I quite accept the validity of your criticism of my physiological selection in your book, supposing your 'self-adaptation' true to the extent you suppose. But otherwise what you say tells in favour of physiological selection, at least, excepting the statement as to new allied species originating as a rule on distant areas from parent types. This, however, is certainly an erroneous statement, though I should like to know how you came to make it. I much wish I could write more or meet you. For, notwithstanding apparent bluntness (for brevity's sake), I see you are one of the few evolutionists who think for yourself. With many thanks, yours very truly, G. J. ROMANES. I am not against your criticism of natural selection, for I have always thought there must be some other additional principle of adaptation at work. Grand Hôtel, Costebelle, Hyères (Var): March 12. Dear Mr. Henslow,--My husband has much enjoyed your long and clear letter which I have just read to him. He is too ill to reply himself, but he will dictate a few notes to me to send to you. Yours very truly, ETHEL ROMANES. (A) I cry 'Peccavi' _as regards natural selection co-operating with self-adaptation_. Since you show that, even if it does, you are not concerned with this fact--_i.e._ of the _development of the adaptation_, but only with its origin. (B) All the same, however, we must remember that where high elaboration of mechanism is concerned, the question as to the _causes of its development_ become of more importance than those _of its origin_; _e.g._ even if self-adaptation be conceived capable of making a _first step_ towards producing the exquisite mechanism of a bivalve shell, by discriminate variation, _how is it conceivable_ that it should _go on_ through _the odd millions of successive steps_ of improvement needed to produce the perfect mechanism in which the great wonder of adaptation really occurs? I can conceive of _no natural process to accomplish this development_ even in one such case of mechanism _other than natural selection_. Let alone the 'endless variety' of elaborate mechanism elsewhere. (C) Of course, if you could _prove_ that indiscriminate variations have not occurred in wild plants, but only under cultivation, _you would destroy Darwinism_--_in toto_. But is the proposition credible _a priori_; or sustainable _a posteriori_, &c.? I suppose you have read Wallace on the subject as regards wild animals, and if you were to make similar _measurements_ with regard to _wild plants_, you would obtain analogous results. I remember as a boy having a game of who could find most specimens of fern-leaved clover in a given time, or even two leaves of clover which would be exactly alike in all respects. But I have already discussed the matter of definite and indefinite variability in 'Darwin and after Darwin.'