Studies on Inheritance in Poultry. 
451 
pigment is dominant over its presence. We are forced to conclude 
that the White Leghorn and other breeds, such as the White Dorking, 
characterized by the D-white, must contain some pigment-destroying 
or pigment-neutralizing character which prevents the manifestation 
of black. The exact nature of this character is unknown, but it 
may be referred to merely as an inhibiting factor (I), for which the 
White Leghorn appears to be homozygous. It may be similar to the 
inhibiting factors (Wi, W 2 , W 8 , etc.) which Cole* finds present in 
pigeons. 
The manner in which this factor acts, in order to destroy pigment, 
or to neutralize it, or to prevent its formation, is at present a matter 
of speculation only. One might assume that there is some funda¬ 
mental color-substance (C) upon which various color-enzymes act 
to produce, one black, another red, another buff, etc. Black pig¬ 
mentation for instance, might be regarded as the result of a color 
enzyme (N, nigrum) acting upon the general color factor C.f Thus, 
without knowing what factors for pigmentation actually are, it 
serves our present purpose to assume that one or more factors are 
necessary for the production of black pigmentation and that the 
inhibitor, I, through its action upon one or all of them, is able to 
repress such pigmentation, not only in the White Leghorn itself 
(provided the factor, or factors, concerned could otherwise determine 
black pigmentation), but also in Fi in crosses between the White 
Leghorn and other breeds characterized by black plumage. 
One other character which is possessed by the White Leghorn and 
which affects the results of crossing in F 2 , must be mentioned. This is 
the barred plumage pattern which, as the writer has already shown, + is 
commonlj' latent in the White Leghorn stock. The White Leghorn cf 
used in the cross about to be described was homozygous for this 
character (BB) while the White Plymouth Rock $ 9 were heterozy¬ 
gous (Bb). In accordance with results of studies on barring, carried 
*Cot,E, I.. J., Studies on inheritance in pigeons: I. Hereditary relations of the principal colors, 
R. I.Agr. Expt. Sta. Bui. 158,1914. 
tDAVENPORT, C. B., Inheritance of characters in the domestic fowl, Publ. No. 52, Carnegie Inst., 
Washington, 1906. 
JStudies on inheritance in poultry.: I. The constitution of the White Leghorn breed, Rhode 
Island Agr. Expt. Sta. Bui. 155, pp. 151-216. 
