My dear Sir

I want to beg one more favour to the many which formerly you have conferred on me.² I am extremely much interested in regard to the blind cave animals, described some time since in your Journal by Prof. Silliman Jun^r.,³ as the subject is connected with a work of somewhat general nature, which I am endeavouring to draw up on variation & the origin of species, classification &c.—

Are the specimens at Newhaven? and if so could you get any good entomologist to look at the insects— What I want to know is, whether any of the Crustacea, spiders, insects (flies beetles, crickets &c) & Fish belong to the American type⁴ (Has not Agassiz noticed the Fish?)⁵ ie to genera or sections of genera, found only on the American continent.— I sh^d. be most grateful for any, the least, information on this head.— All the American mice have a peculiar character in their teeth by which they can be recognised.—

Secondly I have been rereading with renewed interest your memoir on geograph. Distrib. of Crustacea⁶ & I want to ask a question on this head: Botanists have remarked on several cases in which northern temperate & arctic genera have sent the same or representative species into corresponding zones of S. hemisphere.— You give several similar & striking cases; but I do not feel sure from my ignorance that these genera can be called from their general affinities & range strictly northern genera. How is this? Might they not be called southern genera, which have sent species to the North: I ask this because in plants, it is very remarkable as observed by D^r. Hooker & A. Decandolle, that southern genera have not their represetatives or identical species in the north, though there are so many cases of northern genera which have their congeners & same individual species in the south.— Will you be so very kind as to reflect on this, & take the trouble to inform me.⁷

Lastly can you remember whether any author (I think M^r Eights whose writings I have never seen) has described fossil trees in the S. Shetland islands.—⁸

Now I am sure I have put your kindness to a severe proof, & can only beg to be forgiven.— If you have a few minutes to spare, I sh^d. very much like to hear a little news of yourself, & whether all things go well with you. Are you at work at any particular great subject? I should expect so, though no one whatever in the world has a better right to rest on his oars than you have. I never cease being fairly astounded at the amount of labour which you have performed.— But the other day I was sitting at dinner by Prof. Miller of (our) Cambridge,⁹ & he was speaking warmly on your mineralogical work.—

As for myself I live a very quiet & retired life, with a large set of very happy & good children round me, & do daily 3 or 4 hours work at Natural History; for more than which I have not, & shall never have, strength.— Our neighbour J. Lubbock, has married a young & pretty wife, & a very young couple they are reckoned in this country, & I think & hope he will be as happy as he deserves: he works away during the very little leisure which he has, at his Entomostraca, & if he could give himself up to Nat. History, he would make a capital Naturalist.¹⁰

Pray believe me, my dear Sir, with every good wish & sincere respect. | Yours very truly | Ch. Darwin

I have directed this to care of Prof. Silliman; as I heard some time since that you were Professor of Geology at some new place.¹¹