124 Experimental Zoology 
The black plumage of the Houdan and the Hamburg domi- 
nates over the buff of the Cochin, but incompletely, the black 
being marked and shaded with brown. 
When the hybrid dominant whites (F;) were mated, the off- 
spring (F,) were dominant whites and recessive blacks in the pro- 
portion of 3.1 :1. When the hybrid dominant whites (F',) were 
mated with pure recessive blacks, there were produced dominant 
whites and recessive blacks in the proportion of 1:1. When the 
hybrid dominant whites (F,) were mated with a pure buff, they 
gave whites and blacks in the proportion of 1: 1. 
The experiments in which animals with the normal number of 
toes are crossed with races having an extra toe give results of 
unusual interest. In general, the extra toe (of the Houdan) is 
dominant over the normal foot (Leghorn, Hamburg, Cochin). 
In some cases the dominance is complete, z.e. the extra toe is full 
size; in other cases all gradations in the size of the extra toe were 
found ‘‘down to the mere duplication of the nail.” The extra 
toe was found in some cases only on one foot, the other appearing 
as in the normal. There were some cases in which the normal 
foot appeared to dominate, but whether such cases are real 
dominance of the normal, or the failure of the extra toe to appear 
in an individual that has it potentially present can only be deter- 
mined by subsequent breeding. 
When the dominant extra-toed hybrids (F,) were bred together, 
they gave dominant extra toes and recessive (apparently normal) 
individuals in the proportion of 3.8: 1 ; when the Fy’s were bred 
to pure recessives without extra toes, they gave dominant extra 
toes and recessives, apparently without extra toes, in the propor- 
tion of 1: 1.5. 
There were two exceptional cases of F,, in which the normal 
foot seemed to dominate. These were a male and a female. 
When mated they gave 22 chicks, of which 14 had an extra toe 
and 8 had normal feet. The result shows that the parent birds 
are really RD’s, since chicks with extra toes appeared when the 
birds were bred together. This conclusion was confirmed by 
breeding the cockerel to another pure individual with (reces- 
