Dear Sir

I thank you sincerely for your letter which has interested & gratified me extremely.² If you had had leisure or inclination to have made any general criticisms on the “Origin of Species”; they would have been very far from “superfluous”; for I know hardly anyone whose opinions I should be more inclined to defer to.— I will trouble you with a few remarks on some parts of your letter.

Few facts have interested me more than your case of the black Hogs; it shows such a marvellous relation of mere colour, (generally thought to be so unimportant) & constitution: I have long suspected that such correlation of colour & tendency to fevers, might possibly explain the origin of colour of negros; but I can get no facts to support this crude speculation.³ I have been the more glad to get your Hog case, as I was hardly able to credit the parallel case of sheep in Sicily.⁴

With respect to the Cave Rat; I knew that it was a strictly American form;⁵ but I did not at all know that the genus had large eyes.—   I know how busy you are, & that you do not much like writing letters; but if you could get me a little information about this Rat, it would be a great kindness.— Firstly, are the eyes of the Cave species not at all larger than in the other species? Secondly, may I trust Prof. Silliman, that the Rat was blind & when kept out of cave, it seemed to acquire some power of vision?⁶ And lastly does it inhabit the profoundest depths of caves, or less profound parts?—

As I am asking questions, I will ask one other; viz were you struck with any peculiarity in length of hind(?) legs (I am writing away from home, & cannot consult my notes) of the Nãta Cattle? I procured a skull; but it has never been described:⁷ would it not be worth your while to insert in some Journal a short description together with the parallel case of the Cod Fish? If you do will you inform me.—⁸ From various sources of information I cannot doubt that the breed is rather ancient, & extremely true: I have copious notes on subject, which I hope some day to use.—

Speaking of inheritance, I was long inclined to entirely disbelieve with you, that Mutilations are ever inherited; (& I got special enquiries made about the Jews); but I have of late been rather staggered; & now Brown-Sequard’s case of inherited epilepsy from mutilation seems to almost settle question.⁹ I have suspected from some facts that mutilations are inherited only when they produced disease. A clever young Surgeon carefully dissected the eyes of the Tucutucu, which I brought home in Spirits, & assured me that there were traces of inflammation.¹⁰ My Spanish informant had no motive, (for I asked no question) to tell me falsely how often they were blind. Does not the case of Cats with blue eyes being deaf (when one blue eye deaf on one side alone of head) strike you as a very odd case: I have lately observed that all kittens have blue eyes when they first open them; & before they open them, they seem to me after several trials, absolutely deaf;—so that I fancy there is at first some correlation between the blue eyes & deafness, & that the blueness is carried on in the old cats, by a sort of correlation or arrest of development the deafness continues; but my ideas are vague enough.—¹¹

With respect to spinal stripe of Horse; I think it is much too common (& characteristic of every species of the genus) to be explained as your American informant supposes: the stripe seems to be commonest with with colts than with old Horses; in same manner as the foals of the E. Hemionus are well striped when first born.—

I have been very glad to hear your remarks on the Brain of Chimpanzee; as will Sir C. Lyell be.—¹² D^r. Falconer tells me that Huxley gave Owen the most severe setting down at Oxford on this subject, that ever man received.—¹³ I fear the general opinion is true, that Owen truckles to the approbation of those high in church & state. I declare I believe, from some conversation with him that at the bottom of his heart he goes a long way with me on the origin of species, though he has attacked me so severely & not very ingenuously in the Edinburgh Review.—¹⁴ No one other person understands me so thoroughly as Asa Gray. If ever I doubt what I mean myself, I think I shall ask him! His generosity in getting my views a fair hearing, & not caring himself for unpopularity has been most unselfish,—I would say noble.

Forgive me for writing at such length & believe me Dear Sir, with cordial thanks & sincere respect. | Yours very faithfully | C. Darwin