574 THE AMERICAN NATURALIST [Vol. LVI 



his mutant with these forms. Dr. Detlefsen's form is evidently 

 lower in the scale running from color to complete albinism in 

 very much the same way that the Himalayan form is nearer to 

 the albino than is the chinchilla rabbit. 



The new mutant was procured from a fancier who had been 

 breeding it for some time. It resembles the ruby-eyed guinea 

 pig, ruby-eyed rat and the ruby-eyed or chinchilla rabbit 

 (Castle '21)^ in the degree of pigment reduction in the hair, 

 but the eyes are apparently darker than those of the rat and 

 guinea pig. I have not had an opportunity to examine the 

 eyes of the chinchilla rabbit. It forms one of a series of quad- 

 ruple color aHelomorphs in the mouse and may be designated 

 as c''. In a scale of dominance, the four forms probably fall 

 into the following order: ordinary intense or wild color, C; 

 dilute, C (described in this paper) ; extreme dilute, c** (de- 

 scribed by Dctlefsen ('21); -^ and complete albinism, c. Wild 

 color ((;) is completely dominant to the other allelomorphs, but 

 C and c-^ are incompletely dominant to albinism. The cross 

 between C and C' lias not yet been made, but the heterozygote 

 (c'o'O will probably be found to give an intermediate shade. 



The black agouti type of the homozygous mutant {AABBc'-cn 

 possesses black pigment which is reduced to a very dark dull 

 slate-color, while yellow is greatly reduced aiul appears about 

 intermediate between wliite and the normal yellow of the wild 

 type. In tlie non-agouti type of the homozygous mutant 

 {aaBBc'c'), which can be distinguished readily from the agouti 

 form, the black pigment is also reduced to a very dark dull 

 slate-color, but perhaps darker than in the agouti type. 



When the black agouti type of the mutant is heterozygous 

 for albinism {AABBc'c), black pigment is reduced to a brown- 

 ish shade and yellow is practically reduced to white. In the 

 non-agouti type of the heterozygous mutant {anBBc^c), black 

 is reduced to a dull browu, a little liuhter than the ordinary 

 fam-i^Ts chdcilati^ ty])r. The liet(T(tzy<:ous mutants, mated 

 inttTM'. pnnliiri' ilir li( -ioiis TyiM", tiic heterozygous type 

 and idhinos m the I'atu. 1:2:1. 



T have lint \v\ identified th<^ mutfint without black pigment 

 that is in the cinnamon or brown class. 



II. W. Feldman 



