ii4 Animal Life and Intelligence. 



competition for means of subsistence in these areas must 

 have been rendered extremely severe. Elimination was at 

 a maximum. Then followed the withdrawal of glacial 

 conditions. The increasing geniality of the climate allowed 

 an expansion of life within a given area, and the with- 

 drawal of snow and ice further and further north set free 

 new areas into which this expanding life could migrate 

 and find subsistence. The hard times of the glacial period 

 were succeeded by good times of returning warmth and an 

 expanding area ; and if, as some geologists believe, there 

 was an inter-glacial period (or more than one such period) 

 in the midst of the Great Ice Age, then hard times and 

 good times alternated during the glacial epoch. 



Expansion and contraction of life-areas have also been 

 effected again and again in the course of geological history 

 by elevations and subsidences of the land. At the beginning 

 of Mesozoic times much of Europe was dry land. In 

 Triassic and Bhsetic times there were lakes in England and 

 in Germany, and a warm Mediterranean Sea to the south. 

 Subsidence of the European area brought with it a lessened 

 land-area and an increased sea-area : bad times and in- 

 creased competition for land animals ; good times and 

 a widening life-area for marine forms of life. This con- 

 tinued, with minor variations, till its culmination in the 

 Cretaceous period. Then came the converse process : the 

 land-areas increased, the sea was driven back. A good 

 time had come for terrestrial life ; the marine inhabitants 

 of estuaries and inland seas felt the pressure of increased 

 competition in a lessening area. And so there emerged 

 the continental Europe of the beginning of the Kainozoic 

 era. And it is scarcely necessary to remind those who 

 are in any degree conversant with geology that during 

 tertiary times there have been alternate expansions and 

 contractions of life-areas, marine and terrestrial, the former 

 bringing good times, the latter hard times and a heightened 

 struggle for existence. 



Now, what would be the result of this alternation of 

 good times and hard times ? During good times varieties, 



