And now for your last letter. Read in the light of subsequent experience, I have no doubt that I ought to have expressed myself with more care while writing my paper. But, to tell the honest truth, it never once occurred to me that I of all men could be suspected of trying to undermine the theories of Darwin. I was entirely filled with the one idea of presenting what seemed to me 'a supplementary hypothesis,' which, while 'in no way opposed to natural selection,' would 'release the latter from the only difficulties' which to my mind it had ever presented. Therefore I took it for granted that everybody would go with me in recognising natural selection as the 'boss' round which every 'other theory' must revolve, without my having to say so on every page. So, of course, by 'other theory' I did not mean that physiological selection was in my opinion the only theory of the origin of species. Everywhere throughout the paper, from the title-page to the conclusion, I represented it as an 'additional suggestion,' a 'supplementary hypothesis,' &c., &c. Sexual selection is in my view (as it is also in Darwin's, Wallace's, and doubtless that of all evolutionists) one of the 'other theories that have been propounded on the origin of species.' So is Lamarck's theory, which was considered by Darwin as more or less 'supplementary' to natural selection; and this is all that I meant—or, I should say, could possibly be understood to mean in view of the title-page, &c.—by speaking of physiological selection as another theory of the origin of species. It certainly is not the same thing as natural selection or either of the 'other theories' just mentioned; but no less certainly it is not exclusive of any of the three. Unquestionably it is as you say, and as I myself said, an independent theory—i.e. not identical with, but additional to, that of natural selection. But this is a widely different thing from saying that it is in itself an exhaustive theory, which must therefore swallow up all or any 'others.' In short, I abide by the closing statement of my introductory paragraph—viz. that the theory is an 'attempt at suggesting another factor in the formation of species, which, although quite independent of natural selection, is in no way opposed to natural selection, and may therefore be regarded as a factor supplementary to natural selection.' Statements to the same effect are indeed scattered through the entire paper; but, of course, could I have foreseen the interpretations which afterwards arose, I should have reiterated such statements ad nauseam.
Sorry you cannot come to the B.A., or to dine, but certainly do not wonder.
Yours very sincerely,
G. J. Romanes.
Lastly, about species not being able to exist as species without the physiological isolation of physiological selection (p. 403), the statement of course only applies to nearly allied species occupying common areas (see p. 404). If this statement is wrong, no one has yet shown me wherein it is so. I fancy you do not quite appreciate that by 'sterility' I always mean (unless otherwise expressly stated) sterility in some degree, and this not only with regard to the fertile hybrids. It is by no means enough to point to natural and fertile hybrids as cases opposed to physiological selection unless it has been shown by experiment through a generation or two that these hybrids are fully fertile—i.e. as fertile as their parent species. Now, experiments of this kind have rarely been carried through. If you assume that the result of carrying them through would be destructive of physiological selection by proving that fertile hybrids are, as a rule, fully fertile, and also (which is very important) that in any cases where experiment may show them to be so, further experiment would fail to show that isolation has not been effected in any other way (as by pre-potency, differences of insect fertilisation, &c.)—in short, if you assume that fertility is as complete between the two associated species as it is within each species, how is it conceivable that they should continue to be distinct? In this connection it is well to consult Gulick's paper already referred to (especially p. 259, paragraph 1st) on the theoretical side, and Jordan's papers and books on the practical side. I have repeated the latter's observations on poppies, and find that where any considerable number of individuals are concerned, natural selection is not nearly so great a power in this respect. (Even in cases where it happens that in-breeding is necessarily confined to single hermaphrodite individuals for numberless generations, the handicapping is not fatal: witness flowers which habitually fertilise themselves before opening—especially some species of orchids, which never seem to do otherwise, notwithstanding the elaborate provisions for cross-fertilisation in other species.) Now, I believe most of all in what I have called 'collective variation' of the reproductive system in the way of physiological selection, whereby, owing to some common influence acting on a large number of individuals similarly and simultaneously, they all become sexually co-adapted inter se while physiologically isolated from the rest. This essential feature of the theory seems to me entirely to remove the difficulty about in-breeding, as well as that which Wallace urged about the chances against a suitable meeting of 'physiological complements.'
As for my having attributed too much to the swamping effects of intercrossing (Panmixia), this, I am convinced, is the one and only particular wherein I have at all departed from the judgments of Darwin; though, curiously enough, it is the particular on which my critics have laid least stress when accusing me of Darwinian heresy. But it is too big a question to treat in correspondence. Gulick's recently published paper at the Linnean Society seems to me a most important one in this connection, and I have a large body of other evidence.
To F. Darwin, Esq.[64]
18 Cornwall Terrace, Regent's Park, N.W., January 8, 1889.
Dear Darwin,—Hate you, indeed! Why, I cannot imagine any better service than that of stopping a fellow from making a fool of himself, and I most cordially thank you for having done so in this case. The business was so completely out of my line, that I did not know what was required. It seemed to me that if I got any evidence of bending towards the sparks, the only question I wanted to answer would be answered, and, therefore, that it did not matter a straw about temperature, moisture, and the rest. Moreover, the results did not seem to me to be of any importance, as they were just what might have been expected, and, therefore, I doubted whether it was worth while publishing a paper about them. Had they gone, the other way, and proved that the plants would not bend to flashing light, I should have thought it much more interesting. Lastly, the research was so expensive, costing £1 per day at the only place where I could get the requisite apparatus, and there they shut up at night.
Of course, I will withdraw this paper, and, if you think the thing is worth working out in all the details you suggest, will do so. In that case, it would be worth while to ascertain whether there would be any electrical apparatus at Cambridge which I could get the use of at a lower rate of profit to the owners. A good-sized induction coil is really all that is required, and they probably have this in the Cavendish. But there is not one available in any of the London workshops, and so I had to go to Appes, in the Strand. It is suggested that the debate in Section D at the British Association this year should be opened by me on the question of utility as universal. Before I agree, I should like to know what you think about the 'Nature' controversy which I have recently had with Dyer, and out of which the present suggestion has emanated. Perhaps we might arrange to meet somewhere soon to have a talk over the expediency of such a debate at all, and the lines on which, if held, it should run. Of course, physiological selection would be carefully kept out. My object would be to show the prime importance of natural selection as a theory which everywhere accounts for adaptations.