FUTURE OF THE SCIENCE OF BREEDING 173 



portion of the problem of sex. Equally arresting in the 

 scheme of things are those characters which, normally the 

 property of one sex, are upon occasion appropriated by the 

 other. The hind may sprout antlers, the cock may become 

 broody or the woman may grow a beard. The study of these 

 secondary sexual characters, characters not directly concerned 

 with the primary function of reproduction, is becoming a sub- 

 ject of genetic inquiry. We cannot yet claim that great pro- 

 gress has been made, but the following example may serve to 

 indicate the lines along which such inquiries are being directed. 



In certain breeds of poultry the plumage of the cock 

 resembles that of the hen. He is destitute of the long, 

 silky and often brightly coloured feathers on the neck and 

 back which are generally associated with this sex, nor has he 

 the usual curved, flowing sickles in the tail. Breeding experi- 

 ments have proved that " henny " feathering in the cock is 

 dominant to normal cock feathering. The " henny " cock 

 contains some factor which prevents the development of the 

 normal cock plumage. What of the hen ? Is her plumage 

 " henny " because she also contains this factor ? And in 

 normal breeds do we get " cocky " cocks and " henny " hens 

 because this factor is somehow sex-linked and transmitted 

 to the hens alone ? 



That this is a reasonable way of looking at the matter 

 is evident from the remarkable experiments of Goodale and 

 of Morgan in America. Those of Goodale deal with the 

 effects of castration in a breed of fowls, the brown Leghorn, 

 in which the sexes differ markedly from one another in 

 plumage. In the male the operation produces practically 

 no effect ; the feathering after moulting is as before. But 

 removal of the ovary from the hen, an exceedingly difficult 

 operation, led to a marked and surprising result. Such a bird 

 may moult into the full cock plumage, though the general 

 habit of her body remains that of a hen. The castration story 

 agrees with the conception of the hen being potentially cock- 

 plumaged but unable to show it owing to the possession of a 

 factor which inhibits the development of such plumage. And 

 it adds something further ; for we must suppose that the 



