WCP6798

[1]

Feb.15/[18]90

Dear M^r. Gulick,

In accordance with you first letter, I sent your longer MS reply to M^r Wallace to the Sec. of the Linnaean Society; and now, in accordance with your second letter, forward your shorter reply to the the Editor of Nature.

I have quoted extensively from the longer one in Notes to a course of lectures which I am preparing for publication. I suppose you have no objection to this — the quotations being all in inverted commas.

It appears to me desirable that, as you and I are the only two human beings that who recognize the [2] full importance of "segregation" in all its forms, we should submit to each their own views before publication, in order that we may speak, as far as possible, with a common voice. Especially I think this is desirable in relation to Wallace's criticism; and therefore I will send you the main heads of my answers.

In your answer you show, I think conclusively, that what he calls "natural selection" on p 173 et seq., is not natural selection at all. To this I add that his whole criticism as against me ("physiological selection", p. 180 et seq.) goes upon the supposition that "segregate fecundity", if it can act at all, must necessarily act alone. Now, you have expressly argued that it always acts in association [3] with some other form of segregate branching ("negative" plus "positive"), while I have said I believe that it often does. Here then is what as far as I can see constitutes the one and only point of difference between you views and mine — viz., that you think segregate fecundity can never act alone, while I think that in some cases it may — particularly in plants and in animals which do not unite for each birth. But, disregarding this comparatively small point of difference between us, does it not seem to you that Wallace's criticism is in large part irrelevant as regards me, and wholly irrelevant as regards you? [4] In other words, his own theory, which he presents as original (pp 171-179) appear to me absolutely identical with yours, and almost absolute appears to me almost identical with mine, and absolutely identical with yours — so far, I mean, as his theory goes. It differs from yours only in not recognizing so many forms of segregate branching with which segregate fecundity may be involved (he recognizes only natural selection, sexual selection, or psychological preference, and occupation of different "stations"). But he is as emphatic as you and I are in recognizing the importance of segregate fertility as a factor in segregate branching; and his presentation [5]¹ of the matter differs from ours only in laying exclusive stress upon the infertility of second mongrels[?] as distinguished from first crosses. But your segregate fecundity and my physiological solution are in no way concerned to deny that the segregating process will be assisted in all cases where infertility extends from first crosses, so as also to include second. (Indeed, in writing my paper I took so obvious a point for granted). On the other hand, Wallace is demonstrably wrong when he in representing, that "it is this inferiority of the hybrid offspring that is the essential point". [6] The inferiority (infertility or otherwise) of the hybrid offspring cannot possibly re-act upon the sexual system of the parent forms, so as to induce segregate fecundity between them (sterility of mules cannot tend to induce sterility between horses and asses); and, therefore, the most that sterility of second crosses can do is to give infertility of first crosses the best chance of further development by preventing continual dilution ^through intercrossing of the hybrids with one another ^{(thus multiplying their numbers)} and with the parent forms. In other words, sterility of second crosses acts as a <favouring> negative condition to the operation of whatever positive causes are at work upon the sexual systems of the parent forms, and which are leading to infertility of first crosses. Moreover, [7] even this negative condition, when present, is itself ultimately due to change taking place in the sexual systems of the parent forms, and is therefore itself a cause or [illeg.] of "segregate fecundity", But, observe, if this is the only [illeg.] of segregate fecundity that has arisen, it can never of itself lead to a differentiation of specific type. It may materially help the differentiation when infertility arises between first crosses; but this is all that it can do, even if assisted by "natural selection" in the way that Wallace supposes. Indeed, he himself seems to have had a glimmering ^perception of this fact; for in the middle of p. 175 he quietly slips in as given the occurrence of segregate fecundity between the [8] first crosses — due to unknown causes acting on the sexual systems of the parent forms, or causes quite other than the negative conditions of sterility between the second crosses, which, nevertheless, he immediately proceeds to declare "the essential point".

On the whole, then, I hope in your future answers you will go with me in pointing out that Wallace has really adopted the theory of physiological solution, or segregate fecundity, in toto, ^and while professing to reject it, gives it forth in a more less inaccurate form as original.

If the above is not fully intelligible, I will, should you so desire, send you a copy of my MSS on these points

Yours very truly, | Geo. J. Romanes [signature]