184 HISTORY OF THE EUROPEAN FAUNA. 



with Scotland, and the latter with Ireland (Fig. 6, 

 p. 126). There is no doubt that the food-supply in the 

 Arctic Regions was decreasing with an increase of 

 snowfall and with the gradual lowering of the land, 

 which reduced also the habitable area. Arctic species 

 therefore were driven south in search of fresh pastures. 

 But it need not be supposed that anything like a vast 

 destruction of the fauna of the Arctic Regions took 

 place. Only fewer mammals were able to find food 

 in a given space than heretofore. This southward 

 migration may have commenced, in the case of 

 plants and the invertebrates, at a much earlier time, 

 during the Miocene or Pliocene Epochs, but it 

 is doubtful whether the mammals and birds which 

 we find in our pleistocene and recent deposits 

 began to travel south much before the commence- 

 ment of the Glacial period. The beginning of the 

 Glacial period in England, I think, is indicated by 

 the deposition of the Red Crag, though the latter is 

 generally regarded as belonging to the pliocene 

 series. Much of the northward migration from 

 the British Islands of Lusitanian and other forms 

 had then ceased, but we have in Scandinavia, just 

 as in these islands, a southern relict fauna and flora, 

 plants and animals which had wandered across what 

 is now the German Ocean from Scotland to Scan- 

 dinavia, and have never become extinct in that 

 country to the present day. I need only mention 

 the Red Deer, the Badger, and Slugs of the genus 

 A rion. 



