My dear Sir

I thank you warmly for your letter,² which like every one received from you, was most kind & interesting.— Your information on the points, on which I asked, is much fuller than I anticipated; I am glad to find that I deduced nearly or quite accurate results from your work with respect to the Crustacea,³ but I am always afraid of falling into error when coming to conclusions on subjects on which I am almost ignorant. Very many thanks, also, for facts about the Caves, which to me is a wonderfully interesting subject: one point I forgot & if there be a specimen of the Cave Rat at New Haven & if you have anyone there au fait at Rodents, I sh^d. very much wish to know whether its teeth are on the New or Old world type as pointed out by Waterhouse in regard to the great genus Mus.⁴ But you must not take much trouble on this head, as I have too often given you trouble, & I look at your time as very precious.—

I shall be very curious to see your Embryogeny of N. America!⁵ What a striking case of vertebræ in tail of young Gar-Pike; I wish with all my heart that Agassiz would publish in detail on his theory of parallelism of geological & embryological development;⁶ I wish to believe, but have not seen nearly enough as yet to make me a disciple.

I am working very hard at my subject of the variation & origin of species, & am getting M.S. ready for press, but when I shall publish, Heaven only knows, not I fear for a couple of years but whenever I do the first copy shall be sent to you.— I have now been for 19 years with this subject before me; but it is too great for me, especially as my memory is not good. I have of late been chiefly at work on domestic animals, & have now got a considerable collection of skeletons: I am surprised how little this subject has been attended to: I find very grave differences in the skeletons for instance of domestic rabbits, which I think have all certainly descended from one parent wild stock. But Pigeons offer the most wonderful case of variation, & as it seems to me conclusive evidence can be offered that they are all descended from C. livia.

In the case of Pigeons, we have (& in no other case) we have much old literature & the changes in the varieties can be traced. I have now a grand collection of living & dead Pigeons; & I am hand & glove with all sorts of Fanciers, Spital-field weavers & all sorts of odd specimens of the Human species, who fancy Pigeons.—

I know that you are not a believer in the doctrine of single points of creation, in which doctrine I am strongly inclined to believe, from general arguments; but when one goes into detail there are certainly frightful difficulties.⁷ No facts seem to me so difficult as those connected with the dispersal of Land Mollusca.⁸ If you ever think of, or hear of, any odd means of dispersal of any organisms I sh^d. be infinitely obliged for any information; as no one subject gives me such trouble as to account for the presence of the same species of terrestrial productions on oceanic islands; for I cannot swallow the prevalent fashion in England of believing that all islands within recent times have been connected with some continent.—

You will be rather indignant at hearing that I am becoming, indeed I sh^d. say have become, sceptical on the permanent immutability of species: I groan when I make such a confession, for I shall have little sympathy from those, whose sympathy I alone value.— But anyhow I feel sure that you will give me credit for not having come to so heterodox a conclusion, without much deliberation. How (I think) species become changed I shall explain in my Book, but my views are very different from those of that clever but shallow book, the Vestiges.—⁹

It is my intention to give fully all the facts in favour of the eternal immutability of species & I have taken as much pains to collect them, as I possibly could do. But what my work will turn out, I know not; but I do know that I have worked hard & honestly at my subject.

Agassiz, if he ever honours me by reading my work, will throw a boulder at me, & many others will pelt me; but magna est veritas &c, & those who write against the truth often, I think, do as much service as those who have divined the truth; so that if I am wrong I must comfort myself with this reflection. It may sound presumptious, but I think I have to a certain extent staggered even Lyell.—¹⁰

But I am scribbling (in a very bad handwriting moreover) in a shameful manner all about myself; so I will stop with cordial good wishes for yourself & family, & pray believe me, my dear Sir | Your sincere & heteredox friend | Ch. Darwin

We are all here now much interested in American politics—¹¹ You will think us very impertinent, when I say how fervently we wish you in the North to be free.—

P.S. | I have long thought that geologists not having found this or that form in this or that formation was very poor evidence of such forms not having then existed; in this respect differing, as wide as the poles, from the great Agassiz, who seems to me to retreat a step & take up a new position with a front so bold as to be admirable in a soldier.— Well, in case of cirripedes I thought, as stated in Preface in my Fossil Lepadidæ, that the evidence was so good, that I did believe that no Sessile cirripede existed before the Tertiary period. But yesterday I received from M. Bosquet of Maestricht a beautiful drawing of perfect Chthamalus from the Chalk!!—¹²

Never again will I put any trust in negative geological evidence.—