ALLEN. — THE HEREDITY OF COAT COLOR IN MICE. 135 



to a chocolate male, and all the seven young were black. A like result 

 was obtained in other crosses of black with chocolate mice. These 

 experiments further indicate that the albino actually transmits pigment 

 characters and is not, as might perhaps be thought, simply purified of 

 pigment characters. For if the white parent transmitted no pigment, 

 the pigmented young in this last case would have been chocolate. 



If, then, black be dominant over chocolate, it should be possible to 

 obtain ])otli black and chocolate offspring by interbreeding the hetero- 

 zygous black animals. This result was actually obtained by the writer 

 in case of two black animals which came of a cross between an albino 

 and a golden-agouti. As will be shown farther on, the black char- 

 acter doubtless came through the albino, which was of a stock known to 

 transmit this character. Tlie golden-agouti parent probably supplied the 

 chocolate character. The following diagram shows the ancestry of the 

 two black mice : 



$ wh. 9 house mouse 



$ bl.-wh. 9 wh. 



51 9 wh. S gr. 82, 84 9 gr. 81, 86 



S wh. 145 9 wh. 141 $ gr. 9 gr. 



S wh. 28G 9 gold.-ag. 224 



$ bl. 321 9 bl. 316 



In three litters from this pair of black mice, there were obtained 6 

 black, 5 chocolate, and 1 white young. If each black parent pro- 

 duced, by segregation, gametes half of which were of the black, and half 

 of the chocolate character, one-fourth of the young would be chocolate 

 and the rest black as regards their pigment qualities. Of the 12 young 

 actually obtained 5 were chocolate (3 being expected). The single 

 albino which occurred was not tested to determine in which pigment 

 category it should be placed. Additional evidence that chocolate is 

 recessive toward black is afforded by the following cross. A black 

 mouse, itself a cross between a black and a chocolate, and hence assumed 



