60 MOSTLY MAMMALS 



It was doubtless assumed that, had the experiment been 

 extended over a longer period, the white would have 

 gradually extended downwards till the whole hair became 

 blanched. But had this been the normal way in which 

 the change from a black to a white coat is brought about, 

 it is obvious that animals ought frequently to be captured 

 in which the coat is in the same condition as that of the 

 lemming. So far, however, as I am aware, no such con- 

 dition has ever been described. 



Moreover, it is perfectly well known that, apart from 

 those which turn white in winter, a large number of 

 animals have a winter coat differing markedly in colour, 

 as well as in length, from the summer dress. The roebuck, 

 for instance, is of a brilliant foxy red in summer, while in 

 winter it is grey- fawn with a large patch of pure white on 

 the buttocks. And it is quite clear that the change from 

 red to grey, and the development of the white rump-patch, 

 is due to the shedding of the short summer coat and its 

 replacement by the longer winter dress. Obviously, there- 

 fore, it is natural to expect that a similar change of coat 

 takes place in the case of mammals which turn white in 

 winter. 



That the change in spring from a white to a dark dress 

 is due to a shedding of the fur seems to be admitted on 

 all hands, for it would obviously be quite impossible for 

 long hairs to become short, or for white ones to turn 

 brown. And even in animals which do not alter their 

 colour in any very marked degree according to season, the 

 spring change of coat is sufficiently obvious. For the 

 winter coat, owing to the long time it is carried and the 

 inclemency of the season when it is in use, becomes much 

 faded and worn by the time spring comes, and the con- 

 trast between it and the fresh and brilliant summer coat 



