JUNE 125 



owning common descent from a primitive marsupial 

 ancestry. Anyhow the creature reported on by Owen 

 lived in an age when the London clay was being formed 

 and the climate of England was tropical. Any small 

 mammal which existed in that world would have to 

 pick its way among the feet of such monsters as 

 Palseotherium and Dinoceras, not to mention such less 

 bulky associates as tapirs and four-toed horses. Altered 

 conditions of land and climate swept most of these 

 mighty types from the face of the earth; but the 

 humble insectivores underwent little change. The 

 mole sought safety by adopting a subterranean life; 

 the hedgehog remained above ground and developed 

 defensive spines; both devices proved perfectly satis- 

 factory, so that, arriving at Pliocene times, when the 

 English crag was formed, we find remains of hedgehogs 

 indistinguishable from those of the present day. They 

 had as companions various kinds of pachyderms — 

 elephants, mastodon, hippopotamus, rhinoceros, besides 

 the formidable sabre-toothed lion and our contempo- 

 rary beavers and otters. 



But these mighty forms of life were doomed to ex- 

 tinction. The climate slowly but steadily grew colder ; 

 by the time the English crag and forest beds had been 

 formed it had become of arctic severity, and the greater 

 part of what is now the British Isles was cased in a 

 mantle of ice some hundreds of feet thick. Over the 

 whole of Northern Europe every recognisable form of 

 life, animal and vegetable, was extinguished. Thousands 

 of years had to pass — thousands of feet of solid rock 

 had to be ground into glacial clay — the land had to be 



