106 ANNALS NEW YORE ACADEMY OF SCIENCES 



chocolates. The result can therefore be brought into line with those of 

 the gray-yellow crosses, but only if we treat chocolate and black in the 

 way here suggested. 



A Mauve-colored Wild Sport 



Through the kindness of L. C. Bragg, I obtained the skin of a mouse 

 caught in Colorado far removed from any possible source of contamina- 

 tion with domesticated races. Several of these mice were caught in the 

 same locality and were kept alive by Mr. Bragg for some time. All at- 

 tempts to procure others have so far failed. The color of the sport is so 

 peculiar that I believe it worth while to record it here, for we know very 

 little concerning the origin of the domesticated races of colored mice or 

 of sports of the house mouse. The general color of the mouse is yellowish 

 brown or mauve. A microscopic examination of the hair of the back or 

 sides shows the presence of black pigment granules in the proximal half 

 of each hair, and yellow pigment in the outer part, except at the tip, 

 which is colorless. In addition, some of the large hairs contain black 

 pigment nearly to their tips. Comparison with the hair of the ordinary 

 house mouse shows that the base of the hair of the mauve mouse is much 

 less black than is the ordinary hair, and that the yellow brown pigment is 

 identical with that in the yellow band of the gray mouse. The mauve 

 mouse appears, therefore, to owe its color to the loss of chocolate, and 

 perhaps to a lightening of the black color at the same time ; but the latter 

 effect may be due to the absence of chocolate in the black portion, where 

 it appears to be mixed with black in the ordinary mouse. 



The Influence of the Environment on the Color of Peromyscus 



leucopus ammodytes 



The intergradations between many of the species of Peromyscus has 

 made their identification and classification difficult. The occurrence of 

 intergrades in regions of overlap may be explained either as the result of 

 interbreeding of the more typical forms found elsewhere or as the effects 

 of the environment. Both of these questions might be studied, I thought, 

 by breeding the mice in confinement. In the winter of 1907, and during 

 1908-9, I kept several species of Peromyscus in the laboratory — species 

 from the Eastern States, from Florida, Texas, California, Colorado, 

 Indiana, Ohio and elsewhere. The results have been meager because in 

 most cases the mice failed to breed, both when like was bred to like and 

 when different species were kept together. In the summer of 1908 and 

 again in 1909, I collected tbe local races of Peromyscus found on Mono- 



