You will, I think, be glad to hear that I now often hear of naturalists accepting my views more or less fully; but some are curiously cautious in running the risk of any small odium in expressing their belief.
LETTER 123. TO H.W. BATES. Down, April 4th [1861].
I have been unwell, so have delayed thanking you for your admirable letter. I hope you will not think me presumptuous in saying how much I have been struck with your varied knowledge, and with the decisive manner in which you bring it to bear on each point,--a rare and most high quality, as far as my experience goes. I earnestly hope you will find time to publish largely: before the Linnean Society you might bring boldly out your views on species. Have you ever thought of publishing your travels, and working in them the less abstruse parts of your Natural History? I believe it would sell, and be a very valuable contribution to Natural History. 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, and shall be for a long time, writing on domestic varieties 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 and preserving the good; or any fancies which they may have that one coloured or marked dog, etc., 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.
Hardly anything in your letter has pleased me more than about sexual selection. In my larger MS. (and indeed in the "Origin" with respect to the tuft of hairs on the breast of the cock-turkey) I have guarded myself against going too far; but I did not at all know that male and female butterflies haunted rather different sites. If I had to cut up myself in a review I would have [worried?] and 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. It would have delighted the heart of old Christian C. Sprengel--now many years in his grave.
I am glad to hear that you have specially attended to "mimetic" analogies-- a most curious subject; I hope you publish on it. I have for a long time wished to know whether what Dr. Collingwood asserts is true--that the most striking cases generally occur between insects inhabiting the same country.
LETTER 124. TO F.W. HUTTON. Down, April 20th [1861].
I hope that you will permit me to thank you for sending me a copy of your paper in "The Geologist" (124/1. In a letter to Hooker (April 23rd?, 1861) Darwin refers to Hutton's review as "very original," and adds that Hutton is "one of the very few who see that the change of species cannot be directly proved..." ("Life and Letters," II., page 362). The review appeared in "The Geologist" (afterwards known as "The Geological Magazine") for 1861, pages 132-6 and 183-8. A letter on "Difficulties of Darwinism" is published in the same volume of "The Geologist," page 286.), and at the same time to express my opinion that you have done the subject a real service by the highly original, striking, and condensed manner with which you have put the case. I am actually weary of telling people that I do not pretend to adduce direct evidence of one species changing into another, but that I believe that this view in the main is correct, because so many phenomena can be thus grouped together and explained. But it is generally of no use; I cannot make persons see this. I generally throw in their teeth the universally admitted theory of the undulation of light,--neither the undulation nor the very existence of ether being proved, yet admitted because the view explains so much. You are one of the very few who have seen this, and have now put it most forcibly and clearly.