190 Peculiar Pigriientation of the Silky Foivl 



Morgan' has made observations on Cumivgia (Mollusca) distinctly 

 unfavourable to it. At present however we think it is the most 

 acceptable account of the facts ascertained both us to the heredity 

 and the variability of sexual characters. 



Br. Legh. 



['i]I'PpIV 

 gives 

 gametes 



Ipf \ 

 ipFJ 



Br. Legh. 



llppffio. 



gives 

 gametes 



I hf 

 I hf 



\ 



Fig- 4. 



The Silky Fowl normally breeds true to the fully pigmented con- 

 dition and we consequently represent the cocks and hens of this breed 

 as ffPFii and FfPPii respectively. The Brown Leghorn on the other 

 hand never produces pigmented birds and we therefore regard it as 

 being entirely without the factor P. But it possesses the inhibitor 

 factor /; and for reasons which will appear later the cock must be 

 ' Morgan, Payne, and Browne, Biol. Bull. 1910, xviii. p. 70. 



