184 Bulletin No. 155.— 1913. 



It seems probable that we have to deal with at least four different 

 factors: (1) a factor for black pigmentation, C*, (2) a factor for the 

 inhibition of pigmentation, I; (3) a factor for sex (F, female; f, 

 male) ; and (4) a factor for barring, B. 



With reference to these factors, what then is the zygotic con- 

 stitution of the black 99? First, we can assmiie that they are 

 homozygous for black pigmentation {CC)*; second, that they are 

 homozygous for the absence of barring (hb); further, that they are 

 homozygous for the absence of the inhibiting factor (ii) which factor, 

 in the case of the W. L., as will appear, prevents the black pigment 

 from showing. Finally, we will assume that they are heterozygous 

 for the female sex (Ff). The zygotic formula of these birds could 

 therefore be written C2h2Ffi2- 



Making use of these symbols we may now consider the zygotic 

 formula for the W. L. cf • The W. L. breed of fowls is usually re- 

 garded as a ''pure" white variety, sometimes called the dominant 

 white or D-white, since in matings with dark birds the white appears 

 to dominate over black. But, if we regard the white plumage as an 

 absence of pigvicntation it is manifestly illogical to say that the absence 

 of a character can be dominant over its presence. Therefore another 

 explanation must be sought for the apparent dominance of white, 

 and we may assume with Bateson and Punnett {op. cit.) that the 

 dominance of white is due to the inhibiting factor /, which has the 



*It appears from the work of Bateson and Punnett (1908) on the D-whites and the R-whites, 

 that black pigmentation in poultry nuiy not always be due to a single factor. There may be present 

 a general factor for color, C, and in addition factors for special pigmentations, such as buff, red or 

 black. The latter, as suggested by Davenport and others may be conceived of as partaking of the 

 nature of an enzyme, which, as a result of its action upon C, produces the color in question. Ac- 

 cording to this view the presence of both factors would be required if the bird is to show pigmenta- 

 tion. For instance, with reference to the inheritance of color in birds possessing two kinds of pig- 

 ments, wc might need to consitler three sorts of factors: the general color factor, C, and two 

 special color factors, which working upon C, might produce, the one red, the other black pigment. 

 The explanation of color-inheritance in poultry may eventually be found not even so simple as 

 this; but it is apparent from results already attained that, as in the case of the inheritance of certain 

 colors in the sweet pea, several factors may be involved. In the present ease, however, we are 

 concerned on the one hand, only with the presence of black pigmentation (or its potential possibility 

 of appearance, other factors permitting) and, on the other hand, with the apparent absence of black. 

 For this reason, and to avoid complexity, it will be sufficient for present considerations to assign 

 to the black pigmentation a single factor, and this we will term C, with the understanding that in 

 reality this character may be dependent upon the action of two factors instead of one. These 

 might be compared with the factors which Davenport (1909) calls C and X; or to factors which 

 Bateson and Punnett (1908) refer to as X and Y. 



