We now pass on to our consideration of Darwin's opinion touching the question, as stated by himself,—"The doctrine of utility, how far true?" As I cannot ascertain that Darwin has anywhere expressed an opinion as to whether natural selection has been necessarily concerned in the origin of all species, the issue here is as to whether he held this with regard to all specific characters. It will be remembered that while opposing this doctrine as erroneous both in logic and in fact, I have represented that it is not a doctrine which Darwin sanctioned; but, on the contrary, that it is one which he expressly failed to sanction, by recognizing the frequent inutility of specific characters. Mr. Wallace, on the other hand, alleges that Darwin did believe in the universal—as distinguished from the general—utility of such characters. And he adds that he has "looked in vain in Mr. Darwin's works" for any justification of my statements to the contrary[149]. Therefore I will endeavour to show that Mr. Wallace's search has not been a very careful one.
We must remember, however, that it was not until the appearance of my paper on Physiological Selection, four years after Darwin's death, that the question now in debate was raised. Consequently, he never had occasion to deal expressly with this particular question—viz. whether "the doctrine of utility" has any peculiar reference to specific characters—as he surely would have done had he entertained the important distinction between specific and all other characters which Mr. Wallace now alleges that he did entertain. But, be this as it may, we cannot expect to find in Darwin's writings any express allusion to a question which had not been raised until 1886. The most we can expect to find are scattered sentences which prove that the distinction in question was never so much as present to his mind,—i. e. never occurred to him as even a possible distinction.
I will first take the passages which Mr. Wallace himself supplies from among those which I had previously indicated.
"But when, from the nature of the organism and of the conditions, modifications have been induced which are unimportant for the welfare of the species, they may be, and apparently often have been, transmitted in nearly the same state to numerous, otherwise modified, descendants[150]."
On this passage Mr. Wallace remarks that the last five words "clearly show that such characters are usually not 'specific,' in the sense that they are such as distinguish species from one another, but are found in numerous allied species." But I cannot see that the passage shows anything of the sort. What to my mind it does show is, (a) that Mr. Darwin repudiated Mr. Wallace's doctrine touching the necessary utility of all specific characters: (b) that he takes for granted the contrary doctrine touching the inutility of some specific characters: (c) that without in this place alluding to the proportional number of useless specific characters, he refers their origin in some cases to "the nature of the organism" (i.e. "spontaneous variability" due to internal causes), and in other cases to "the conditions" (i.e. variability induced by external causes): (d) that when established as a specific character by heredity, such a useless character was held by him not to tend to become obsolete by the influence of natural selection or any other cause; but, on the contrary, to be "transmitted in nearly the same state to numerous, otherwise modified, descendants"—or progeny of the species in genera, families, &c.: (e) and, therefore, that useless characters which are now distinctive of genera, families, &c., were held by him frequently, if not usually, to point to uselessness of origin, when first they arose as merely specific characters. Even the meaning which Mr. Wallace reads into this passage must imply every one of these points; and therefore I do not see that he gains much by apparently seeking to add this further meaning—viz. that in Darwin's opinion there must have been some unassignable reason preventing the occurrence of useless specific characters in cases where species are not destined to become the parents of genera.
Moreover, any such meaning is out of accordance with the context from which the passage is taken. For, after a long consideration of the question of utility, Darwin sums up,—"We thus see that with plants many morphological changes may be attributed to the laws of growth and the interaction of parts, independently of natural selection." And then he adds,—"From the fact of the above characters being unimportant for the welfare of the species, any slight variations which occurred in them would not have been augmented through natural selection." Again, still within the same passage, he says, while alluding to the causes other than natural selection which lead to changes of specific characters,—"If the unknown cause were to act almost uniformly for a length of time, we may infer that the result would be almost uniform; and in this case all the individuals of the species would be modified in the same manner." For my own part I do not understand how Mr. Wallace can have overlooked these various references to species, all of which occur on the very page from which he is quoting. The whole argument is to show that "many morphological changes may be attributed to the laws of growth and the inter-action of parts [plus external conditions of life], independently of natural selection"; that such non-adaptive changes, when they occur as "specific characters," may, if the species should afterwards give rise to genera, families, &c., become distinctive of these higher divisions. But there is nothing here, or in any other part of Darwin's writings, to countenance the inconsistent notion which Mr. Wallace appears to entertain,—viz. that species which present useless characters are more apt to give rise to genera, families, &c., than are species which do not present such characters.
The next passage which Mr. Wallace quotes, with his comments thereon, is as follows. The italics are his.
"'Thus a large yet undefined extension may safely be given to the direct and indirect results of natural selection; but I now admit, after reading the essay of Nägeli on plants, and the remarks by various authors with respect to animals, more especially those recently made by Professor Broca, that in the earlier editions of my Origin of Species I perhaps attributed too much to the action of natural selection, or the survival of the fittest. I have altered the fifth edition of the Origin so as to confine my remarks to adaptive changes of structure; but I am convinced, from the light gained during even the last few years, that very many structures which now appear to be useless, will hereafter be proved to be useful, and will therefore come within the range of natural selection. Nevertheless I did not formerly consider sufficiently the existence of structures which, as far as we can at present judge, are neither beneficial nor injurious; and this I believe to be one of the greatest oversights as yet detected in my work.'
Now it is to be remarked that neither in these passages nor in any of the other less distinct expressions of opinion on this question, does Darwin ever admit that "specific characters"—that is, the particular characters which serve to distinguish one species from another—are ever useless, much less that "a large proportion of them" are so, as Mr. Romanes makes him "freely acknowledge." On the other hand, in the passage which I have italicised he strongly expresses his view that much of what we suppose to be useless is due to our ignorance; and as I hold myself that, as regards many of the supposed useless characters, this is the true explanation, it may be well to give a brief sketch of the progress of knowledge in transferring characters from the one category to the other[151]."