R C. PUNNETT AND THE LATE MaJOR P. G. BaILEY 291 



among these were the few layers of the darker eggs, the difference in 

 grade between the two classes would become much more marked. It is 

 to be regretted that the layers of darker eggs among the birds recorded 

 as non-broody were not more thoroughly tested for broodiness, by 



Fig. 13. Distribution of grades of egg-colour in the F2 non-broody birds 

 ex Brown Leghorn 9 x Langshan ^J. 



keeping them for several years, and we hope that this will be done by 

 anyone who undertakes experiments on similar lines. 



That the deeply coloured egg may be laid by a non-broody hen is 

 clear from the case of $ 250/13, an F^ bii-d ex Langshan x Hamburgh 

 (cf. p. 288). But in this case there are some grounds for supposing that 

 the Hamburgh may carry a factor inhibiting the broody instinct. It is 

 possible that ? 250 was potentially broody, and that the manifestation 

 of the instinct was prevented by an inhibitor factor. It is clear however 

 that in practice it would be possible to establish a strain of non-broody 

 birds laying dark coloured eggs. 



Summary. 



1. Fi birds from a cross between a white egg laying and a dark 

 egg laying strain lay eggs of an intermediate tint. 



2. Segregation occurs in the F^ generation, the two parental grades, 

 together with all intermediate ones being found. 



3. There is evidence for the existence of an inhibitor of pigmenta- 

 tion in one of the white egg strains used, and there is some evidence 

 for regarding this inhibitor as being associated with the factor for black 

 plumage. 



