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 (^2) were dominant whites and recessive blacks in the pro- 

 portion of 3.1 : i. When the hybrid dominant whites (FJ were 

 mated with pure recessive blacks, there were produced dominant 

 whites and recessive blacks in the proportion of i : i . When the 

 hybrid dominant whites (FJ were mated with a pure buff, they 

 gave whites and blacks in the proportion of i : i. 



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, i.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 (FJ were bred together, 

 they gave dominant extra toes and recessive (apparently normal) 

 individuals in the proportion of 3.8 : i ; when the Fj'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 i : 1.5. 



There were two exceptional cases of F 1} 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- 



