My dear Sir,

When I had come home from Switzerland I heard from the publisher that your Essay on Expression would come out soon. The Athenaeum, he said, had given a notice of it.¹ At the same time he asked me to write to you, to inquire if you had already disposed of it. He should like very much to publish a translation and I should be most happy if you would allow me to translate it.² Pray be so kind as to let me know what your intentions are.

You asked me in one of your last letters how many copies of the Descent of Man had be sold in Germany.³ At the first an edition of 2000 copies was printed; that was sold very soon so that Mr Koch was obliged to make a reprint of 1000 copies. These again are nearly all sold; and now a second edition is printing. For that I revise the sheets with a copy of the Seventh thousand of the Original, which you kindly sent me through Mr Murray.⁴ Have you any thing to alter or are there still more recent additions? With respect of Vol. II. p 305 regarding the colour and stripes of horses you will be pleased I think to get the following quotation from Albertus Magnus (13^th. century). There I found (Opera, ed. Jammy Tom. VI. p 587) the following words: “Color autem naturalis equi qui in sylvestribus deprehenditur est cinereus per dorsum linea fusca a capite usque ad caudam porrecta”   Cinereus is “dun”, if I am right.⁵

For the power of distinguishing and consequently of naming colours has been acquired by man very late. Would you allow me to make a suggestion with respect to the colours of aquatic birds? You say Vol II. p 229: “The cause of aquatic birds having acquired a white plumage .. probably depends on their large size … Consequently sexual selection has not here interfered with or guided for the sake of protection.” When I lived on the Scilly Isles some twenty years ago I was struck by the fact that all the boats of the Coast Guard Service were painted white, and on inquiring I was told that the reason was, white boats would not so easily be seen during the dark night as darker coloured objects. I think the physical explanation is right. And if so, then the white colour of sea birds could have been acquired through natural selection for the sake of protection.⁶

As soon as the new edition of the Descent of Man is printed a new edition of the “Origin” must be prepared. Is there a new english edition in preparation or have you anything to add or alter in the fifth english edition of 1869? The same applies to the “Variation of animals and plants”, of which we are obliged to print a new edition in the course of the next year.⁷

My health is pretty well restored, although I am rather too sensible of every change of temperature. Without the Descent of Man and your great kindness I should not have been able to do as much as I have done. So you will easily believe how gratefully we are always thinking of you.

Believe me | My dear Sir | Yours most sincerely | J. Victor Carus

P.S. | Mr Koch, the publisher, proud as he is of publishing your works, asks me if he could not publish a new translation of your Voyage. I must confess I am not quite sure, if the ‘Journal of Researches’ has ever been translated; for the bad translation of Dieffenbach gives only an abstract. Of the Journal Part I was published 1844 Part II 1845, and Dieffenbachs translation bears the date 1844.⁸ How is that? Can you recollect, if the publisher of Dieffenbach (Vieweg in Braunschweig) has got the right of translation? In former years that was not necessary. Excuse me for troubling you so much.