GrEOFFREY 8mITH AND MrS HaICt ThOMAS 45 



cases, as he cites as instances some birds with hermaphrodite internal 

 organs which obviously come into a totally different category. On the 

 whole, however, Brandt's evidence agrees essentially with Hammond 

 Smith's and our own. Mrs Haig Thomas on the other hand has in her 

 records a case of a male common j)heasant, probably about eight months 

 old, with partial female plumage, in which the testes were exceedingly 

 small, about the size of a six weeks old male chick. It seems to me 

 probable that this was a case of a late-maturing cock bird, in which 

 both male plumage and normal testes would have developed later. My 

 reason for suggesting this is that I have at present a breed of white 

 Leghorn fowls in which the cock birds fall into two classes, those which 

 assume full male plumage, spurs and comb, and which become internally 

 mature about six months after hatching, and those which it is impos- 

 sible to distinguish from hens for eight months after hatching and 

 which then gradually assume the male characters. The two characters 

 of early-maturing and late-maturing are hereditary characters which 

 appear to segregate in inheritance, but the exact nature of this here- 

 ditary transmis,sion has not yet been worked out. 



Now if the above arguments are substantiated, it would seem that 

 the appearance of the secondary sexual characters of the opposite sex 

 in the female and in the male bird may be due to two different cau.ses ; 

 in the female it appears to be due to atrophy or abnormality of the 

 ovary, and in the male to a transference of the female plumage inde- 

 pendently of any abnormality of the testes. The case of the female is, 

 therefore, one of correlated differentiation, where the atrophy of the 

 ovary liberates some stimulus for the development of the male charac- 

 ters, while the case of the male is due to hereditary transference, wheie 

 a particular set of female secondary sexual characters are transferred 

 to the male without the structure or function of the testes being 

 affected in any way. 



That such hereditary transferences of secondary sexual characters 

 from one sex to the other often occur, without the normal reproductive 

 capacity of the individual being affected, is well known: common 

 instances are the hen-plumage of the Sebright Bantam cocks, and the 

 appearance of spurs in the females of many breeds of fowls. In both 

 these cases the males and females are perfectly normal reproductive 

 individuals ; all that has happened to them is the transference in 

 heredity of a particular group of secondary sexual characters which 

 properly belong to the opposite sex. 



We must, therefore, clearly distinguish between two entirely 



