THE NEW EVOLUTION 



These Cambrian creatures could not have withstood 

 the pounding of the surf along the shores of the pres- 

 ent oceans. Absence of a surf line means absence of 

 strong winds, or frequent violent storms, which fur- 

 ther suggests a blanket of clouds resulting in more or 

 less uniform temperatures over the greater part, or 

 possibly all, of the earth's surface. 



Speaking in less general terms, we learn from the 

 rocks that in the palaeozoic era coral reefs extended 

 into high latitudes. The luxurious and uniform 

 development of cryptogams over the earth during 

 Carboniferous time indicates a warm moist climate 

 which varied but little with latitude. In the Pleis- 

 tocene or Ice Age the remains of reindeer, lem- 

 ming, musk-oxen and other Arctic animals in central 

 Europe show clearly that at that time the climate of 

 central Europe was much colder than it is now. 



In other words, climatic changes have been con- 

 stantly going on. The present distribution of heat 

 and cold, of dampness and of dryness, is but a passing 

 phase in the history of the earth's surface. 



All of the changes which take place in any region 

 naturally affect all the animal inhabitants of that 

 region. Some may die out and be replaced by others 

 from another region, some may assume a more or less 

 widely different guise, and some may be able to exist 

 unchanged under the new conditions. 



But changes in climatic conditions however severe 

 do not affect the basic requirements of food, water 

 and air, which are always present, at least up to the 

 point of complete desiccation or of permanent frost. 



