158 PROCEEDINGS OP THE AMERICAN ACADRIMY. 



Other color types employed. Gray may also be produced synthetically 

 by breeding together a black and a golden-agouti animal, for all three of 

 the pigments composing the gray coat are thereby brought together in 

 the young. So far as concerns the pigment-character of the young pro- 

 duced, either parent in this cross may equally well be replaced with an 

 albino derived from parents of the pigment type indicated. Gray should 

 also result from crossing the black type with the pure yellow, or with 

 an albino of pure yellow ancestry, or from a cross between a pure yel- 

 low and an albino of black ancestry. 



Black, chocolate, and golden-agouti mice as a rule breed true ; but 

 black may be a simple dominant over chocolate, and there is some 

 evidence that a similar relation may exist between golden-agouti and 

 chocolate. Both black and golden-agouti agree in consisting partly of 

 chocolate pigment, so that the added recessive chocolate may have no 

 appreciable effect on the appearance of the heterozygous individual. 



All three of these color types may arise through a resolution of the 

 compound character, gray. A similar resolution of compound pigment- 

 characters occurs in the case of some plants, as in Mirabilis. 



Postscript. 



Since the foregoing account was written, the author has seen Cuenot's 

 third report on his experiments in breeding mice. It is gratifying to note 

 that this investigator also finds the character partial albinism in mice to 

 be recessive with respect to total pigmentation. The spotted or partial 

 albino character, he finds, is separately heritable, and may be possessed 

 potentially by an albino. Other albinos may possess the character pro- 

 ducing total pigmentation, and both pigmented and albino individuals 

 may be heterozygous with respect to the two coat characters. The re- 

 sults detailed in the present paper, therefore, completely confirm those 

 obtained by Cuenot in regard to the heredity of the spotted character. 



Cuenot also describes some experiments in crossing yellow mice with 

 other color varieties, and finds, rather curiously, that the yellow character 

 is dominant over both gray and l)lack. This result indicates a strong 

 individuality for the yellow character and strengthens the l)elief that the 

 yellow type of mouse is in origin different from the black, chocolate, and 

 golden-agouti types, and may, as Bateson suggests, be derived from an- 

 other species, perhaps Mus syUmticus. 



