120 NORTH AMERICAN MUSTELID.E. 



Now, as to the details of coloration, especially the line of 

 demarcation of the two bod.v-colors, we must remember, in the 

 beginning, that we here have an animal which, under ordinary 

 conditions, turns entirely white once every year, and resumes 

 its bicoloration as often j that consequently we must expect to 

 find skins showing every possible step of the transition ; and 

 that, moreover, various odd little matters of coloration are cer- 

 tain to appear in different cases. Taken in its perfected sum- 

 ttier dress in average latitudes, the animal ordinarily shows a 

 line of demarcation, beginning at the snout, involving the edge 

 of the upper lip, running thence straight along the side of the 

 head and neck to the shoulder ; there dipping down the fore 

 edge of the limb to the paw, returning on the opposite border 

 of the limb, running thence nearly straight to the hind leg, 

 dipping down the outside of this also, returning to the 

 perina3um, there meeting its fellow. The tail all around and 

 upper surfaces of the paws are like the back. A slight lower- 

 ing of this line would leave the end of the muzzle and the 

 whole upper lip dark, as is frequently the case, showing how 

 absurd are any distinctions based on " amount of white on the 

 upper lip'\ The line also frequently encroaches upon the belly, 

 narrowing the sulphury band. But, as might be anticipated, 

 the chief deviations from this complete summer dress are in 

 the other direction — lessening of dark area. The commonest 

 point here is whiteness of the paws, the dark spurs stopping sit 

 the wrist and ankle. Another common state is wiiiteness of 

 the anal region and under surface of the tail. Frequently 

 light patches reach irregularly up the sides of the head, par- 

 ticularly about the ears. These points may be witnessed in 

 midsummer, and appear to be purely fortuitous — that is, not 

 traces of the regular change. 



Coming now to this matter of the change, we find it under 

 several aspects. I am not now speaking of the mode of change, 

 but of the appearances presented at different stages. A fre- 

 quent state of incipient change leaves much of the snout, ears, 

 legs, and tail, sulphury-white, with considerable elevation of 

 the general line of demarcation. This progresses until there 

 may be a narrow median dorsal stripe along the whole length 

 of the animal. In this kind of change, the fur of the dark 

 parts is often found without the slighte-^t admixture of white, 

 the hairs being uniformly as dark as in summer, to the very 



