My dear Sir

I am very much obliged to you for your kindness in writing to me & for sending me the pamphlets.¹ If you can at any time find out about the relative size of the eyes of the Cave Rat, it would be a very great favour.—²

You cannot tell how much your paper on Gestation has interested me.³ How facts do beat the wildest imagination! The case of the frogs has interested me particularly, because some time since I read up what I could find on subject, thinking it a good case against my notions, from absence of transitional states; but now your case is something on the road. But the unfortunate male fish with the load of eggs in their mouths exceeds everything;⁴ & what a curious fact about the foreign eggs in the mouths of some.⁵ It is quite a pity that there are not fish of the same group with cuckoo-like habits; your fact would so well have explained how the habit might have arisen.—   Speaking of transitions M^r MacDonnell of Dublin writes to me that he has made some curious discoveries on the electrical organs of the Rays,⁶ being led thereto by trying to make the case of the Electrical organs, already so very difficult to me, still more unpleasant; but as I understand him his new facts help my views considerably.—

I am very glad to hear that you are collecting facts on the “Bull-dog” fish: I suppose & hope you will bring in about the Nâta cattle.⁷ I am now at work in bringing out a Corrected Edition of the “Origin” & I will do myself the great pleasure of sending you a copy when it is published: I could not resist giving briefly your Hog case.⁸ By the way I have received another analogous fact in case of Horses.—⁹

I once saw several years ago D^r Ackland, & was charmed with him: I am pleased to hear that he defended me against so redoubtable an opposer as Agassiz.¹⁰ I was rather surprised that the latter did not attack me with more skill.—

Will you kindly forward the enclosed to Prof. Silliman by any opportunity: the note is merely to thank him for so kindly writing & giving me information.—¹¹

Pray believe me, My dear Sir, with sincere thanks & respect | Yours very truly. | C. Darwin

If you ever write again to me, can you refer me to any paper on the Rattle of Rattle-snake; I want to see some account of the tip of tail in the young before the skin has ever been moulted; & the relation of the rattle in the old to the act of moulting. I want to see what relation there is to the tail ⁠⟨⁠of⁠⟩⁠ Trigonocephalus, the habits of which I mention in my Journal as Vibrating its tail.—¹²