19-21.] 



Research in Animal Breeding. 



329 



is evidence too that some factor leading to increased milk yield 

 in cattle is transmitted on the same Hnes. Here, however, sex- 

 iinked transmission is by the bull, not by the cow. For cattle, 

 like men, are mammals, and it is probably the male in mammals 

 that produces two kinds of sperm differing in their sex-deter- 

 mining properties, while the female produces only one kind of 

 ovum. The bull may transmit something to his daughters 

 that he does not transmit to his sons. 



The Cambridge work has also included another serie.- of 

 experiments dealing with a character of which the transmission 

 is closely wi-apped up with that of sex. In certain breeds of 

 poultry the cock is feathered like the hen. He lacks the long 

 hackles of the neck and saddle, and the curved tail sickles of 

 the normal male, their places being taken by feathers such as 

 are normally found in hens. This feature of henny feathering 

 in the cockerel is found in Sebright Bantams. Campines. Henrv 

 Game, and occasionally also in other breeds such as the Ham- 

 burghs (see Plate 1. Fig. 1>. Tn our experiments the character 

 was introduced by means of the Sebright Bantam. We found 

 that henny feathering was dependent upon a definite factor, 

 and that henny feathering in the cock is dominant to normal 

 feathering. In its first plumage the henny cock may be inter- 

 mediate between henny and normal feathering, but when this 

 is the case he takes on the henny plumage at his first moult. 

 Either sex in henny breeds can transmit the henny factor. From 

 a bird of a pure henny breed, whether cock or hen. crossed with 

 a bird of a normal breed, all the cocks produced are hennv. The 

 hens, however, are like normal hens in appearance, noi- is it 

 possible to distinguish hens which transmit henny feathering 

 to their sons from those that do not. The interesting point then 

 arises as to how we are to regard normal breeds where the hens 

 are hen-feathered and the cocks are cock-feathered. A marked 

 step towards the solution of this problem was made by Pezard 

 in France, and Goodale in America. Both these observers 

 found that complete removal of the ovary, a very difficult opera- 

 tion, led to the castrated hen assuming cock-like plumage at the 

 moult. The obvious inference is that the normal hen is poten- 

 tially cock-plumaged. but that she forms a substance in the 

 ovary which circulates in the blood, inhibiting the development 

 of cock plumage, and rendering her henny. Further, since we 

 can attribute hennv feathering in the cock to a definite fa t^r, 

 we are led to suppose that the hen of normal breeds also carries 

 this factor, though she transmits it onlv to her daughters, and 



