No. 615] INHERITANCE IN PEROMYSC 



189 



Since the coat color is at no point homogeneous, any such 

 comparison with uniformly tinted paper is of course very 



The desert mice are of a hue which can not even ap- 

 proximately be represented by reference to Ridgway's 

 " color standards." The effect is probably not far from 

 that which would result from a mixture of fine streaks of 

 black and of "oehraceous buff" or " cinnamon buff," so 

 proportioned as to approximate the general hue of the 

 barren soil. As in all of these races, the mid-dorsal pel- 

 age is commonly darker than the lateral. All that need 

 be said of the two collections of " gambeli" is that they 

 are intermediate between the extreme types just re- 

 ferred to. 



As a special case of the general hair color of the body, 

 though not entirely correlated with this, is to be men- 

 tioned the color of the "ankle" region. The latter, par- 

 ticularly on its ectal surface, is covered with very short 

 pigmented hairs, whose depth of shade affords another 

 feature distinguishing the average condition of these four 



I have given considerable attention to a microscopical 

 examination of the hairs of these various mice. In posi- 

 tion the pigment is of two different sorts, axial and super- 

 ficial, located in the medulla and cortex respectively. 

 A series of more or less disc-shaped, black pigment 

 bodies extend from the base of each hair throughout 

 the whole, or a considerable part, of its length. In the 

 stouter hairs, there are, in the expanded region, two to 

 four longitudinal rows of these bodies. In all cases, they 

 alternate regularly with air spaces. 



In the all-black hairs, the black pigment extends very 

 nearly to the extreme tip. In the banded hairs, a region 

 of varying length occurs in the distal half, in which the 

 black pigment gives place to yellow. The dark pigment 

 does not end abruptly, however. The dense black bodies 

 become fragmented into their component rounded gran- 

 ules, as we pass from one segment to another, first giving 



