MUSEUM OF COMPARATIVE ZOOLOGY. llo 



which, as in their allies, the mink and marten, and in the Carnivora gen- 

 erally, is much greater than in some other groups. The differences in 

 color claimed now and then as distinctive of different species are generally 

 either such as are evidently seasonal, or such as, like those of the form and 

 proportions of the feet, etc., would disappear in a large series. I hence feel 

 convinced of the existence of but two species of weasels in Northeastern 

 North America, and that these are circumpolar, identical with the P. vulgaris 

 and P. ermineus of the Old World. These two are always distinguishable 

 with certainty, while their representatives do not present a wider range of 

 variation in size and other characters than is currently admitted for several 

 of their congeners. More than this number being admitted, the whole 

 question as to how many should be recognized, and what constitutes their 

 distinctive characters, becomes involved in the greatest uncertainty. 



Two interesting facts in respect to color in the weasels should not in 

 this connection pass unnoticed. One is that both species generally become 

 white in winter ; apparently invariably so at the far North, and usually so 

 as far south as Northern New England, but in Massachusetts only the 

 larger one (P. ermineus) thus changes, and this not always. Still farther 

 south such a change in P. ermineus occurs only occasionally, and in the ex- 

 treme southern portion of its habitat not at all.* This whitening of the 

 pelage in winter corresponds in geographical relation to the white or light 

 gray color seen in the common wolf at the north, and the gradual darken- 

 ing of its color southward. The other fact is the usual greater intensity of 

 the yellow on the under parts in specimens from the central portions of the 

 continent, — a variation parallel with the rufous form of the common wolf of 

 the same region, and the comparatively more rufous tint of the pelage 

 seen in specimens from the same district in most continentally distributed 

 species. 



Another fact in respect to size is also noteworthy, as corroborative of the 

 general law of the larger size of the representatives of a species from the 

 northern parts of its habitat than those from the southern. The measure- 

 ments given of the length of the body by those authors who have had 

 only southern specimens for examination is seven inches for Putorius vul- 

 garis, and eight to ten inches for the corresponding measurement of Pu- 

 torius ermineus, but Richardson, whose specimens were extremely northern, 

 gives nine inches for the same measurement of the former, and eleven and 

 twelve for that of the latter.f 



* Respecting this seasonal change of color, compare the observations of Richardson 

 (Fauna Boreali- Americana), Audubon and Bachman (Quadrupeds of N. Amer.), and 

 Baird (Mam. N. Amer.). 



t Professor Baird, in order to reconcile the identiTication of Richardson's specimens 

 with his P. Richardsonii, supposes the body to have been overstretched, as he says he 

 never saw any American ermines that would measure eleven inches before skinning; 



