RANGE BASE OR REFUGE AREAS 55 



south during milder intervals of climate, by portions 

 of them ascending to great altitudes on mountains as 

 migrants, which again descended to the lowlands as 

 residents as the climate again became glacial. Southern 

 mountains were in fact the grand preservers of the 

 species in the south during warm intervals of climate, 

 just as we find to be the case to-day. It is by this 

 means probably many types or species have succeeded 

 in maintaining their existence during the Glacial Epoch; 

 many instances might be given of boreal birds breeding 

 at high elevations on southern mountain ranges, and 

 wintering on the lowlands, or migrating much further 

 south to an original base. The migratory tendencies 

 of all Arctic animals is significant. These animals 

 are Arctic in the sense of having become Arctic since 

 the Glacial Epoch passed away. There is no evidence 

 whatever to suggest that they were confined exclu- 

 sively to the Polar latitudes during Pre-Glacial time. 

 Arctic animals are species that have spread north 

 from southern bases during Post-Glacial time, not 

 species that have been driven from a previous Polar 

 haunt by glacial climates. They are species that have 

 slowly adapted themselves to Arctic conditions, as 

 their range has been extended north by Post-Glacial 

 emigration into Polar latitudes. Note the various 

 Arctic forms or representative races of more southern 

 species. Arctic climates would produce Arctic forms. 

 This by no means implies that Arctic species emigrated 

 south, but that a glacial epoch exterminated them, 

 and that the effect of a much lower latitudinal Arctic 

 climate prevailing during glacial epochs had its usual 

 effect on species, or such portion of species that came 



