WHITE RABBITS AND WHITE HARES. 143 



But the cases may be regarded as to some extent the 

 converse of one another ; for, while the red grouse is 

 altogether peculiar to Britain, the blue hare is found in 

 scattered and isolated colonies over a wide extent of 

 Europe and Asia. It turns up again, essentially the 

 same, in the Swiss Alps, in Scandinavia, in Russian 

 Lapland, in Siberia, and in Kamschatka. At present 

 the Alpine and Scotch colonies at least are separated 

 from the central mainguard of the species in the sub- 

 arctic regions by wide intervening seas or plains, across 

 which they are never reinforced by stray fresh arrivals 

 of solitary individuals. The blue hare thus exhibits on 

 the whole the permanence of species under identical 

 conditions, as ^q red grouse and the willow grouse 

 exhibit the tendency towards variability in species where 

 the conditions have become more or less dissimilar. 



We now know pretty accurately how these little 

 isolated colonies got stranded so far apart from one 

 another on the tops of the hillier regions or in the colder 

 parts of the Eurasiatic continent. During the pleistocene 

 period, before and between the recurrent glacial epochs, 

 the ancestors of the blue hare spread over the whole 

 central plain of Europe, which was then cold enough to 

 suit their peculiar tastes ; and their bones, essentially 

 identical with those of the existing individuals, are found 

 in cave deposits of pleistocene date as far south as the 

 Swabian grottos. At that time they ranged over the 

 chilly lowlands of Belgium, Germany, and the North 

 Sea, in company with the reindeer, the arctic fox, the 

 musk sheep, and the lemming, which have now been 

 driven back again to the snow-bound regions of the 

 north ; as well as with the Alpine marmot, the chamois, 



