196 MUSTELAM. 



The winter change of colour which this species so 

 universally assumes in northern climates, is not only 

 matter of much interest to the naturalist and the phy- 

 siologist, but, as we shall presently see, of considerable 

 importance also in a commercial point of view. The 

 whole of the coloured parts of the fur become of the 

 purest white, excepting the extremity of the tail, which 

 remains permanently black ; and the under parts retain 

 a slight yellowish tinge. This is effected, not by the 

 loss of the summer coat and the substitution of a new 

 one for the winter, but by the actual change of colour 

 in the existing fur. It is not easy to offer a satis- 

 factory theory for this phenomenon, but we may per- 

 haps conclude that it arises from a similar cause to that 

 which produces the grey 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. This 

 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 patches here and there of the winter 

 colour intermixed with that of the summer, giving a pied 

 covering to the animal. 



In northern latitudes, even in the alpine districts of 

 Scotland, this change is universal ; but farther south it 

 becomes an occasional, and even rare, occurrence. In 

 Northumberland, Durham, and other counties in the 

 north of England, it is very frequent, although far 

 from general ; in Lincolnshire, Cambridgeshire, and the 

 Midland Counties generally, it is sometimes seen ; and 

 there are two specimens of the Ermine in the Museum 



