[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.