494 THE AMERICAN NATURALIST [Vol. LIV 



irom a wide white belt covering all of the back from 

 shoulders to hind limbs (about 45 or 50 per cent, of 

 the dorsal surface) down to a small spot located like- 

 wise on the back within this same area. The rest of the 

 dorsum including the face is colored. The belly is 

 spotted with white as in ordinary piebalds. Several 

 good examples of this type have been saved and a few 

 matings have been made recently. Only two matings of 

 belted by belted have produced young. All of these 

 young (four in number) are belted, with no spotting else- 

 where on the dorsum. This is hardly a sufficient test of 

 the separateness of this type, but more data are being 

 accumulated. 



It seems fairly evident that the production of the pat- 

 tern of piebald mice is due to a complex of genes modi- 

 fying the expression of one main gene. It is probable 

 that each such gene in the complex determines the non- 

 development of pigment in one part of the pelage. As a 

 means of testing these hypotheses and of separating, if 

 present, the various causative factors, the inbreeding 

 method advanced by East warrants a trial as the most 

 likely to bring results. Piebald mice of several different 

 types should be inbred and the inbreeding continued in 

 the various lines, brother to sister, for seven or eight 

 generations. This should result in the purification of 

 the types by the elimination of heterozygotes, and the 

 resulting pure recessives should exhibit, if present, the 

 effects of the separate factors. Such inbreeding is now 

 under way on the white face and on the belted types. 



LITERATURE CITED 



Dunn, L. C. 



1920. Independent Genes in Mice. Genetics, 5: 344-361. 

 Little, C. C. 



1914. Dominant and Recessive Spotting in Mice. Amer. Nat., 48: 



74-83. 



Little, C. C. 



1915. The Inheritance of Black-eyed White Spotting in Mice. Amer. 



Nat., 49: 727-740. 



