190 Peculiar Pigmentation of the Silky Fowl 



Morgan^ has made observations on Cumingia (Mollusca) distinctly 

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

 acceptable account of the facts ascertained both as to the heredity 

 and the variability of sexual characters. 



Ilppff 



gives 

 gametes 



[t] 

 iiPPFf 



gives 

 gametes 



iPF 



iPf 



Bp. Legh. 



[^]IippFf 



gives 

 gametes 



lpf\ 



ipFj 



U]IiPpff liPfFfi^^ 



gives 

 gametes 



i IPf] 

 Ipf 



iPf 

 ipf 



gives 

 gametes 



Br. Legh. 



Ilppff 16} 



gives 

 gametes 



ilpf 



Ipf 



--V 



\ 



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 ffPPii 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 7; and for reasons which will appear later the cock must be 

 1 Morgan, Payne, and Browne, Biol. Bull. 1910, xviii. p. 76. 



