20 



INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



many as 6 toes on one foot. This result is not to be explained as due to a 

 regression towards the 4-4- toed condition, but rather as due to the inter- 

 mediate condition of the heterozygote. For 80 per cent of the hybrids 

 show either the typical or the reduced D type on one or both feet, although 

 neither parent exhibits these types. 



We have next to consider the results of mating together the F, hy- 

 brids. Table 11 gives the results of all matings of this sort. 



Table 11. — Frequency of the various types of toes in the second hybrid generation between normal 

 and extra-toed races. Lettering as in table 10. 



* Includes 1 case of 3-4 toes. 



Comparing tables 10 and 11, it is at once clear that in the second 

 hybrid generation the proportion of extra-toed offspring has decreased. 

 This accords with expectation, if extra-toe is dominant, for then only 75 

 per cent would be of the dominant type in F„ while 100 per cent would be 

 of that type in F,. 



