ALLEN. — THE HEREDITY OF COAT COLOR IN MICE. 



67 



and black young. By interbreeding the gray heterozygotes (or hybrids) 

 there was produced, in addition to gray and black offspring, an occa- 

 sional golden-agouti or a chocolate individual, these two sorts being 

 about equally numerous. A similar result was obtained by crossing a 

 gray with a black heterozygote, but these same black heterozygotes when 

 bred inter se produced only blacks. 



It is probable that the various color varieties of mice, as now kept by 

 ftinciers, have originated through segregation of elements found in the 

 compound gray character, caused perhaps by crossing with dissimilar 

 varieties. Long domestication and the conditions incident to confine- 

 ment have very likely been effective in aiding this so-called *'■ break- 

 ing up of the type." 



It may be of interest to mention here what appears to be a patho- 

 logical variety of the house mouse, namely, the so-called "rhinoceros 

 mouse." This appears to 

 have first been figured and 

 described by Gaskoin ('56), 

 whose colored plate repre- 

 sents an animal of the size 

 of the common mouse, but 

 entirely devoid of hair, 

 except for a few whisk- 

 ers. The skin, however, is 

 thrown into a series of trans- 

 verse corrugations, and ex- 

 tends along the sides as a 

 broad fold running from the 

 anterior to the posterior 

 limbs and loosely envelop- 

 ing them. This character and the generally wrinkled appearance of the 

 skin give the animal somewhat the appearance of a diminutive rhinoceros. 

 According to Gaskoin, no vestige of hair or hair follicles could be discov- 

 ered in microscopic sections of the skin. He states that two individuals 

 of this sort, a male and a female, were captured by a laborer about a straw 

 stack which stood in a wood not far from Taplow Paper Mills, England. 

 The female was pregnant and in a week had five young, all of which 

 were of the same "rhinoceros" type. Gaskoin also mentions a similar 

 specimen which was captured in the fireplace of a room, in 1820, and is 

 preserved in the museum of the College of Surgeons, England. 



The present writer obtained a mouse exhibiting this same condition 



Figure 1. 



