146 COLIN CLOUTS CALENDAR. 



and the willow grouse of Scandinavia such a change has 

 been facilitated by absence of interbreeding ; and in the 

 case of the Irish hare we get a similar change, now 

 actually in course of operation. There is reason to 

 believe that in America a glacial species has spread over 

 the whole country, for even the southern forms undergo 

 a slight winter change of coat : whereas in Europe the 

 return of an exiled temperate species after the retreat of 

 the ice has driven the glacial kind steadily northward, 

 or isolated it among the colder heights of Scotland and 

 Switzerland. It is worthy of observation that where the 

 hares change colour in winter the stoats also usually 

 assume their ermine dress, but where the hares remain 

 of one hue throughout the year the stoats for the most 

 part follow suit under the influence of identical con- 

 ditions. 



