Darwin, and After Darwin, Volume 2 of 3 / Post-Darwinian Questions: Heredity and Utility

FOOTNOTES

[1] Part I, pp. 253-256.

[2] Contributions to the Theory of Natural Selection, p. 47.

[3] So far as we shall be concerned with them throughout this treatise, the "Lamarckian factors" consist in the supposed transmission of acquired characters, whether the latter be due to the direct influence of external conditions of life on the one hand, or to the inherited effects of use and disuse on the other. For the phrase "inherited effects of use and disuse," I shall frequently employ the term "use-inheritance," which has been coined by Mr. Platt Ball as a more convenient expression.

[4] Origin of Species, 6th ed. p. 8.

[5] Variation &c. 2nd ed. ii. p. 280.

[6] Variation &c. ii. p. 367.

[7] Origin of Species, p. 176.

[8] This, to the best of my judgement, is the fairest extract that I can give of Mr. Wallace's most recently published opinions on the points in question. [In particular as regards (a) see Darwinism pp. 435-6.] But with regard to some of them, his expression of opinion is not always consistent, as we shall find in detail later on. Besides, I am here taking Mr. Wallace as representative of the Neo-Darwinian school, one or other prominent member of which has given emphatic expression to each of the above propositions.

[9] Life and Letters, vol. iii. pp. 72 and 75.

[10] Take, for example, the following, which is a fair epitome of the whole:—"I believe that this is the simplest mode of stating and explaining the law of variation; that some forms acquire something which their parents did not possess; and that those which acquire something additional have to pass through more numerous stages than their ancestors; and those which lose something pass through fewer stages than their ancestors; and these processes are expressed by the terms 'acceleration' and 'retardation'" (Origin of the Fittest, pp. 125, 226, and 297). Even if this be "the simplest mode of stating the law of variation," it obviously does nothing in the way of explaining the law.

[11] Floral Structures (Internat. Sc. Ser. lxiv. 1888): The Making of Flowers (Romance of Science Ser. 1891); and Linn. Soc. Papers 1893-4.

[12] "The law of correlation," and the "laws of growth," he does recognize; and shows that they furnish an explanation of the origin of many characters, which cannot be brought under "the law of utility."

[13] Natural Selection and Tropical Nature, p. 205; 1891.

[14] Ibid. pp. 197-8.

[15] For an excellent discussion on the ontogeny of the child in this connexion, see Some Laws of Heredity, by Mr. S. S. Buckman, pp. 290, et seq. (Proc. Cotteswold Nat. Field Club, vol. x. p. 3, 1892).

[16] loc. cit. p. 198.

[17] For a discussion of this remarkable case, see Mental Evolution in Animals, pp. 222-3. It appears to me that if Mr. Wallace's argument from the "latent capacities of the voice of Man" is good for anything, a fortiori it must be taken to prove that, in the case of the Parrot, "the organ has been prepared in anticipation" of the amusement which the cultivation of its latent capacities arouses in "civilized man."

[18] Descent of Man, 1st Ed. ch. xx. (Trans. Dev. Assoc. for Science, 1890).

[19] The late Prof. Moseley informed me that, during his voyage on the Challenger, he had seen many men whose backs were well covered with hair.—For an excellent discussion of the whole question, chiefly in the light of embryology, see the paper by Buckman already alluded to, pp. 280-289. Also, for an account of an extraordinary hairy race of men, see Alone with the Hairy Ainu, by A. H. Savage Landor, 1893.

[20] E.g. "The special faculties we have been discussing clearly point to the existence in man of something which he has not derived from his animal progenitors—something which we may best refer to as being of a spiritual essence or nature, capable of progressive development under favourable conditions. On the hypothesis of this spiritual nature, superadded to the animal nature of man, we are able to understand much that is otherwise mysterious or unintelligible in regard to him, especially the enormous influence of ideas, principles, and beliefs over his whole life and action. Thus alone can we understand the constancy of the martyr, the unselfishness of the philanthropist, the devotion of the patriot, the enthusiasm of the artist, and the resolute and persevering search of the scientific worker after nature's secrets. Thus we may perceive that the love of truth, the delight in beauty, the passion for justice, and the thrill of exultation with which we hear of any act of courageous self-sacrifice, are the workings within us of a higher nature which has not been developed by means of the struggle for material existence." (Darwinism, p. 474.) I have quoted this whole paragraph, because it is so inconsistent with the rest of Mr. Wallace's system that a mere epitome of it might well have been suspected of error. Given an intellectual being, howsoever produced, and what is there "mysterious or unintelligible" in "the enormous influence of ideas, principles, and beliefs over his whole life and action"? Or again, if he be also a social being, what is the relevancy of adducing "the constancy of the martyr," "the unselfishness of the philanthropist," "the devotion of the patriot," "the love of truth," "the passion for justice," "the thrill of exultation when we hear of any act of courageous self-sacrifice," in evidence against the law of utility, or in order to prove that a "nature" thus endowed has "not been developed by means of the struggle for existence," when once this struggle has been transferred from individuals to communities? The whole passage reads like an ironical satire in favour of "Darwinism," rather than a serious argument against it.

[21] See Proc. Zool. Soc. June 4, 1889, for an account of the performances in this respect of the Chimpanzee "Sally." Also, for some remarks on the psychology of the subject, in Mental Evolution in Man, p. 215. I should like to take this opportunity of stating that, after the two publications above referred to, this animal's instruction was continued, and that, before her death, her "counting" extended as far as ten. That is to say, any number of straws asked for from one to ten would always be correctly given.

[22] In Prof. Lloyd Morgan's Animal Life and Intelligence there is an admirable discussion on this subject, which has been published since the above was written. The same has to be said of Weismann's Essay on Music, where much that I have here said is anticipated. With the views and arguments which Mr. Mivart has forcibly set forth I have already dealt to the best of my ability in a work on Mental Evolution in Man.

[23] American Naturalist, xxii. pp. 201-207.

[24] It is almost needless to say that besides the works mentioned in this chapter, many others have been added to the literature of Darwinism since Darwin's death. But as none of these profess to contain much that is original, I have not thought it necessary to consider any of them in this merely general review of the period in question. In subsequent chapters, however, allusions will be made to those among them which I deem of most importance.

[Since this note was written and printed the following works have been published to which it does not apply: Animal Life and Intelligence, by Professor Lloyd Morgan; The Colours of Animals, by Professor Poulton; and Materials for the Study of Variation, by Mr. Bateson. All these works are of high value and importance. Special reference should also be made to Professor Weismann's Essays.]

[25] Originally, Weismann's further assumption as to the perpetual stability of germ-plasm, "since the first origin of sexual reproduction," was another very important point of difference, but this has now been withdrawn.

[26] I say "mainly formed anew," and "for the most part interrupted," because even Darwin's theory does not, as is generally supposed, exclude the doctrine of Continuity in toto.

[27] Theory of Heredity (Journ. Anthrop. Inst. 1875, p. 346).

[28] Mr. Platt Ball has, indeed, argued that "use-inheritance would often be an evil," since, for example, "the condyle of the human jaw would become larger than the body of the jaw, because as the fulcrum of the lever it receives more pressure"; and similarly as regards many other hypothetical cases which he mentions. (The Effects of Use and Disuse, pp. 128-9 et seq.) But it is evident that this argument proves too much. For if the effects of use and disuse as transmitted to progeny would be an evil, it could only be because these effects as they occur in the parents are an evil—and this they most certainly are not, being, on the contrary and as a general rule, of a high order of adaptive value. Moreover, in the race, there is a superadded agency always at work, which must effectually prevent any undue accumulation of these effects—namely, natural selection, which every Darwinist accepts as a controlling principle of all or any other principles of change. Therefore, if, as first produced in the life-time of individuals, the effects of use and disuse are not injurious, much less can they become so if transmitted through the life-time of species. Again, Mr. Wallace argues that, even supposing use-inheritance to occur, its adapting work in the individual can never extend to the race, seeing that the natural selection of fortuitous variations in the directions required must always produce the adaptations more quickly than would be possible by use-inheritance. This argument, being one of more weight, will be dealt with in a future chapter.

[29] Variation under Domestication, ii. 392.

[30] In subsequent chapters, especially devoted to the question (i.e. Section II), the validity of this assumption will be considered on its own merits.

[31] I say "the followers of Weismann," because Weismann himself, with his clear perception of the requirements of experimental research, expressly states the above considerations, with the conclusions to which they lead. Nevertheless, he is not consistent in his utterances upon this matter; for he frequently expresses himself to the effect, "that the onus probandi rests with my opponents, and therefore they ought to bring forward actual proofs" (Essays, i. p. 390). But, as above shown, the onus rests as much with him as with his opponents; while, even if his opponents are right, he elsewhere recognizes that they can bring "actual proofs" of the fact only as a result of experiments which must take many years to perform.

[32] Note A.

[33] For a fair and careful statement of the present balance of authoritative opinion upon the question, see H. F. Osborn, American Naturalist, 1892, pp. 537-67.

[34] [The above paragraph is allowed to remain exactly as Mr. Romanes left it. Chapters V and VI were however not completed. See note appended to Preface. C. Ll. M.

[35] See, especially, his excellent remarks on this point, Contemp. Rev. Sept. 1893.

[36] There is now an extensive literature within this region. The principal writers are Cope, Scott and Osborn. Unfortunately, however, the facts adduced are not crucial as test-cases between the rival theories—nearly all of them, in fact, being equally susceptible of explanation by either.

[37] For another and better illustration more recently published by Mr. Spencer, see The Inadequacy of Natural Selection, p. 22.

[38] Essays on Heredity, vol. i. p. 389.

[For further treatment of the subject under discussion see Weismann, The All-sufficiency of Natural Selection (Contemp. Rev. Sept. and Oct. 1893), and The Effect of External Influences upon Development. "Romanes Lecture" 1894, and Spencer, Weismannism once more (Cont. Rev. Oct. 1894). C. Ll. M.]

[39] Variation, &c., vol. ii. p. 206.

[40] E. g. Origin of Species, p. 178.

[41] Darwinism, p. 418.

[42] Nature, vol. xliii. pp. 410, 557; vol. xliv. pp. 7, 29. I say "adopted," because I had objected to his quoting the analogy of artificial selection, and stated, as above, that the only way to meet Mr. Spencer's "difficulty" was to deny the fact of co-adaptation as ever occurring in any case. It then appeared that Professor Meldola agreed with me as to this. But I do not yet understand why, if such were his view, he began by endorsing Mr. Wallace's analogy from artificial selection—i. e. confusing the case of co-adaptation with that of the blending of adaptations. If any one denies the fact of co-adaptation, he cannot assist his denial by arguing the totally different fact that adaptations may be blended by free intercrossing; for this latter fact has never been questioned, and has nothing to do with the one which he engaged in disputing.

[43] It may be said, with regard to this particular reflex, that it may perhaps be, so to speak, a mechanical accident, arising from the contiguity of the sensory and motor roots in the cord. But as this suggestion cannot apply to other reflexes presently to be adduced, it need not be considered.

[44] Of course it will be observed that the question is not with regard to the development of all the nerves and muscles concerned in this particular process. It is as to the development of the co-ordinating centres, which thus so delicately respond to the special stimuli furnished by variations of angle to the horizon. And it is as inconceivable in this case of reflex action, as it is in almost every other case of reflex action, that the highly specialized machinery required for performing the adaptive function can ever have had its origin in the performance of any other function. Indeed, a noticeable peculiarity of reflex mechanisms as a class is the highly specialized character of the functions which their highly organized structures subserve.

[45] We meet with a closely analogous reflex mechanism in brainless vertebrata of other kinds; but these do not furnish such good test cases, because the possibility of natural selection cannot be so efficiently attenuated. The perching of brainless birds, for instance, at once refers us to the roosting of sleeping birds, where the reflex mechanism concerned is clearly of high adaptive value. Therefore such a case is not available as a test, although the probability is that birds have inherited their balancing mechanisms from their sauropsidian ancestors, where it would have been of no such adaptive importance.

[46] PflÜger's Archiv, Bd. xx. s. 23 (1879).

[47] Brain, part xlviii, pp. 516-19 (1889).—There is still better proof of this in the case of certain rodents. For instance, observing that rats and mice are under the necessity of very frequently scratching themselves with their hind-feet, I tried the experiment of removing the latter from newly-born individuals—i.e. before the animals were able to co-ordinate their movements, and therefore before they had ever even attempted to scratch themselves. Notwithstanding that they were thus destitute of individual experience with regard to the benefit of scratching, they began their scratching movements with their stumps as soon as they were capable of executing co-ordinated movements, and afterwards continued to do so till the end of their lives with as much vigour and frequency as unmutilated animals. Although the stumps could not reach the seats of irritation which were bent towards them, they used to move rapidly in the air for a time sufficient to have given the itching part a good scratch, had the feet been present—after which the animals would resume their sundry other avocations with apparent satisfaction. These facts showed the hereditary response to irritation by parasites to be so strong, that even a whole life-time's experience of its futility made no difference in the frequency or the vigour thereof.

[48] For details of his explanation of this particular case, for which I particularly inquired, see Mental Evolution in Animals, pp. 301-2.

[49] Note B.

[50] For fuller treatment see Mental Evolution in Animals, pp. 274-285, 378-379, 381-383.

[51] For an excellent essay on the deleterious character of early forms of religion from a biological point of view, see the Hon. Lady Welby, An Apparent Paradox in Mental Evolution (Journ. Anthrop. Inst. May 1891).

[52] Essays, i. p. 93.

[53] See Mental Evolution in Animals, pp. 377-8.

[54] [See H. Spencer, The Inadequacy of Natural Selection, A Rejoinder to Professor Weismann, Contemp. Rev. 1893; and Weismannism once more, Ibid. Oct. 1894; Weismann, The All-sufficiency of Natural Selection, Ibid. 1893; and The Effect of External Influences upon Development, "Romanes Lecture" 1894: also Neuter Insects and Lamarckism, W. Platt Ball, Natural Science, Feb. 1894, and Neuter Insects and Darwinism, J. T. Cunningham, Ibid. April 1894. C. Ll. M.]

[55] Variation of Plants and Animals, vol. ii. p. 289.

[56] Ibid. p. 346.

[57] Essays, i. p. 90.

[58] Nature, vol. ix. pp. 361-2, 440-1; and vol. x. p. 164.

[59] Appendix I.

[60] For a fuller statement of Mr. Galton's theory of Heredity, and its relation to Weismann's, see An Examination of Weismannism.

[61] For a fuller explanation of the important difference between the mere cessation and the actual reversal of selection, see Appendix I.

[62] Animal Life, International Scientific Series, vol. xxxi.

[63] The experiments of Galton and Weismann upon this subject are nugatory, as will be shown later on. But since the above was written an important research has been published by Mr. Cunningham, of the Marine Biological Association. For a full account I must refer the reader to his forthcoming paper in the Philosophical Transactions. The following is his own statement of the principal results:—

"A case which I have myself recently investigated experimentally seems to me to support very strongly the theory of the inheritance of acquired characters, I have shown that in normal flat-fishes, if the lower side be artificially exposed to light for a long time, pigmentation is developed on that side; but when the exposure is commenced while the specimens are still in process of metamorphosis, when pigment-cells are still present on the lower side, the action of light does not prevent the disappearance of these pigment-cells. They disappear as in individuals living under normal conditions, but after prolonged exposure pigment-cells reappear. The first fact proves that the disappearance of the pigment-cells from the lower side in the metamorphosis is an hereditary character, and not a change produced in each individual by the withdrawal of the lower side from the action of light. On the other hand, the experiments show that the absence of pigment-cells from the lower side throughout life is due to the fact that light does not act upon that side, for, when it is allowed to act, pigment-cells appear. It seems to me the only reasonable conclusion from these facts is, that the disappearance of pigment-cells was originally due to the absence of light, and that this change has now become hereditary. The pigment-cells produced by the action of light on the lower side are in all respects similar to those normally present on the upper side of the fish. If the disappearance of the pigment-cells were due entirely to a variation of the germ-plasm, no external influence could cause them to reappear, and, on the other hand, if there were no hereditary tendency, the colouration of the lower side of the flat-fish when exposed would be rapid and complete."—Natural Science, Oct. 1893.

[64] For Professor Weismann's statement of and discussion of these results see Essays, vol. i. p. 313.

[65] Oesterreichische medicinische JahrbÜcher, 1875, 179.

[66] Loc. cit.

[67] Essays, vol. i. p. 315.

[68] Les fonctions du Cerveau, p. 102.

[69] Essays, vol. i. p. 82.

[70] As Weismann gives an excellent abstract of all the alleged facts up to date (Essays, vol. i. pp. 319-324), it is needless for me to supply another, further than that which I have already made from Brown-SÉquard.

[71] Examination of Weismannism, p. 83.

[72] Examination of Wiesmannism, p. 93.

[73] Ibid. p. 153.

[74] Origine des Plantes Domestiques, dÉmontrÉe par la culture du Radis Sauvage (Paris, 1869).

[75] Journl. Agric. Soc. 1848.

[76] Rev. GÉn. de Bot. tom. ii. p. 64.

[77] I am indebted to the Rev. G. Henslow for the references to these cases. This and the passages which follow are quoted from his letters to me.

[78] Gardener's Chronicle, May 31, 1890, p. 677.

[79] Since the above was written Professor Weismann has advanced, in The Germ-plasm, a suggestion very similar to this. It is sufficient here to remark, that nearly all the facts and considerations which ensue in the present chapter are applicable to his suggestion, the essence of which is anticipated in the above paragraph.

[80] It also serves to show that Weismann's newer doctrine of similar "determinants" occurring both in the germ and in the somatic tissues is a doctrine which cannot be applied to rebut this evidence of the transmission of acquired characters in plants. Therefore even its hypothetical validity as applied by him to explain the seasonal variation of butterflies is rendered in a high degree dubious.

[81] [See note appended to Preface. C. LI. M.]

[82] Proc. R. S. 1871.

[83] Proc. R. S. 1890, vol. xlviii. p. 457. It should be stated that the authors do not here concern themselves with any theory of heredity.

[84] See note appended to Preface. C. Ll. M.

[85] E.g. "The supposed transmission of this artificially produced disease (epilepsy) is the only definite instance which has been brought forward in support of the transmission of acquired characters."—Essays, p. 328.

[86] For a full treatment of Professor Huxley's views upon this subject, see Appendix II.

[87] Professor Huxley's views upon this matter are quoted in extenso in Appendix II.

[88] Geographical Distribution of the Family Charadriidae, p. 19.

[89] Contributions to the Theory of Natural Selection, p. 47 (1870); republished in 1892.

[90] Origin of Species, p. 70: italics mine.

[91] Darwinism, p. 137: italics mine.

[92] Origin of Species, p. 72: Mr. Wallace himself quotes this passage (Darwinism, p. 141); but says with regard to it "the important word 'all' is probably an oversight." In the Appendix (II), on Darwin's views touching the doctrine of utility I adduce a number of precisely equivalent passages, derived from all his different works on evolution, and every one of them presenting "the important word 'all.'"

[93] See Introductory Chapter, p. 20.

[94] Darwinism, p. 138.

[95] Origin of Species, p. 176: italics mine, as also in the following.

[96] Var. vol. ii. p. 250.

[97] Variation, &c. vol. i. pp. 78-79.

[98] Darwinism, pp. 139-40.

[99] Mr. Wallace deems the concluding words "rather confident." I was not, however, before aware that he extended his a priori views on utility to domesticated varieties which are bred for the slaughter-house. If he now means to indicate that these appendages are possibly due to natural selection, he is surely going very far to save his a priori dogma; and in the case next adduced will have to go further still.

[100] Origin of Species, pp. 122-3.

[101] Darwinism, p. 140.

[102] In the next paragraph Mr. Wallace says that the appendages in question "are apparently of the same nature as the 'sports' that arise in our domesticated productions, but which, as Mr. Darwin says, without the aid of selection would soon disappear." But I cannot find that Mr. Darwin has made any such statement: what he does say is, that whether or not a useless peculiarity will soon disappear without the aid of selection depends upon the nature of the causes which produce it. If these causes are of a merely transitory nature, the peculiarity will also be transitory; but if the causes be constant, so will be the result. Again, the point to be noticed about this "sport" is, that, unlike what is usually understood by a "sport," it affects a whole race or breed, is transmitted by sexual propagation, and has already attained so definite a size and structure, that it can only be reasonably accounted for by supposing the continued operation of some constant cause. This cause can scarcely be correlation of growth, since closely similar appendages are often seen in so different an animal as a goat. Here, also, they run in breeds or strains, are strongly inherited, and more "constant," as well as more "symmetrical" than they are in pigs. This, at all events, is the account I have received of them from goat-breeders in Switzerland.

[103] Darwin, Variation, &c., vol. i. pp. 92-4.

[104] Ibid. p. 94.

[105] Darwin, Variation, &c. vol. i. p. 94.

[106] Should it be objected that useless characters, according to my own view of the Cessation of Selection, ought to disappear, and therefore cannot be constant, the answer is evident. For, by hypothesis, it is only those useless characters which were at one time useful that disappear under this principle. Selection cannot cease unless it was previously present—i.e. save in cases where the now useless character was originally due to selection. Hence, in all cases where it was due to any other cause, the useless character will persist at least as long as its originating cause continues to operate. And even after the latter (whatever it may be) has ceased to operate, the useless character will but slowly degenerate, until the eventual failure of heredity causes it to disappear in toto—long before which time it may very well have become a genetic, or some higher, character.

[107] Variation, &c. vol. i. p. 340.

[108] Variation, &c. vol. ii. p. 271.

[109] Since the above paragraphs have been in type, the Rev. G. Henslow has published his Linnaean Society papers which are mentioned in the introductory chapter, and which deal in more detail with this subject, especially as regards the facies of desert floras.

[110] Trans. Entom. Soc. 1889, part i. p. 79 et seq.

[111] Variation, &c. vol. i. p. 40.

[112] Variation, &c. vol. i. p. 40.

[113] Variation, &c. vol. i. p. 120.

[114] See especially, Koch, Die Raupen und Schmetterling der Wetterau, and Die Schmetterling des SÜdwestlichen Deutschlands, whose very remarkable results of numerous and varied experiments are epitomized by Eimer, Organic Evolution, Eng. Trans. pp. 147-153; also Poulton, Trans. Entom. Soc. 1893.

[115] Mivart, On Truth, p. 378.

[116] Cockerell, Nature, vol. xli. p. 393.

[117] Darwinism, pp.[typo: period missing in scan] 296-7: italics mine.

[118] Nature, vol. xxxiii. p. 100.

[119] Divergent Evolution through Cumulative Segregation, Linn. Journ. Zoology, vol. xx. p. 215.

[120] Habit and Intelligence, p. 241.

[121] Allusion may here again be made to the case of the niata cattle. For here is a case where a very extreme variety is certainly not unstable, nor produced in varying proportions from the parent form. Moreover, as we have seen in the preceding chapter, this almost monstrous variety most probably originated as an individual sport—being afterwards maintained and multiplied for a time by artificial selection. Now, whether or not this was the case, we can very well see that it may have been. Hence it will serve to illustrate another possibility touching the origin and maintenance of useless specific characters. For what is to prevent an individual congenital variation of any kind (provided it be not harmful) from perpetuating itself as a "varietal," and eventually, should offspring become sufficiently numerous, a "specific character"? There is nothing to prevent this, save panmixia, or the presence of free intercrossing. But, as we shall see in the next division of this treatise, there are in nature many forms of isolation. Hence, as often as a small number of individuals may have experienced isolation in any of its forms, opportunity for perpetuation will have been given to any congenital variations which may happen to arise. Should any of these be pronounced variations, it would afterwards be ranked as a specific character. I do not myself think that this is the way in which indifferent specific characters usually originate. On the contrary, I believe that their origin is most frequently due to the influence of isolation on the average characters of the whole population, as briefly stated in the text. But here it seems worth while to notice this possibility of their occasionally arising as merely individual variations, afterwards perpetuated by any of the numerous isolating conditions which occur in nature. For, if this can be the case with a varietal form so extreme as to border on the monstrous, much more can it be so with such minute differences as frequently go to constitute specific distinctions. It is the business of species-makers to search out such distinctions, no matter how trivial, and to record them as "specific characters." Consequently, wherever in nature a congenital variation happens to arise, and to be perpetuated by the force of heredity alone under any of the numerous forms of isolation which occur in nature, there will be a case analogous to that of the niata cattle.

[122] It is almost needless to say that by a definition as "logical" is meant one which, while including all the differentiae of the thing defined, excludes any qualities which that thing may share in common with any other thing. But by definitions as "logically possible" I mean the number of separate definitions which admit of being correctly given of the same thing from different points of view. Thus, for instance, in the present case, since the above has been in type the late M. Quatrefages' posthumous work on Darwin et ses PrÉcurseurs FranÇais has been published, and gives a long list of definitions of the term "species" which from time to time have been enunciated by as many naturalists of the highest standing as such (pp. 186-187). But while none of these twenty or more definitions is logical in the sense just defined, they all present one or other of the differentiae given by those in the text.

[123] Darwinism, p. 167.

[124] Nature, Dec. 12, 1889, p. 129.

[125] Darwinism, p. 77.

[126] Darwinism, p. 77.

[127] Pascoe, The Darwinian Theory of the Origin of Species, 1891, pp. 31-33, and 46.

[128] Neuer Beitrag zum geologischen Beweis der Darwinischen Theorie, 1873.

[129] The Doctrine of Descent and Darwinism, Eng. Trans. p. 102.

[130] Origin of Species, p. 175.

[131] Ibid. p. 176: italics mine.

[132] Origin of Species, p. 122.

[133] A Manual of Dental Anatomy, p. 455.

[134] It may be observed that this distinction was not propounded by Mr. Wallace—nor, so far as I am aware, by anybody else—until he joined issue with me on the subject of specific characters. Whether he has always held this important distinction between specific and generic characters, I know not; but, as originally enunciated, his doctrine of utility as universal was subject to no such limitation: it was stated unconditionally, as applying to all taxonomic divisions indifferently. The words have already been quoted on page 180; and, if the reader will turn to them, he may further observe that, prior to our discussion, Mr. Wallace made no allowance for the principle of correlation, which, as we have seen, furnishes so convenient a loop-hole of escape in cases where even the argument from our ignorance of possible utility appears absurd. In his latest work, however, he is much less sweeping in his statements. He limits his doctrine to the case of "specific characters" alone, and even with regard to them makes unlimited drafts upon the principle of correlation.

[135] Darwinism, p. 297.

[136] Darwinism, pp. 292-3.

[137] Since the above was written both Mr. Gulick and Professor Lloyd Morgan have independently noticed the contradiction.

[138] Darwinism, p. 302.

[139] American Journal of Science, Vol. XL. art. I. on The Inconsistencies of Utilitarianism as the Exclusive Theory of Organic Evolution.

[140] Vol. xli. p. 438.

[141] Nature, vol. xli. p. 486.

[142] Ibid. vol. xlii. p. 52.

[143] Presidential Address to the Bristol Naturalists' Society, 1891.

[144] Presidential Address to the Bristol Naturalists' Society, 1891.

[145] A Theory of Heredity, Journal of Anthropological Institute, 1875. Vol. v. p. 345.

[146] No one has supposed that the tendency need be "strong": it has only to be persistent.

[147] Of course it must be observed that degeneration of complexity involves also degeneration of size, so that a more correct statement of the case would be—Why, under the cessation of selection, does an organ of extreme complexity degenerate much more rapidly than one of much less complexity? For example, under domestication the brains of rabbits and ducks appear to have been reduced in some cases by as much as 50 per cent. (Darwin, and Sir J. Crichton Browne.) But if it is possible to attribute this effect—or part of it—to an artificial selection of stupid animals, I give in the text an example occurring under nature. Many other cases, however, might be given to show the general rule, that under cessation of selection complexity of structure degenerates more rapidly—and also more thoroughly—than size of it. This, of course, is what Mr. Galton and I should expect, seeing that the more complex a structure the greater are the number of points for deterioration to invade when the structure is no longer "protected by selection." (On the other hand, of course, this fact is opposed to the view that degeneration of useless structures below the "birth-mean" of the first generations, is exclusively due to the reversal of selection; for economy of growth, deleterious effect of weight, and so forth, ought to affect size of structure much more than complexity of it.) But I choose the above case, partly because Professor Lloyd Morgan has himself alluded to "the eyes of crustacea," and partly because Professor Ray Lankester has maintained that the loss of these eyes in dark caves is due to the reversal of selection, as distinguished from the cessation of it. In view of the above parenthesis it will be seen that the point is not of much importance in the present connexion; but it appears to me that cessation of selection must here have had at least the larger share in the process of atrophy. For while the economy of nutrition ought to have removed the relatively large foot-stalks as rapidly as the eyes, I cannot see that there is any advantage, other than the economy of nutrition, to be gained by the rapid loss of hard-coated eyes, even though they have ceased to be of use.

[148] Since the above was written Professor Weismann has transferred this doctrine from the Protozoa to their ancestors.

[149] Darwinism, p. 131. He says:—"I have looked in vain in Mr. Darwin's works for any such acknowledgement" (i.e. "that a large proportion of specific distinctions must be conceded useless to the species presenting them").

[150] Origin of Species, p. 175. Italics mine.

[151] Darwinism, p. 132.

[152] Darwinism, p. 142.

[153] Life and Letters, vol. iii. p. 161.

[154] Life and Letters, vol. iii. p. 158.

[155] It must be observed that Darwin uses this word, not as Mr. Wallace always uses it (viz. as if correlation can only be with regard to adaptive characters), but in the wider sense that any change in one part of an organism—whether or not it happens to be an adaptive change—is apt to induce changes in other parts.

[156] Origin of Species, pp. 157-8.

[157] Ibid.

[158] Origin of Species, pp. 157-8.

[159] Descent of Man, p. 615.

[160] Ibid.

[161] Descent of Man, pp. 159-60.

[162] Descent of Man, p. 176.

[163] The passage to which these remarks apply is likewise quoted, in the same connexion as above, in my paper on Physiological Selection. In criticising that paper in Nature (vol. xxxix. p. 127), Mr. Thiselton Dyer says of my interpretation of this passage, "the obvious drift of this does not relate to specific differences, but to those which are characteristic of family." But in making this remark Mr. Dyer could not have read the passage with sufficient care to note the points which I have now explained.

[164] Origin of Species, p. 171.

[165] Ibid. p. 421.

[166] Origin of Species, pp. 372-373.

[167] Mr. Thiselton Dyer in Nature, loc. cit.

[168] Origin of Species, p. 171.

[169] Ibid. p. 175.

[170] Variation, &c., vol. ii. p. 260.

[171] Ibid. vol. ii. p. 261.

[172] Variation, &c., vol. ii. p. 280.

[173] Descent of Man, pp. 473-4.

Transcriber's Note

The following typographical errors were correctred.

Page	Error	Correction
10	dicussion	discussion
45	thoughout	throughout
229	pyschological	psychological

The following inconsistent hyphenations were changed.

Page	Original	Changed to
34	inter-crossing	intercrossing
46	re-appear	reappear
123	re-act	react
132	eye-lid	eyelid
216	lifetimes	life-times
217	lifetime	life-time
317	threefold	three-fold

The following inconsistent hyphenations were not changed.

"somatoplasm" (3 instances) and "somato-plasm" (2 instances)
"twofold" (2) and "two-fold" (1)
"interaction" (1) and "inter-action" (1)
"supernatural" (1) and "super-natural" (1)

Other changes:

Page 16 Footnote 10 - double quotes around "acceleration" and "retardation" changed to single quotes. A double quote inserted at the end.

In the Index - Entries "On Truth" and "Orang-utan, teeth of" moved from under "M" to under "O".

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