98 MENDELISM CHAP. 



pigment. None of the F 2 male birds, however, 

 showed the full deep pigmentation of the Silky. 



When, however, the cross was made the other way, 



viz. Brown Leg- 

 Brown Leghorn Silky ^ hen x snky 



I cock, the result 



i 1 1 was different. 



<$- -- F i While the F x male 



birds were almost 

 destitute of pig- 



ii <$ <$ <5 t ? ? 9"" F 2 ment as in the 

 FIG. 20. previous cross, the 



Scheme illustrating the result of crossing a Brown F henS, On the 

 Leghorn hen with a Silky cock (cf. Fig. 19). 



other hand, were 



nearly as deeply pigmented as the pure Silky (PI. V., 

 2). The male Silky transmitted the pigmentation, 

 but only to his daughters. Such birds bred together 

 gave an F 2 generation containing chicks with the full 

 deep pigment, chicks without pigment, and chicks 

 with various grades of pigmentation, all the different 

 kinds in both sexes. 



In analysing this complicated case many other 

 different crosses were made, but for the present it 

 will be sufficient to mention but one of these, viz. 

 that between the F x birds and the pure Brown 

 Leghorn. The cross between the F t hen and the 

 Brown Leghorn cock produced only birds with a 

 slight amount of pigment and birds without pigment. 

 And this was true for both the deeply pigmented 

 and the slightly pigmented types of F I hen. But 

 when the F l cock was mated to a Brown Leghorn 

 hen, a definite proportion of the chicks, one in eight, 

 were deeply pigmented, and these deeply pigmented 



