ALLEN, — THE HEREDITY OF COAT COLOR IN MICE. 119 



the character total pigmentation maybe transmitted by albinos, and when 

 so transmitted dominates over the spotted condition. How this may pos- 

 sibly take i)lace, an ingenious suggestion made by Cuenot (: 03) indicates. 

 This inve.'^tigator believes that the formation of pigment is due to the 

 action of some ferment upon a chromogenic substance, and that an albino 

 may transmit the former apart from the latter. It might be that the 

 gamete of such an albino brings in a quantity of the ferment suihcient to 

 produce a greater amount of pigment, and so the resulting individual is 

 much less marked with white than the spotted parent. Such considera- 

 tions are, however, purely theoretical. 



If* the character total pigmentation be dominant, in the Mendelian 

 sense, over partial pigmentation, it should be possible by interbreeding 

 heterozygous individuals to obtain 25 per cent of offspring having the 

 spotted character. Of the 75 per cent of self, or wholly pigmented 

 animals, one-third are expected to be pure in respect to the character 

 total pigmentation, and the remainder to be heterozygous. 



From the writer's self-colored heterozygotes (Fi) obtained by crossing 

 black-white mice with albinos which transmitted the character total pig- 

 mentation, a second generation was bred, consisting of 10 spotted, 27 

 nearly nnicolor, and 15 albino young. As the albino young were not 

 tested to discover which of the two pigment characters they transmitted, 

 it is necessary to disregard them. Of the 37 pigmented animals, there- 

 fore, one-fourth, or 9, are expected to be spotted, and there were actually 

 10 of that nature. Von Guaita in his generation Fj, which was ob- 

 tained in a similar manner, got 10 spotted and 20 self-colored individuals 

 from the heterozygotes, an excess of 2.5 spotted young over the expected 

 number. Darbishire (: 03) records a similar case. He intercrossed spotted 

 Japanese dancing mice with albinos of two stocks, the one pure bred, 

 the other cross-bred. The latter sort had " appeared from time to time 

 in the litters of piebald mice kept in the Oxford Laboratory for embryo- 

 logical purposes " ; the former were purchased of a dealer. The cross- 

 bred all)ino3, since they are presumably of spotted parents, will transmit 

 the spotted character, so that Darbishire's result, 25 spotted and 4 

 unspotted young, is quite what might be expected. The four unspotted 

 individuals probably came from au albino which was heterozygous with 

 respect to the two characters, total and partial pigmentation. From his 

 pure-bred albinos, Darbishire obtained 36 spotted and Gl unspotted mice, 

 a fact indicating that at least some of these albinos transmitted the char- 

 acter making for total pigmentation. The result is due apparently to the 

 transmission of pigmentation characters through the albinos, not to the 



