50 



INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



The distribution of table 35 is characterized by its large variabiHty. 

 Although the numbers are small, there are evidences of two modes, one 

 between grades 3 and 6, and the other at from 8 to 10; these evidently 

 correspond to the modes of the typical Silkie and the typical Cochin respec- 

 tively or to DR and RR types of booting respectively. The distribution of 

 table 35 is additional evidence of the heterozygous nature of the Silkie boot. 



We are now in a position to consider the effect of back crosses (table 36) . 

 The contrast between the totals in tables 36 and 37 is very great. The 

 strict Mendehan expectation is: in the DR xD crosses 50 per cent DD 

 (clean-footed) and 50 per cent heterozygous, which, with imperfect domi- 

 nance, might be expected to show foot-feathering. Actually about 46 per 

 cent are clean-footed. In the DR X R crosses expectation is that 50 per 

 cent certainly (the extracted recessives) and 50 per cent more possibly will 



