimately reproduce the change in offspring? If we reject pangenesis,\nit becomes difficult to see how use-inheritance can be possible.\n\n\nPANGENESIS IMPROBABLE.\n\nThe more important and best-known phenomena of heredity do not require\nany such hypothesis, and leading facts (such as atavism, transmission of\nlost parts, and the general non-transmission of acquired characters) are\nso adverse to it that Darwin has to concede that many of the\nreproductive gemmules are atavistic, and that by continuous\nself-multiplication they may preserve a practical \"continuity of\ngerm-substance,\" as Weismann would term it. The idea that the\nrelationship of offspring to parent is one of direct descent is, as\nGalton tells us, \"wholly untenable\"; and the only reason he admits some\nsupplementary traces of pangenesis into his \"Theory of Heredity,\"[71] is\nthat he may thus account for the more or less questionable cases of the\ntransmission of acquired characters. But there appears to be no\nnecessity even for this concession. We ought therefore to dispense with\nthe useless and gratuitous hypothesis that cells multiply by throwing\noff minute self-multiplying gemmules, as well as by the well-known\nmethod of self-division. If pangenesis occurs, the transmission of\nacquired characters ought to be a prominent fact. The size, strength,\nhealth and other good or evil qualities of the cells could hardly fail\nto exercise a marked and corresponding effect upon the size and quality\nof the reproductive gemmules thrown off by those cells. The direct\nevidence tends to show that these free gemmules do not exist.\nTransfusion of blood has failed to affect inheritance in the slightest\ndegree. Pangenesis, with its attraction of gemmules from all parts of\nthe body into the germ-cells, and the free circulation of gemmules in\nthe offspring till they hit upon or are attracted by the particular cell\nor cells, with which alone they can readily unite, seems a less feasible\ntheory and less in conformity with the whole of the facts than an\nhypothesis of germ-continuity which supposes that the development of the\ngerm-plasm and of the successive self-dividing cells of the body\nproceeds from within. Darwin's keen analogy of the fertilization of\nplants by pollen renders development from without conceivable, but as\nthere are no insects to convey gemmules to their destination, each kind\nof gemmule would have to be exceedingly numerous and easily attracted\nfrom amongst an inconceivable number of other gemmules. Arguments\nagainst pangenesis can also be drawn from the case of neuter insects--a\nfact which seems to have escaped Darwin's notice, although he had seen\nhow strongly that case was opposed to the doctrine which is the\nessential basis of the theory of pangenesis.\n\n\nSPENCER'S EXPLANATION OF USE-INHERITANCE.\n\nMr. Spencer's explanation of the inheritance of the effects of use and\ndisuse (p. 36) is that \"while generating a modified _consensus_ of\nfunctions and of structures, the activities are at the same time\nimpressing this modified _consensus_ on the sperm-cells and germ-cells\nwhence future individuals are to be produced\"--a proposition which reads\nmore like metaphysics than science. Difficult to understand or believe\nin ordinary instances, such _consensus_-inheritance seems impossible in\ncases like that of the hive-bee. Can we suppose that the _consensus_ of\nthe activities of the working bee impresses itself on the sperm-cells\nof the drones and on the germ-cells of the carefully secluded queen?\nBuechner thinks so, for he says: \"Although the queens and drones do not\nnow work, yet the capacities inherited from earlier times still remain\nto them, especially to the former, and are kept alive and fresh by the\nimpressions constantly made upon them during life, and they are thus in\na position to transmit them to posterity.\" Surely it is better to\nabandon a cherished theory than to be compelled to defend it by\nexplanations which are as inconsistent as they are inadequate. New\ncapacities are developed as well as old ones kept fresh. The massacre or\nexpulsion of the drones would have to impress itself on the germ-cells\nof an onlooking queen, and the imprisonment of the queen on the\nsperm-cells of the drones--and in such a way, moreover, as to be\nafterwards developed into action in the neuters only. And\nuse-inheritance all the while is being thoroughly overpowered by\nimpression-inheritance--by the full transmission of that which is merely\nseen in others! If such a law prevails, one may feel cold because an\nancestor thought of the frosty Caucasus. None of this absurdity would\narise if it were clearly seen that a parent is only a trustee--that\ntransmission and development are perfectly distinct--that parental\nmodifications are irrelevant to those transmitted to offspring.\n\n\nFOOTNOTES:\n\n[67] _Essays on Heredity_, p. 104. Weismann's theory is clear, simple\nand convenient, but incomplete; for, unlike Darwin's theory of\npangenesis, it scarcely attempts any real explanation of the extremely\ncomplex potentialities possessed by the reproductive elements. Perhaps\nwe might retain Darwin's self-multiplying gemmules without supposing\nthem to be thrown off by the cells, which will no longer be credited\nwith _two_ modes of multiplication. These minute germs or gemmules may\nhave been evolved by natural selection playing upon the sample germs\nthat achieve development; and they may exist either separately, or\n(preferably but perhaps not invariably) in aggregates to form Weismann's\ngerm-plasm.\n\n[68] _Contemporary Review_, Dec., 1875, p. 88.\n\n[69] _Variation of Animals and Plants under Domestication_, ii. 286.\n\n[70] _Variation of Animals and Plants under Domestication_, ii. 388,\n398, 367; _Life and Letters_, iii. 44.\n\n[71] _Contemporary Review_, Dec., 1875, pp. 94, 95.\n\n\n\n\nCONCLUSIONS.\n\n\nUSE-INHERITANCE DISCREDITED AS UNNECESSARY, UNPROVEN, AND IMPROBABLE.\n\nGeneral experience teaches that acquired characters are not usually\ninherited; and investigation shows that the apparent exceptions to this\ngreat rule are probably fallacious. Even the alleged instances of\nuse-inheritance culled by such great and judicious selectors as Darwin\nand Spencer break down upon examination; for they can be better\nexplained without use-inheritance than with it. On the other hand, the\nadverse facts and considerations are almost strong enough to prove the\nactual non-existence of such a law or tendency. There is no need to\nundertake the apparently impossible task of demonstrating an absolute\nnegative. It will be enough to ask that the Lamarckian factor of\nuse-inheritance shall be removed from the category of accredited factors\nof evolution to that of unnecessary and improbable hypotheses. The main\nexplanation or source of the fallacy may be found in the fact that\nnatural selection frequently imitates some of the more obvious effects\nof use and disuse.\n\n\nMODERN RELIANCE ON USE-INHERITANCE MISPLACED.\n\nModern philanthropy--so far at least as it ever studies ultimate\nresults--constantly relies on this ill-founded belief as its\njustification for ignoring the warnings of those who point out the\nultimately disastrous results of a systematic defiance or reversal of\nthe great law of natural selection. This reliance finds strong support\nin Mr. Spencer's latest teachings, for he holds that the inheritance of\nthe effects of use and disuse takes place universally, and that it is\nnow \"the chief factor\" in the evolution of civilized man (pp. 35, 74,\niv)--natural selection being quite inadequate for the work of\nprogressive modification. Practically he abandons the hope of evolution\nby natural selection, and substitutes the ideal of a nation being\n\"modified _en masse_ by transmission of the effects\" of its institutions\nand habits. Use-inheritance will \"mould its members far more rapidly and\ncomprehensively\" than can be effected by the survival of the fittest\nalone.\n\nBut could we rely upon the aid of use-inheritance if it really were a\nuniversal law and not a mere simulation of one? Let us consider some of\nthe features of this alleged factor of evolution, seeing that it is\nhenceforth to be our principal means of securing the improvement of our\nspecies and our continued adaptation to the changing conditions of a\nprogressive civilization.\n\nIt is curiously uncertain and irregular in its action. It diminishes or\nabolishes some structures (such as jaws or eyes) without correspondingly\ndiminishing or abolishing other equally disused and closely related\nparts (such as teeth, or eye-stalks). It thickens ducks' leg-bones while\nallowing them to shorten. It shortens the disused wing-bones of ducks\nand the leg-bones of rabbits while allowing them to thicken; and yet in\nother cases it greatly reduces the thickness of bones without shortening\nthem. It transmits tameness most powerfully in an animal which usually\ncannot acquire it. It aids in webbing the feet of water-dogs, but fails\nto web the feet of the water-hen or to remove the web in the feet of\nupland geese.[72] It allows the disused fibula to retain a potentiality\nof development fully equal to that possessed by the long-used tibia. It\nlengthens legs because they are used in supporting the body, and\nshortens arms because they are used in pulling. Whether it enlarges\nbrain if used in one way and diminishes it if used in another, we cannot\ntell; but it must obviously deaden nervous sensibilities in some cases\nand intensify them in others. It enlarges hands long before they are\nused, and thickens soles long before the time for walking on them. At\nthe same time, as if by an oversight, it so delays its transmission of\nthe habit of walking on these thickened soles, that the gradual and\ntedious acquisition of the non-transmitted habit costs the infant much\ntime and trouble and often some pain and danger. Yet where aided by\nnatural selection, as with chickens and foals, it transmits the habit in\nwonderful perfection and at a remarkably early date. It transmits new\npaces in horses in a single generation, but fails to perpetuate the\nsongs of birds. It modifies offspring like parents, and yet allows the\nformation of two reproductive types in plants, and of two or more types\nwidely different from the parents in some of the higher insects. It is\nsaid to be indispensable for the co-ordinated development of man and the\ngiraffe and the elk, but appears to be unnecessary for the evolution and\nthe maintenance of wonderful structures and habits and instincts in a\nthousand species of ants and bees and termites. It is the only possible\nmeans of complex evolution and adaptation of co-operative parts, and yet\nin Mr. Spencer's most representative case it renders such important\nparts as teeth and jaws unsuited for each other, and is said to ruin the\nteeth by the consequent overcrowding and decay. It survives amidst a\ngeneral \"lack of recognised evidence,\" and only seems to act usefully\nand healthily and regularly in quarters where it can least easily be\ndistinguished from other more powerful and demonstrable factors of\nevolution. So little does it care to display its powers where they would\nbe easily verifiable as well as useful that practical breeders ignore\nit. So slight is its independent power that it seems to allow natural\nselection or sexual selection or artificial selection to modify\norganisms in sheer defiance of its utmost opposition, just as readily as\nthey modify organisms in other directions with its utmost help. If it\npartially perpetuates and extends the pecked-out indentations in the\nmotmot's tail feathers, it on the other hand fails to transmit the\nslightest trace of mutilation in an almost infinite number of ordinary\ncases, and even where the mutilation is repeated for a hundred\ngenerations; and it apparently repairs rather than transmits the\nordinary and oft-repeated losses caused by plucking hair, down and\nfeathers, and the wear and tear of claws, teeth, hoofs and skin.\n\nIt is often mischievous as well as anomalous in its action. Under\ncivilization with its division of labour, the various functions of mind\nand body are very unequally exercised. There is overwork or misuse of\none part and disuse and neglect of others, leading to the partial\nbreakdown or degeneration of various organs and to general deterioration\nof health through disturbed balance of the constitution. The brain, or\nrather particular parts of it, are often over-stimulated, while the body\nis neglected. In many ways education and civilization foster nervousness\nand weakness, and undermine the rude natural health and spirits of the\nhuman animal. Alcohol, tobacco, tea, coffee, extra brain work, late\nhours, dissipation, overwork, indoor life, division of labour,\npreservation of the weak, and many other causes, all help to injure the\nmodern constitution; so that the prospect of cumulative intensification\nof these evils by the additional influence of use-inheritance is not an\nencouraging one. It is true that modern progress and prosperity are\nimproving the people in various respects by their direct action; but if\nuse-inheritance has any share in effecting this improvement it must also\ntransmit increased wants and more luxurious habits, together with such\nevils as have already been referred to. As depicted by its defenders,\nuse-inheritance transmits evils far more powerfully and promptly than\nbenefits. It transmits insanity and shattered nerves rather than the\nhealthy brain which preceded the breakdown. It perpetuates, and\ncumulatively intensifies, a deterioration in the senses of civilized\nmen, but it fails to perpetuate the rank vigour of various plants when\ntoo well nourished, or the flourishing condition of various animals when\ntoo fat or when tamed. It already transmits the short-sight caused by so\nmodern an art as watchmaking, but so fails to transmit the\nlong-practised art of seeing (as it does of walking and talking) that\nvision is worse than useless to a man until he gradually acquires the\nnecessary but non-transmitted associations of sensation and idea by his\nown experience. In a well-known case, a blind man on gaining his sight\nby an operation said that \"all objects seemed to touch his eyes, as what\nhe felt did his skin\"--so little had the universal experience of\ncountless ages impressed itself on his faculties. Under normal healthy\nconditions use-inheritance is so slow in its action that \"several\ngenerations\" must elapse before it produces any appreciable effect, and\nthen that effect is only precisely what selection might be expected to\nbring about without its aid. Strong for evil and slow for good, it can\nconvey epilepsy promptly in guinea pigs, but transmits the acquirements\nof genius so poorly that our best student of the heredity of genius has\nto account for the frequent and remarkable deterioration of the\noffspring by a theory which is strongly hostile to use-inheritance. It\nwould tend to make organisms unworkable by the excessive differences in\nits rate and manner of action on co-operative parts, and by adapting\nthese parts to the total amount of nourishment received rather than to\noccasional necessity or actual usefulness. It would tend to stereotype\nhabits and convert reason into instinct.\n\nHow then can we rely upon use-inheritance for the improvement of the\nrace? Even if it is not a sheer delusion, it may be more detrimental as\na positive evil than it is advantageous as an unnecessary benefit; and\nas a normal modifying agent it is miserably weak and untrustworthy in\ncomparison with the powerful selective influences by which nature and\nsociety continually and inevitably affect the species for good or for\nevil. The effects of use and disuse--rightly directed by education in\nits widest sense--must of course be called in to secure the highly\nessential but nevertheless _superficial, limited, and partly deceptive_\nimprovement of individuals and of social manners and methods; but as\nthis artificial development of already existing potentialities does not\ndirectly or readily tend to become congenital, it is evident that some\nconsiderable amount of natural or artificial selection of the more\nfavourably varying individuals will still be the only means of securing\nthe race against the constant tendency to degeneration which would\nultimately swallow up all the advantages of civilization. The selective\ninfluences by which our present high level has been reached and\nmaintained may well be modified, but they must not be abandoned or\nreversed in the rash expectation that State education, or State feeding\nof children, or State housing of the poor, or any amount of State\nsocialism or public or private philanthropy, will prove permanently\nsatisfactory substitutes. If ruinous deterioration and other more\nimmediate evils, are to be avoided, the race must still be to the swift\nand the battle to the strong. The healthy Individualism so earnestly\nchampioned by Mr. Spencer must be allowed free play. Open competition,\nas Darwin teaches, with its survival and multiplication of the fittest,\nmust be allowed to decide the battle of life independently of a foolish\nbenevolence that prefers the elaborate cultivation and multiplication of\nweeds to the growth of corn and roses. We are trustees for the countless\ngenerations of the future. If we are wise we shall trust to the great\nruling truths that we assuredly know, rather than to the seductive\nclaims of an alleged factor of evolution for which no satisfactory\nevidence can be produced.\n\n\nTHE END.\n\nRICHARD CLAY AND SONS, LIMITED, LONDON AND BUNGAY.\n\n\nFOOTNOTES:\n\n[72] Professor Romanes had casts made of the feet of upland geese, and\ncould not detect any diminution as compared with the web of other geese\nin relation to the toes.\n\n\n\n\nNATURE SERIES.\n\n\nPOPULAR LECTURES AND ADDRESSES ON VARIOUS SUBJECTS IN PHYSICAL SCIENCE.\nBy Sir WILLIAM THOMSON, D.C.L. LL.D., F.R.S.E, Fellow of St. Peter's\nCollege, Cambridge, and Professor of Natural Philosophy in the\nUniversity of Glasgow. With Illustrations. 3 vols. Crown 8vo. Vol. 1.\nCONSTITUTION OF MATTER. 6_s._\n\nON THE ORIGIN AND METAMORPHOSES OF INSECTS. By Sir JOHN LUBBOCK, Bart.,\nF.R.S., M.P., D.C.L., LL.D. With numerous Illustrations. 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