COLOR MUTATIONS IN MICE OF PEROMYSCUS 315 



Castle ('16, '20) records that ''the occurrence of yellow sports 

 among wild meadow mice (Microtus) has been observed by 

 Cole, Barrows, F. Smith and others," and Dunn (1921) lists 

 several wild rodents in which 'restricted yellow' is said to occur.^i 

 Unfortunately, no further particulars are available relative to 

 the pigmentation or genetic behavior of these. 



It is hardly necessary to point out that our 'yellows' have no 

 relation to the race of dominant yellow house-mice, which has 

 been so much discussed in genetic literature. 



Regarding the possible relationship of our 'pallids' with other 

 described color varieties of rats and mice we can speak somewhat 

 more definitely. The almost (though not quite) complete lack 

 of black pigment, together with the presence of abundant yellow 

 pigment, in the hair and the dark red color of the eyes would 

 suggest that our 'pallid' race corresponds, in some sense, to the 

 'red-eyed yellows,' discussed by Castle ('14 and later papers) 

 and others for rats.^^ This surmise is greatly strengthened by 

 the fact, referred to above, that in both species there is a high 

 degree of linkage between the factor for the red-eyed mutation 

 and that for albinism (Castle, '14, '16 a, '19; Castle and Wright, 

 '15; Dunn, '20). 



The occurrence of true albinos among Peromyscus has already 

 been recorded by Castle ('12). Castle's specimens belonged, 

 however, to a different species from ours (P. leucopus novebora- 

 censis), the progenitor of the strain having been sent him from 

 IVIichigan. Doctor Castle kindly furnished us with a pair of 

 these mice, but the latter, like all the surviving members of his 

 strain, proved to be sterile. 



The 'identity,' in terms of the factorial hypothesis, between 

 albinism in Peromyscus and that in the house-mouse cannot, of 

 course, be taken for granted. Since the crossing of these genera 

 seems to be impossible, this question can never perhaps be con- 

 clusively answered. 



21 'Peromyscus maniculatus gambeli' is included in this list. If Dunn here 

 refers to the 'yellows' discussed in the present paper, and reported earlier by 

 Sumner, he is probably not justified in assigning them to this class. 



22 First referred to as 'black-eyed yellows.' 



