356 



MR. J. T. CUNNINGUAM ON 



number piles and half black-reds. At the same time it is to be 

 noted that the pile coloration in these birds was more pronounced 

 and more uniform than in the heterozygotes of F^, whereas if 

 the F., mothers had been pure dominants, there is no reason why 

 the offspring of F., DD's with the RR black-red should have any 

 more colour than the DR's of F^. 



If we regard the dominant white as one character and the 

 black-red colour as its allelomorph, the evidence of these 

 experiments seems to show both imperfect dominance and 

 incomplete segregation. The pile produced by my cross, and 

 probably the pile of fanciers also, is a heterozygote, like the blue 

 Andalusian, and it should produce in the F^ generation whites, 

 piles, and black-reds in the proportion 1:2:1. In F^ the white 

 is not a complete dominant ; it suppresses the black colour almost 

 but not quite completely, but the red colour was developed in 

 varying degrees in the piles, eight cocks and four hens, while the 

 other three hens showed only scattered specks of blaclv and red. 



In the F, generation both groups A and B were the offspring 

 of heterozygotes, the parents of A being of the pile coloration, 

 those of B showing greater dominance of white. The two groups 

 may be compared thus : — 



F,, Group A. 



Kecessives. 



2 $ , one black and one grey, each with 



some white feathers. 



Heterozygotes. 

 5 $ deep pile to pale pile. 



3 $ dark pile to rather pale lacing. 



? Dominants. 

 2 (J very pale pile. 

 1 $ white with trace of reddish lacing 

 neck. 



F^ Group B. 



Recessives. 

 1 $ reddish brown with black specks. 



Heterozygotes. 



3 $: one moderate pile with a few black 



marks, two pale piles with spots of 

 black, or orange and black. 



4 $ : two typical piles, two j-ellow on 



head and hackle, with many black 

 spots. 



? Dominants. 



5 $ very pale piles, two with onl3' a 



slight tinge of yellow on back of 

 wings, perhaps not more than occurs 

 occasionally in Leghorn cocks. 

 4 $ white with scattered specks of 

 black or grey. 



But while, as this table shows, the recessives can be definitely 

 distinguished from the heterozygotes, it is not possible to separf^te 

 the pure dominants from the heterozygotes. In the whitest birds 

 there are some traces of colour, and the amount of colour forms a 

 continuous series from the typical pile cock and hen to the birds 

 with least colour. In the recessive hens also there are distinct 

 traces of white. The segregation therefore is imperfect. 



