RANGE BASE OR REFUGE AREAS 27 



inevitable result of such changes has been on the one 

 hand to contract the range of species far to the south 

 by extermination, on the other hand to encourage 

 northern emigration, both movements being on a scale 

 so enormous that we can only form a conception of 

 their magnitude by a close and careful study of their 

 results as manifested by the present distribution of 

 existing species. What became of the numerous forms 

 of animal and vegetable life dwelling in the areas 

 suffering such glacial visitation ? whence did the}' go 

 during the devastation of their northern or alpine homes 

 by the invading ice-sheets, snow-fields, and glaciers ? 

 Before we can hope to understand the philosophj- of 

 their distribution at the present time it becomes abso- 

 lutely necessary for us to endeavour to trace out the 

 areas these species occupied during the era of their 

 extermination from glaciated areas, and from which 

 they again set out as colonists upon the gradual return 

 of more favourable climatal conditions. 



Taking as our guide the present geographical dis- 

 tribution of the European fauna and flora we shall, I 

 think, experience little difficulty not only in tracing out 

 these areas of refuge, but in ascertaining to some extent 

 the physical changes which those areas have undergone 

 during late Pliocene and Post-Tertiary time. So far 

 as Europe is concerned, the evidence I have been able 

 to collect points to the existence of no less than three 

 fairly well defined range bases or refuge areas. Europe, 

 the western coast-line of which, following the contour of 

 100 fathoms, then extended outside the British area, at 

 the climax of the Ice Age was to a great extent covered 

 by one vast ice-sheet which descended to about lat. 50' 



