54 THE MIGRATION OF BRITISH BIRDS 



south. No purely Polar type could have survived this 

 or any other glacial epoch — not even that one famous 

 Prae-Pliocene ancestor of the Charadriida;. Species, 

 however, that were of South Palaearctic, Ethiopian, 

 Oriental, Australian, Antarctic, South Nearctic, or 

 Neotropical origin survived the vast exterminating in- 

 fluences of the Ice Age, their northern range simply 

 contracting by extermination more or less upon the 

 southern base of those species, or what are now their 

 ancestral forms. Hence the reason why the early 

 Europern flora was a portion of that which now 

 exists only in the tropical and sub-tropical lands of 

 the Eastern Hemisphere. There could have been, 

 therefore, no southern exodus of all living things, as 

 scientists so unanimously assert there was ; no trace 

 whatever of that southern emigration during Pleistocene 

 time exists, and the only species that succeeded in 

 maintaining themselves throughout that era were those 

 whose range was either cosmopolitan throughout the 

 lands whose northern portions were affected, or species 

 whose emigrations had extended from a far southern 

 base, and were then continuous with that base, either 

 by extension of uninterrupted breeding area, by sub- 

 species or representative races, or by migration from 

 and to a southern base, the winter range coalescing 

 with that of summer. One apparent difficulty is pre- 

 sented in the fact of high Arctic animals occurring 

 only in the south during glacial eras, which looks like 

 a purely southern emigration. We have no absolute 

 proof that the southern bases were ever entirely deserted 

 by these what we now class as boreal forms, and I 

 would suggest that these species had endured in the 



