138 COLIN CLOUT'S CALENDAR. 



species ranged over the whole central belt of Europe 

 corresponds roughly with the age of the palaeolithic 

 cave-men ; with the post-glacial neolithic or prehistoric 

 age we find a gradual and continuous retreat northward 

 of the animals adapted to colder habitats. In the earlier 

 neolithic days the moose and the reindeer were still 

 found as far south as Yorkshire ; by the dawn of the 

 historical period they were extinct in England, though 

 the Scandinavian jarls of Orkney still hunted reindeer 

 among the straths of Caithness as late as the middle of 

 the twelfth century. During the first period, too, both 

 the blue hare and the common hare ranged together over 

 the plains of England ; but as time went on and the 

 climate became milder the northern species retreated to 

 the Scotch hills, where it found a more congenial atmos- 

 phere, leaving the southern plains and valleys entirely to 

 the occupation of its ruddy ally. In the same way the 

 blue hares of Germany also became extinct ; and so the 

 species was reduced to three isolated groups one in 

 Scotland, one in Switzerland, and one large connected 

 body in northern Europe and Siberia. Here for the 

 most part the conditions remained so similar that the 

 various animals underwent no material differentiation : 

 though they vary slightly from place to place in the de- 

 gree to which they retain the habit of turning white in 

 winter. 



In those countries where the snow lies long on the 

 ground they keep up the change of coat as a protection 

 against their enemies, natural selection effectually cutting 

 off any specimen which varies toward brown or black at 

 that season ; and here the stoats also for the most part 

 assume the white ermine dress in winter, so as to come 

 upon them unawares. The black tips to the ears doubt- 

 less serve to guide the leverets in following their dams 



