WCP6799

[1]

[illeg. printed address]

July 12/[18]90

Dear Mr. Gulick,

From your letter of the 5^th ult. just received, it would appear that we have at last discovered a point of disagreement. But as regards it I must hold to my ^deliberate opinion as expressed in Nature. Your thought has swept a much wider range than mine, and also gone much more into detail. In the categorical abstract of many beliefs[?] ^{statement of general conclusions} to which you refer, there was no room to quote from you; but in the lectures themselves I have endeavoured to do justice, as I hope you will see when they are published. [2]

It is a matter of interest as well as encouragement to me to find how closely parallel our minds continue to run. While your letter was on its way, I had been considering the very question of nomenclature with which it deals, and this [illeg.] exactly the same points of view.

In the lecture I explained that the term "Isolation" was extended in the way you notice, because several naturalists in their criticisms of our views (private as well as public) had so employed it, and seemed better to understand what is required the principle of segregation where when called by that name than when called by any other (e.g. F. Darwin, Lankester, Dyer, <Subokin?>. On the other hand, the term "Isolation" if thus extended, certainly does labour under [3] the objections which you now independently express. Under these circumstances I have more recently had recourse to the expedient of coining[?] a word, and in my article for the Nineteenth Century replying to Mr. Wallace, speak of the principle of Segregation, ^Isolation, Like to Like, Prevention of Free Intercrossing, or so forth as Homogamy. The derivation of this term will be immediately apparent to all biologists, and so serve to describe exactly what is meant by the pairing of like with like (or of individuals belonging to the same variety), to the exclusion of nonlike[?]. I think it is better than homoigamy (which would doubtless be more literally accurate as rendering the [4] idea of like mating with like), because, besides being less artificial[?] in appearance, both its constituent words are already current coin in biology.

Of course the use of this term would not exclude that of its (to us) equivalent, "Segregation". But the idea conveyed by segregation has nothing to do with breeding, and I believe that this is one reason why we are not better understood by naturalists: they do not in thought give the term the same specialized signification which we do; and even when you speak of "segregate breeding" I am concerned that not one reader in ten wants to understand ^{or to remember} your important distinction between it and "separate breeding". Therefore, if you approve of introducing homogamy as the equivalent of "segregate breeding", you might be more [5]¹ successful that than I have hither to been in finding a similarly <coined> term to serve as a brief and descriptive equivalent of "separate breeding", [—] "Amiscia" has the advantage of having been already coined by Weismann to signify separate breeding, though he includes under it also segregate breeding — he in fact never having distinguished between them² [—] then the term "Isolation" might be allowed to return to its original signification or the as employed by Darwin, Wagner[?], Weismann, etc., ^i.e. separate breeding due to geographical barriers.

Touching the term "Physiological Solution", as it has already gained so much currency, I fear, if it is changed, the idea will get about that my theory has changed also. I say, in this connexion[?], my theory [illeg.] we here touch upon the [6] only point with reference to which we ^do not completely agree. For while I draw a distinction between physiological incompatibility in its first stages ^or where it is concerned in the origin of species, you draw no distinctions between this stage and all other cases — [illeg.] where genera[?], etc. are concerned. In my lectures I give more fully than heretofore the grounds of my distinction, and reserve the term "Physiological Segregation" to include indiscriminately all cases of sexual incompatibility, whether as between varieties and species only ("physiological solution"), or likewise between genera, families, etc. The grounds of my distinction, briefly put, are these. In its first stages, where it is concerned in originating species in common areas, physiological incompatibility [7] may be properly designated the cause of divergence. But beyond these limits, such incompatibility becomes at most the negative condition to further divergence, while in the great majority of instances (if not actually in all instances above the limits of genera), it becomes only an accident[?] of divergence due to other causes. For example, no reasonable man will suppose that divergent evolution in mice is in any degree caused, influenced, or determined, by their sexual incompatibility with elephants, and, even within much nearer zoological affinities, the sexual incompatibility is clearly a subsequent result of the morphological differentiation: not the antecedent condition of ^to it. Therefore [8] what I call "physiological solution" is not concerned even in the origin of ^allied genera as it is in that of allied species. In the former case, and even where common areas[?] are concerned, the incompatibility is already given, and serves at most as a negative condition to further divergence due to other causes (of which physiological solution may continue to be one, in so far as the origination of new species is concerned). But in the latter case, the physiological incompatibility is the actual cause of the initial divergence, and then only it is that any selective process arises as due to such incompatibility. True, all subsequent divergence into genera, families etc., in the same line of descent, goes upon the negative condition of continued incompatibility; but now there is no longer any selective fertility in question: there is everywhere [9]³ absolute sterility already given as between these larger groups — sterility, therefore, which henceforth continues to be as much an accident of all further differentiation as if the groups concerned belonged to different sub-kingdoms. I should much like to know whether you follow my meaning in this, and, if so, whether you have any criticisms to offer.

On the whole, then, I propose for your consideration the following scheme, which I drew up 6 or 8 weeks ago.

Homogamy = Segregate Breeding

Amiscia = Separate Breeding

Independent Generations = other or both the above

Physiological Solution = Segregate fecundity, where segregate fecundity is concerned in the inception of varieties or species

Physiological Segregation = Segregate fecundity in general [10]

But if you could coin any good Greek term to signify separate breeding, Weismann's word Amiscia might be employed as the equivalent of our Independent Generation. There would then be three correlative words, all coined out of Greek, and severally serving to express the most important features of our system.

In alluding to my "General Conclusions", you speak of an "apparent contradiction involved in the statement that natural selection, though a 'kind of isolation', cannot of itself produce a 'case of isolation.'" But if you will refer to Props. 8 and 9 of the Conclusions, you will see that [11] what I deny to natural selection in the former to give rise to an "to create an additional case of isolation" — i.e. to give rise to more than a single case of isolation, unless it be assisted by some other kind of isolation. I deem this distinction between kinds and cases of isolation (or "homogamy") one of considerable importance for making matters clear to other minds — and, indeed, to keeping matters clear in one's own.

From the above scheme you will see that I have already employed the term "Physiological Segregation" in the sense which you propose, and desire to retain the term "Physiological Solution" in order to mark the particular case where such segregation is instrumental in the [12] origination of species — i.e. as I have always used this term, which, therefore, has never been co-extensive with your "segregate fecundity". Touching what you now say about the desirability[?] of restricting your term "fecundity" to the "abundant production of male and female elements", as distinguished from "affinity" between them ("fertility") , I think if you find any need to distinguish between these two things, "fecundity" and "fertility" are the best terms you could employ for the purpose. And I like "elemental" better than "physiological" in association with "co-variations[?]" and "<domination?>"; but am disposed to think that "sexual[?]" would be better than either.

I have just returned proof of your last paper to the Linnean Society. It is a master-piece of logical method, as of biological thought. No other essay in Darwinian literature appears to me so admirable. But we shall both be in our graves before it is generally appreciated; while the reckless and comparatively superficial Weismann will continue for some years to occupy the minds of evolutionists.

G. J. Romanes [signature]