[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.