EXTERMINATION IN ANIMAL LIFE. 285 



present day, and in our own climate, by observing the deadly 

 operation of one night's extra and unusual severity of frost on 

 much plant life, or the avian destruction during an exceptionally 

 severe winter. Even in present sunny Italy periods of nipping 

 cold have taken place ; for, as Gilbert White argued : " Surely 

 the judicious Virgil, when writing a didactic poem for the region 

 of Italy, could never think of describing freezing rivers, unless 

 such severity of weather pretty frequently occurred."* Mr. 

 Dixon has somewhat recently expressed his opinion that the 

 conditions of the Ice Age, instead of being grand incentives to 

 southern migration, exerted a vast exterminating influence, and 

 that they must have caused the utter extinction of every species 

 whose breeding range was entirely confined to the areas glaci- 

 ated, or sufficiently within the influence of glaciation to render 

 existence impossible. The effects of the Glacial Epoch on the 

 dominant Euro- Asian fauna are shown to be exterminating 

 rather than incentive to southern migration. f The same 

 opinion has been expressed by Mr. Emery in studying the 

 distribution of Ants: "Later the Glacial Epoch destroyed in 

 Europe nearly all the rest of tropical insects, their return being 

 made impossible by the natural barriers of sea, deserts, and 

 mountains accumulated southward and eastward of our con- 

 tinent."! Sir Charles Lyell, in remarking on the absence of 

 organic remains in stratified drift of the glacial period, regards 

 the possibility of their having been originally scarce, and not 

 simply destroyed by time, rain-water, and other agencies, for, as 

 he writes, "we read of the water of the sea being so freshened 

 and chilled by the melting of icebergs in some Norwegian and 

 Icelandic fiords, that the fish are drawn away, and all the 

 mollusca killed." § 



We have many records of the baneful effect of sudden and 

 severe cold on birds. The Eev. J. C. Atkinson, writing in 1891, 

 relates that on a Whit-Monday some thirty years previously 

 three inches of snow fell, and there were two nights — those 



* • Nat. Hist. Selborne,' Harting's edit., p. 151. 

 f ' The Migration of British Birds,' p. 287. 



I " On the Origin of European and North American Ants," ' Nature,' 

 vol. lii. p. 399. 



§ ' The Antiquity of Man,' 4th edit. p. 296. 



