Constitution of the White Leghorn Breed. 185 



power to repress the manifestation of black pigment in the plumage ; 

 and this power is still present, although lessened, when I2 is diluted 

 to a heterozygous condition, li, as is the case in Fi of the W. L. X 

 Black cross-breds. 



With our recognition of the fact that the W. L. cf carries inhibiting 

 factors which repress the manifestation of black in the plumage of the 

 progeny from matings with black breeds, the results of certain matings 

 lead to the question whether the W. L. in its own somatic cells, 

 possesses the elements of black pigmentation. Without now enter- 

 ing into a discussion of this point, which is considered in detail on 

 a later page, it may be said that evidence derived from breeding 

 experiments yet to be presented indicates that the W. L. cf carries 

 in its germ cells the factor or factors for black pigmentation. This 

 view will be found in harmony with the experimental results already 

 given and with others to be mentioned subsequently. 



Looking at the problem in this light the W. L. may be regarded not 

 as an actually white bird, but as a black one in which an inhibiting 

 factor prevents the black from appearing. We may then tentatively 

 assume that the W. L. cf is homozygous for black pigmentation, and 

 at the same time homozygous for the inhibiting factor. Of course, 

 were the W. L. d^ heterozygous for C, the visible results in Fi would 

 be approximately the same. 



With respect to the factor for sex, assuming a Mendelian interpre- 

 tation of this phenomenon, we may tentatively regard the W. L. d^ as 

 homozygous {ff) for the absence of the female sex factor, the 9 9 as 

 heterozygous (Ff) for F. 



We come now to the relation of the W. L. cT to the factor for 

 barring. If the W. L. carries barring at all, it might be assumed that 

 it is either homozygous {BB) or heterozygous {Bh) for this character; 

 and the theoretical results from crossing will vary with the possibility 

 which we assume to hold true. In deciding this point we may take 

 into consideration the probable manner of inheritance of barring in 

 the W. L. breed provided this breed does actually carry, more or less 

 regularly, the factor for the barred plumage pattern. Analogy with 



