162 HISTORY OF THE EUROPEAN FAUNA. 



an extremely slight admixture of American or 

 Asiatic types, again points to a former more 

 intimate connection between North America and 

 Arctic Europe, and indeed he remarks (p. 252), 

 " It is inconceivable to me that so many Scan- 

 dinavian plants should, under existing conditions 

 of sea, land, and temperature, have not only found 

 their way to Greenland by migration across the 

 Atlantic, but should have stopped short on its 

 western coast and not crossed to America." 



Hooker's view, that the Scandinavian flora is of 

 great antiquity, that, at the advent of the Glacial 

 period, it was everywhere driven southwards, and 

 that during the succeeding warm epoch the sur- 

 viving species returned north, has been adopted by 

 the great majority of naturalists. 



The natural corollary of this 'theory is that there 

 must have been, between the beginning of the Glacial 

 period and the present time, either two independent 

 land-connections between the Polar Regions and 

 Northern Europe at different epochs to enable 

 animals and plants to travel southwards and once 

 more to regain their former northern home, or, 

 that during the whole of the Glacial period the 

 Polar Regions were uninterruptedly connected with 

 Northern Europe, until the fauna and flora had once 

 more reached their northern goal, after the Polar 

 lands had been desolated by the supposed rigours of 

 that period. 



In following the history of the Arctic migration to 



