CONTINUOUS AND DISCONTINUOUS VARIA- 

 TIONS AND THEIR INHERITANCE IN 

 PEROMYSCUS. Ill 



DR. F. B. SUMNER 

 Scripps Institution. La Jolla, Calif. 

 VII. Mutations 

 In a recent paper (1917a) I have described two widely 

 aberrant color types which have appeared in my cultures, 

 together w T ith certain minor deviations, which likewise 

 seem to behave as discontinuous variations. I am pre- 

 pared to add considerably to the data thus far published. 



L "Partial albinos" 

 The term albino, as applied to these mice, admittedly 

 does not conform to current usage, and this has become 

 especially evident with the appearance of the mature pel- 

 age. I do not think, however, that any of the various 

 names given to fancy races of Mus musculus apply to 

 these animal-. Having at hand no specimens or even 

 satisfactory colored plates of fancy mice, I am unable to 

 make the comparisons. 27 As previously stated, this mu- 

 tant strain has red eyes, and lacks pigment wholly on the 

 ears and tail. The fur, on the colored region of the body, 

 is a very pale gray, rather strongly tinged with a shade 

 of yellow approaching Ridgway's "ochraceous buff," or 

 perhaps "oehraceous orange," on the most highly col- 

 ored areas. As a convenient non-committal expression, 

 I shall henceforth employ the term "pallid" for these 



A microscopic examination of the hairs of these mice 

 reveals some interesting departures from the normal con- 

 dition: 28 (1) a considerable proportion of the hairs are 

 practically devoid of pigment in the zone which is ordi- 

 narily yellow, while the rest are normal in this respect; 



2t It may be that the factional modifications of ray mice are the same as 

 those of Castle's "red-eyed yellow" rats (see Castle and Wright, 1915). 



439 



