My dear Sir

I have been unwell, so have delayed thanking you for your admirable letter.² I hope you will not think me presumptuous in saying how much I have been struck with your varied knowledge, & with the decisive manner in which you bring it to bear on each point,—a rare & most high quality, as far as my experience goes.— I earnestly hope you will find time to publish largely: before the Linn. Soc. you might bring boldly out your views on Species.— Have you ever thought of publishing your travels & working in them the less abstruse parts of your Nat. History? I believe it would sell, & be a very valuable contribution to Nat. History.—³ You must, also, have seen a good deal of the natives.

I know well it would be quite unreasonable to ask for any further information from you; but I will just mention that I am now & shall be for a long time writing on Domestic variation of all animals. Any facts would be useful; especially any showing that savages take any care in breeding their animals; or in rejecting the bad & preserving the good—or any fancies which they may have that one coloured or marked dog &c is better than another.— I have already collected much on this head, but am greedy for facts.— You will at once see their bearing on Variation under Domestication.

Your observations on Carabus, with respect to Glacial period, seem very important.—⁴ I daresay you know that some geologists have speculated on a Permian & even on a Challk Glacial period.— When considering plants of Australia, a suspicion crossed me that there must have been an ancient migration from N. temperate to S. temperate regions.— I feel sure that if you saw lists of plants in T. del Fuego—on isolated mountains of India, Java, Borneo, Abyssinia, S.E. Australia, Fernando Po, you would see that there must have been a very recent migration. This view is largely supported by plain geological facts.— I have a rather long M.S. discussion, well copied out, which Hooker has read, & which if you thought it worth your while, you might with welcome read;⁵ but I doubt whether it would be worth your while.— Hereafter when I come to Geograph. Distrib. (& God knows when that will be) I will deeply consider all your most valuable remarks.—⁶

Thank you for facts on intermediate vars. in intermediate regions; I can see how complex the case is; & I hope before I come to that subject you will have largely published. But the case you give is excellent.—

Hardly anything in your letter has pleased me more than about sexual selection. In my large M.S (& indeed in Origin with respect to tuft of hairs—on breast of Cock-Turkey)⁷ I have guarded myself against going too far; but I did not at all know that male & female butterflies haunted rather different sites. If I had to cut up myself in a Review, I would have worked & quizzed Sexual selection; therefore, though I am fully convinced that it is largely true, you may imagine how pleased I am at what you say on your belief.— This part of your letter to me is a quintessence of richness.— The fact about Butterflies attracted by coloured sepals is another good fact, worth its weight in Gold.⁸ It would have delighted the heart of old Christian C. Sprengel,—now many years in his grave.—⁹

I am glad to hear that you have specially attended to “mimetic” analogies—a most curious subject.— I hope you will publish on it.¹⁰ I have for a long time wished to know whether what D^r. Collingwood asserts, is true, that the most striking cases generally occur between insects inhabiting the same country.—¹¹

Believe me | Yours most truly obliged | Ch. Darwin