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." Cuenot 

 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. 



Cuenot 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." 1 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 F 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 A Y. 



When a germ-cell containing the character CG unites with 

 one containing CB, the gray, G, dominates. When gray, CG, 

 meets yellow, CF, the latter dominates. When CB meets 

 CF, 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 Cuenot gives this case : a black 

 mouse, CB, crossed with an albino, A Y (yellow latent), gives a 

 dihybrid, CBAY. This hybrid has black eyes, because for 



1 Archiv. Zool. Exper. et Gen. 1904. Ser. 4, T. 2. Notes et Revue, p. xlv. 



