CONDITIONS OF THE CHANGE OF COLOR. 121 



roots. In other cases, however, with little or no restriction of 

 the general dark area, this insensibly lightens b}^ progressive 

 whitening of the hairs from the roots outward, at first appear- 

 ing merely paler brown, then white with brown streakiness of 

 uniform character all over. The animal finally becomes pure 

 white except the end of the tail. But this white is generally 

 tinged in places, particularly on the belly and hind quarters, 

 with sulphur-yellow. 



Conditions of the change of color. 



Much has been said of the mode in which this great change 

 is effected, not only in the case of the Ermine, but of the Arctic 

 Fox, Northern Hare, Hudson's Bay Lemming, and other animals. 

 As I have not personally witnessed the transition, I can only 

 display the evidence afforded in the writings of others. Some 

 contend that the change is rapid and abrupt, resulting in a few 

 hours, simply from lowering of temperature to a certain point. 

 Others argue that the change is gradually accomplished ; and 

 of those favoring the latter view, some maintain that the brown 

 coat is shed and a white one grown, while others hold that the 

 extinction of pigment is gradually effected without a renewal of 

 the pelage. 



We will first review the evidence adduced by the author 

 of Bell's Quadrupeds (p. 150, seq.): — ''The winter change of 

 color which this species so universally assumes in northern 

 climates .... is effected, as I believe, not by a loss of the 

 summer coat, and the substitution of a new one for the winter, 

 but by the actual change of color of the existing fur. It is 

 perhaps not easy to offer a satisfactory theory for this phenom- 

 enon, but we may perhaps conclude that it arises from a similar 

 cause to that which x:)roduces the gray hair of senility in man, 

 and some other animals ; of this instances have occurred in 

 which the whole hair has become white in the course of a few 

 hours, from excessive grief, anxiety or fear ; and the access of 

 very sudden and severe cold has been known to produce, almost 

 as speedily, the winter change, in animals of those species 

 which, are prone to it. The transition from one state of the 

 coat to the other does not take place through any gradation of 

 shade in the general hue, but by i:)atches here and there of the 

 winter colour intermixed with that of summer, giving a pied cov- 

 ering to the animal It appears to be established that 



what ever may be the change which takes place in the structure 



