ALLEN. — THE HEREDITY OP COAT COLOR L\' MICE. 127 



For rats, Crampe ('77) found that the wild gray type was dominant 

 over both the albino and the black-white variety in the first generation, 

 so that only gray rats were produced. A "Mestiz" (apparently a gray 

 heterozygote), one of whose parents was a wild gray rat, when bred to a 

 black-white rat, gave 4 gray and 5 black offspring, a result comparable to 

 that of Cuenot, in which black acted as a recessive character. 



It is therefore clear that the wild gray coat of the species type is 

 strongly dominant over those types obtained from it through resolution 

 of the three pigment characters. The wild gray coat also shows less 

 tendency to break up into black, chocolate, and golden-agouti than does 

 the reversionary gray coat seen in cross-breds from fancy black-white and 

 albino stock. This will be shown in detail farther on. 



2. The black type. According to the researches of Miss Durham 

 (Bateson, : 03'' ), the black coat contains two sorts of pigments, — a black 

 and a brown, or chocolate. No case was found in which black occurred 

 alone. This result I am able to confirm. The brown pigment is visible 

 in the new hairs when the black animals are moulting, but it is much less 

 conspicuous in the fully grown hairs. Since only these two pigments are 

 found in the black coat, it is natural to in(|uire what has become of the 

 third or yellow pigment. Two explanations are possible : either yellow 

 is absent because of its having become latent, or else through segregation 

 it has been lost entirely. The latter alternative seems the more probable ; 

 the evidence for and against it will be discussed later. 



In general, two black mice breed true to that color, though under some 

 circumstances it is possible to obtain chocolate animals also. The writer 

 has reared a considerable number of black-white mice and they have never 

 produced any but black-white young (except, of course, where albinos 

 appeared in consequence of the recessive occurrence of albinism in both 

 parents). Mice wholly black, which came of a house-mouse stock, also 

 behaved in a similar way, giving blacks only, among the pigmented in- 

 dividuals. A black-white mouse bred to a black mouse of house-mouse 

 extraction produces only black young, some of which may at times show 

 a trace of white at the tip of the tail or on the toes. Bateson (:03'') 

 notes a similar result in the case of self-colored blacks bred to black- 

 whites, and asks therefore if black-white may not be recessive to black. 

 As the writer has shown in the chapter on albinism, it is more properly 

 a case of dominance of complete pigmentation over partial pigmentation. 



In looking over the records given by von Guaita ("98, : GO) it is found 

 that in all cases where black mice were paired, the pigmented young 

 were black (or black-white), and a similar result was recorded by Ilaacke 



