My dear Sir

I thank you sincerely for your letter,¹ & am heartily glad to hear of R.S. making so good a move.² I am, however, not sanguine of success.— The present plan is to try whether any existing breeds happen to have acquired accidentally any degree of sterility;—but to this point hereafter.³ The enclosed M.S. will show what I have done & know on the subject. Please at some future time carefully return the MS. to me.⁴ If I were going to try again, I would prefer Turbit with Carrier or Dragon.—

I will suggest an analogous experiment, which I have had for two years in my Experimental book with “be sure & try”.⁵ but which as my health gets yearly weaker & weaker & my other work increases, I suppose I shall never try. Permit me to add that if 5£ would cover expences of experiment, I sh^d. be delighted to give it & you could publish result if there be any result.⁶ I crossed Spanish Cock (your bird) & white Silk hen & got plenty of eggs & chickens; but two of these seemed to be quite sterile.⁷

I was then sadly overdone with work but have ever since much reproached myself, that I did not preserve & carefully test the procretive power of these hens.— Now if you are inclined to get a Spanish Cock & a couple of white Silk hens, I shall be most grateful to hear whether the offspring breed well; they will prove, I think, not hardy; if they sh^d. prove sterile,, which I can hardly believe, they will anyhow do for the pot.—

If you do try this; how would it be to put a silk cock to your curious silky Cochin Hen; so as to get a big Silk breed; it would be curious if you could get silky fowl with bright colours— I believe a silk hen crossed by any other breed never give silky feather. A cross from Silk Cock & Cochin Silk Hen ought to give silky feathers & probably bright colours.—

I have been led lately from experiments (not published) on Dimorphism to reflect much on sterility from Hybridism & partially to change the opinion given in Origin.⁸ I have now letters out enquiring on following point, implied in the experiment, which seems to me well-worth trying, but too laborious ever to be attempted.⁹ I would ask every Pigeon & Fowl Fancier, whether they have ever observed in the same breed, a cock A paired to a hen B, which did not produce young. Then I would get cock A & match it to a hen of its nearest blood; & hen B to its nearest blood. I would then match the offspring of A (viz a, b, c, d, e) to the offspring of B, (viz f, g, h, i, j)—& all these children which were fertile together should be destroyed until I found, one, (say a) which was not quite fertile with (say i). Then a & i sh^d. be preserved & paired with their parents A & B, so as to try & get two families, which would not unite together; but the members within each family being fertile together. This would probably be quite hopeless; but he who could effect this, would, I believe, solve the problem of Sterility from Hybridism.—

If you sh^d ever hear of individual fowls or pigeons which are sterile together, I sh^d. be very grateful to hear of case. It is parallel case to those recorded of a man not impotent long living with a woman who remained childless; the husband died & the woman married again & had plenty of children. Apparently (by no means certainly) this first man & woman were dissimilar in their sexual organisation.¹⁰ I conceive it possible that their offspring (if both had married again & both had children would be sexually dissimilar like their parents or sterile together.—

Pray forgive my dreadful writing; I have been very unwell all day, & have no strength to rewrite this scrawl.— I am working slowly on, & I suppose in 3 or 4 months shall be ready for M.S. of Fowls.¹¹

My dear Sir | Yours very sincerely | C. Darwin

I am sure I do not know whether any human being could understand or read this shameful scrawl.—