Dear Sir—

I am not sure whether you have received my thanks, my most sincere thanks, for the fifth edition of your “Origin of species” a copy of which you had the great kindness to send me some time ago.¹ I have again and again read this wonderful book with intense interest.

I hope the very severe review of your new work in the “Times” which, I hear, was written by the Duke of Argyll has not spoilt your good humour for a minute.² Although it rather struck me at first on account of the scientific clothing I soon found out that the critic is easily refutable. Wallace’s review in the Academy is by far superior and perhaps his suggestion to publish the “Sexual selection” in a separate book, which might be done in the second edition is particularly acceptable because many who refrain even from thinking on the descent of man would with pleasure stand up for your splendid deductions on sexual selection.³ This part of your imposing investigations being free from arbitrary opinions (which it is impossible to avoid in any treatise on the origin of mankind) is sure, I think, to extend and to confirm Darwinism in the scientific world. Besides Jena there is no University in Germany where your theory is so openly confessed and publicly taught by so many professors. Häckel, Gegenbaur, Dohrn, Strasburger, W. Müller, myself: we are true Darwinians, in our lectures and writings.⁴

Professor Müller begged me to send you his book on the development of the brain in the animal series. But I must postpone this because the editor has not yet sent a single early copy even to the author.⁵ I believe it contains many facts in support of your views.

I hope in a few weeks to send you my book on the blood-crystals. It is rather voluminous for a monography containing between 250 and 300 pages and three plates, but it was necessary to collect all the facts relating to this remarkable substance—the colouring matter of the blood—which is different in different species and only in some points the same in all.⁶

I shall also I hope soon have the pleasure of sending you a paper on the physiological functions of the external ear, wh⁠⟨⁠ich⁠⟩⁠ are nearly naught, contrary to what many physiologists believe. This result is in accordance with your remarks on the rudimentary nature of the concha. But how is it to be explained that only the human ear has an ear-lap? And the ears of the negroes have none.⁷

I remain, dear Sir, ever yours | truly Preyer

In your Variations etc II, 301 you state: the guinea-pig in Germany has dependent ears.⁸ I beg permission to state that this positively is not the case. I am occupied with rearing guinea-pigs since 6 years and have not seen a single individual with dependent ears.