WHITE RABBITS AND WHITE HAKES. 139 



across the snow, without being so conspicuous as to 

 betray the animal to its enemies from a little distance. 

 On the other hand, in northern Siberia, where snow lies 

 almost all the year round, the blue hare has a perma- 

 nently white coat ; but in southern Russia it hardly 

 alters in hue, except on the back and sides. 



The Irish hare is regarded by competent authorities as 

 a variety of the blue hare, produced under the excep- 

 tionally favorable circumstances of a very warm insular 

 habitat, combined with freedom from competition. In 

 America the closely similar species locally called the 

 rabbit accommodates itself in much the same way to 

 the different zones of climate being white in winter in 

 the north, and yellowish-brown all the year round in the 

 middle and southern States. In this case the two varie- 

 ties mix so much in the uninterrupted land-surface 

 between the Arctic regions and the Gulf of Mexico that 

 they could not readily grow into distinct species. Bat 

 in the case of the red grouse of Britain 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 tem- 

 perate 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 color 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 conditions. 



