198 Peculiar Pigmentation of the Silky Fowl 



the pigmentation nor the inhibiting factor in either sex. These birds, 

 on our system of notation, must be represented as ppii, and the 

 possession of such a strain provided us with the means of testing 

 the constitution of the F^ (Silky x Brown Leghorn) birds in the 

 simplest and most direct way. 



The Fi </ on the hypothesis produces four kinds of gametes in 

 equal numbers, viz. fPI, fPi, fpl and fpi. Crossed with F/ppii such 

 a bird should give in both sexes equal numbers of birds with and 

 without pigment. Again among the pigmented birds there should 

 be equal numbers of deeply pigmented birds, and of birds with a small 

 amount of pigment only. Table X shows that these expectations were 

 closely realised in fact. 



TABLE X. 



Males Females 



1009 



We have also made a similar set of experiments to test the gametic 

 output of the slightly pigmented F, % (ex Silky $ x Br. L. <^). The 

 constitution of such birds on the hypothesis is FfPpIi and owing to 

 repulsion between F and / the gametes produced are of four kinds 

 only, viz. FPi, Fpi, fPI, fpl (cf p. 188). Mated with ^^ oi the 

 constitution ppii such birds should give equal numbers of pigmented 

 and unpigmeuted clucks in both sexes. And since the female gametes 

 which contain P all lack the inhibiting factor, all the % % pigmented 



Reference Ne 



1909 Pen 3, 467 i^i (slif 



1910 „ 22, 4? s iPpIi 



