31 



ish-brown to a rich mahogany brown, or mink color. Below, the animal 

 is white, tinged with sulphury-yellow, the chin, throat, and ineides of 

 the legs excepted; these being white; the line of separation between the 

 upper and lower colors is strict, and the shades nearly uniform. 



Skins taken in spring and autumn show every possible step of the 

 transition, from the perfect winter to the summer pelage, and vice versa. 

 In the winter the animal becomes (with the exceptions already men- 

 tioned) so pure a white as to be ■ emblematic. Professor Baird, in his 

 description of an arctic form of this group, says, " as an ermine, the em- 

 blem of spotless purity and integrity, I propose to call it (i. e., P. kaneii, 

 Baird) after Dr. Kane." 



Much has been written as to the mode of the change from one pelage 

 to the other, both in the Ermine, Arctic Fox, Northern Hare, Hudson's 

 Bay Lemming, and other animals, some contending that it is by the ac- 

 tual change of color of the existing fur, and that this transition from the 

 summer to the winter color is the result of actual change of temperature, 

 and not merely by the advance of the season. Audubon and Bachman 

 observed a captured specimen, from March 6th to 28th, which, in this 

 period, nearly completed the change from white to summer colors. They 

 report : " We have arrived at the conclusion that the animal sheds its 

 coat twice a year ; i. e., at the period when these semi-annual changes 

 take place." Dr. Coues concludes that the change is not altogether co- 

 incident with, nor independent of, the change of coat, but occurs in both 

 ways, temperature being the immediate controlling agent in the trans- 

 formation. Northern animals invariably change color semi-annually; 

 southern species do not change at all; in intermediate regions the 

 change is partial. Autumnal skins, having the hair white at base and 

 brown at tip, demonstrate the change in existing hairs. 



" We maj^ safely conclude that if the requisite temperature be expe- 

 rienced at the periods of renewal of the coat, the new hairs will come 

 out of the opposite color ; if not, they will appear of the same color, and 

 afterward change." (Coues.) 



The changes in color screen the Ermine from enemies, and from its 

 prey also, by assimilation of its appearance with the surroundings ; 

 moreover, the animal heat from within is more completely retained by a 

 white than by a dark covering, although not so much warmth is received 

 during direct exposure to the sun's influence. 



Winter specimens are white, as a rule, in the northern line of States, 

 and northward. Prom the southern States no white specimens are 

 quoted. In the inter- region, some may change and others not ; and the 



