224 EVOLUTION [CHAP. Ill 



Letter 153 was then sadly overdone with work, but have ever since much 

 reproached myself that I did not preserve and carefully test 

 the procreative power of these hens. Now, if you are inclined 

 to get a Spanish cock and 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 should prove 

 sterile, which I can hardly believe, they will anyhow do for 

 the pot. If you do try this, how would it do 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 gives silky feathers. A cross from Silk cock and 

 Cochin Silk hen ought to give silky feathers and probably 

 bright colours. 



I have been led lately from experiments (not published) 

 on dimorphism to reflect much on sterility from hybridism, 

 and partially to change the opinion given in Origin. I have 

 now letters out enquiring on the following point, implied in the 

 experiment, which seems to me well worth trying, but too 

 laborious ever to be attempted. I would ask every pigeon 

 and 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 and match it to a hen of 

 its nearest blood ; and 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.,/, g, //, /, /), and all those children which were fertile 

 together should be destroyed until I found one say a, which 

 was not quite fertile with say, i. Then a and i should be 

 preserved and paired with their parents A and B, so as to 

 try and 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 should ever hear of individual fowls or 

 pigeons which are sterile together, I should be very grateful 

 to hear of the case. It is a parallel case to those recorded of 

 a man not impotent long living with a woman who remained 

 childless ; the husband died, and the woman married again 

 and had plenty of children. Apparently (by no means 

 certainly) this first man and woman were dissimilar in their 

 sexual organisation. I conceive it possible that their offspring 



