82 H. H. COLLINS 



1. The dorsal median region of the head from the tip of the 

 snout to the base of the skull. 



2. The hips and thighs. 



3. About 1 sq. cm. between and anterior to the forelimbs. 



4. About 1 sq. cm. in the midventral region, just anterior to 

 the hind limbs. 



Although individual differences were in some cases quite 

 noticeable, in general the mode of replacement on the depilated 

 areas was much the same. 



The history of one brood (offspring of 9 106) may be regarded 

 as fairly typical. The three members of this brood were oper- 

 ated upon, as outlined above, at the age of eighteen days. At 

 that time they were in full juvenal pelage. Without exception, 

 the skin of the posterior half of the dorsum was still dark — an 

 indication that the growth of the juvenal hair was still in prog- ^ 

 ress.^ The denuded areas on the head and ventral surface, 

 however, were devoid of pigment. 



Two days later, the pigment in the skin of the dorsum had 

 ahnost entirely disappeared, except on the exposed area on the 

 hips. Here a rather striking effect was observed. The skin 

 was as dark as when the pelage was first removed, the line of 

 demarcation between the two areas being very clearly defined. 



On the seventh day, the exposed skin on the head was begin- 

 ning to darken. That of the hips was somewhat lighter than when 

 last observed, though it was still much darker than the surround- 

 ing skin. On the ventral surface, there was a slight darkening of 

 the skin of the posterior area. 



Ten days after the operation, the pigment in the skin of the 

 depilated region on the hips had not wholly disappeared. In the 

 meantime the exposed skin on the head had become much more 

 intensely pigmented. The throat patch remained flesh color, 

 while the posterior ventral area was slightly darkened. 



WTien the brood was examined on the seventeenth day, some 

 rather marked individual differences were noted. In one case 

 the depilated area on the head was entirely covered with post- 



* Normally, the pigment disappears and the skin becomes flesh color after the 

 hair attains its full length. 



