50 INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



Table 34. — Distribution of boot-grade in the F, generation of booted x non-booted poultry — Continued. 



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

 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 MendeUan expectation is: in the DR X D 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 



