I have been very frank, because I know you, and therefore that this is what you would prefer. But I am too ill to make myself clear in a letter. I wish you could stop here for a day on your way home, by which time I shall probably have read your books, and we might discuss the whole business before I publish mine on the Post-Darwinian Theories. With very many thanks, I remain yours very truly, G. J. ROMANES. Hôtel Costebelle, Hyères: February 24, 1894. Dear Mr. Henslow,--Nothing can be more clear than are all your letters, and the last one, I take it, sets at rest the only question which I had to ask. For it expressly answers that, in your own view, hypothesis of 'self-adaptation' is a _statement_ rather than an _explanation_ of the facts. Nevertheless, it is also to some certain extent advanced as an explanation on Lamarckian lines, for in your books (for which I much thank you) you attribute adaptive mechanism in flowers to thrusts, strains &c. caused by insects. But here, if I may say so, it does not seem to me that you sufficiently deal with an obvious criticism, viz. How is it so much as conceivable that protoplasm should always respond to insect irritation adaptively, when we look to the endless variety and often great elaboration of the mechanism? Similarly as regards the inorganic environment, Lamarck's hypothesis of _use_-inheritance (_i.e._ mere increase and decrease of parts as due to inherited efforts of greater or less development by altered flow of nutrition) was at least theoretically valid. But how can you extend this to structures which, though _useful_, are never _active_, so as to modify flow of nutrition, _e.g._ hard shells of nuts, soft pulp of fruits, &c.? Here it is that natural selection theory has the pull. And so of adaptive _colours_, _odours_, and _secretions_? I confess that, even accepting inheritance of acquired characters, I could conceive of 'self-adaptation' alone producing all such innumerable and diversified adjustments only by seeing with Newman (in his 'Apologia') an angel in every flower. Besides, I do not see why you are shut up to this, even on your own principles. For surely, be there as much self-adaptation in Nature as ever you please, it would still be those individuals (or _incipient types_) _which best respond_ to stimulation (_i.e._ most adaptively do so) that, other things equal, would survive in the struggle for existence, and so be naturally selected. In other words, I do not see why you should accept natural selection as regards 'vigour' of seedlings, and nowhere else.