Experimental Hybridizing 89 
on the belly. Haacke and von Guaita found similar results. 
“The influence of the albinos in these cases seems to be to 
upset the condition of localization of the pigment, so that the 
pigment patches become more extensive, tending to cover the 
entire body surface, as in totally pigmented animals. In expla- 
nation of this observation it is suggested that the character 
total pigmentation may be transmitted by albinos, and when 
so transmitted dominates over the spotted condition.” Cuénot 
has offered a suggestion to account for this possibility. The 
pigment is assumed to be due to the action of a ferment upon a 
chromogene substance. The albino may transmit the ferment 
but not the substance. The germ-cell of the black-and-white 
individual would then be assumed to convey the pigment, and, 
when to it more ferment is added by the white gamete, more 
pigment is produced in the offspring. 
Cuénot has given a very clear and important analysis of his 
results with mice in his third contribution to “The Heredity of the 
Pigmentation in the Mouse.’”’* He uses the letter C to denote 
any colored character, and A for the albino character; G for 
the color gray; B for the black; and Y for the yellow. Thus 
the wild gray mouse will be represented by CG, and the ex- 
tracted albinos, having potentially the gray color, by AG. The 
black mouse will be represented by the formula CB; extracted 
albinos derived through black ancestors AB; the yellow 
mouse by CY; the extracted albino through yellow ances- 
tors by AY. 
When a germ-cell containing the character CG unites with 
one containing CB, the gray; G, dominates. When gray, CG, 
meets yellow, CY, the latter dominates. When CB meets 
CY, the yellow again dominates. When a colored germ-cell, C, 
meets an albino, A, the individual that develops has black 
eyes, but the color of the hair depends on which color accom- 
panies C or A. As an example Cuénot gives this case: a black 
mouse, CB, crossed with an albino, AY (yellow latent), gives a 
dihybrid, CBAY. This hybrid has black eyes, because for 
1 Archiv. Zool. Expér. et Gén. 1904. Sér. 4, T. z. Notes et Revue, p. xlv. 
