156 Hybrids between Pheasant and Fowl 



All the chicks, however, were males. There is a possibility that the 

 absence of females was accidental and that the males are rifiore viable 

 than the females, which died in the shell : indeed in support of this 

 Mr Lewis Jones says that he thinks he was able to identify one of the 

 offspring, which died soon after hatching, as a female. 



The well-marked colour varieties present a very complicated, but 

 interesting problem. There are two breeds of Campine fowl, silver and 

 gold, which differ from one another in the fact that the silver race possesses 

 a dominant sex limited (sex linked) character that is absent in the gold 

 race. The silver female transmits therefore this dominant factor for 

 silver only to her sons, while the gold female transmits a recessive gold 

 factor to the offspring of both sexes. Since the female parent of the 

 hybrid chicks was a Gold Campine, the existence of the two distinct 

 colour varieties cannot be explained by assuming the presence of the 

 silver factor in some, but not in others of the offspring. If, however, 

 the fact that all the hybrids reared were males is not due to the mor- 

 tality of the female embryos, but is caused by the development into males 

 of eggs which, if normally fertilised by sperms of their own species 

 would have been females ; then it is possible that the two colour classes 

 of hybrids may be due to the presence of some other sex limited factor 

 derived from the Gold Campine female parent. Such a factor would 

 normally be transmitted to the male offspring only and not to the female ; 

 but if the potentially female eggs are transformed into males by the 

 pheasant spermatozoa, then in this way two colour classes might arise 

 among the hybrids. 



Methods. 



The tissues were fixed in Bouin's formal-picro-acetic mixture and in 

 corrosive sublimate. Both these fixatives gave very satisfactory results, 

 but the former seemed to be a little the better of the two. A large 

 variety of stains were employed, but Heidenhain's Iron Haematoxylin 

 was much superior to them all. 



At an early stage in the work it became obvious that it would be 

 necessary to study the spermatogenesis of the parents used in the cross. 

 This I was able to do owing to the kindness of Mrs Haig Thomas and 

 Mr Lewis Jones, who supplied me with pheasant and campine material. 



