892 LIFE : OUTLINES OF GENERAL BIOLOGY 



filter for retaining its contents. Strange, too, to reflect that the 

 many Arctic tragedies of starved explorers, and often of Eskimos 

 as well, need never have taken place; and that Nansen on his long 

 drift with the Fram in the ice-pack across the Arctic Ocean was the 

 first guaranteed against failure of normal food-supplies by the 

 simple provision of a few silk plankton-nets, to sink below the ice, 

 and fill with nutritious food from its underlying currents. In all 

 ways, then, have we not increasing evidence for this view of the 

 colder lands and seas as life-encouraging as well as life-selecting? 

 And if so, is not all this a fresh confirmation, from plant and animal 

 life, of the old adage, based mostly on hard individual experience, 

 yet sometimes social experience too — "Sweet are the uses of 

 adversity!"? 



VANISHED BRITISH ANIMALS— Not very long ago, geologically 

 speaking, there was no North Sea, and Britain was an outlier 

 of the Continent. It had then, as we have said, its share of the 

 continental mammals; for there are British remains of the mam- 

 moth, the cave-bear, the sabre-toothed tiger, the cave-lion, the 

 woolly rhinoceros, and so on. Gradually, glaciers were formed, and 

 the Ice Ages set in. These were ages of severe sifting, and there were 

 four of them, with three intervening milder spells, during which 

 some of the big animals that had been exterminated in Britain came 

 back again from Southern Europe. But most of Britain, except a 

 strip in the south of England, was thickly covered with ice-sheets, 

 and the result was that almost all the mammals disappeared. Men 

 of some sort were living in North Europe in the later Ice Ages, but 

 remains of the "modern man type", our own Homo sapiens species, 

 are all post-glacial. 



The second chapter in the story was the amelioration of the cli- 

 mate, the melting of the ice, and the re-colonising of Britain from 

 the Continent. Most of the giants had disappeared from Europe, so 

 they could not be reinstated in Britain; but some stately creatures 

 shared in the re-colonisation, such as the reindeer and the magnifi- 

 cent giant-deer, usually called the "Irish elk". There were also wild 

 cattle and wild boars, wolves and bears, besides some smaller mam- 

 mals such as beavers and lemming. All these have since been lost ; 

 unless we reckon the domestic pig as the descendant of the wild 

 boar. This re-colonisation also included all the diverse wild mammals 

 we now have, though some of these may have lingered in the non- 

 glaciated parts of what is now the south of England. 



The third chapter was the shutting of the door. By regional 

 changes in the level of the earth's crust. Great Britain became an 

 island. Ireland also became independent, and its connection with 

 Great Britain was deeply severed before the sister isle had received 

 its full share of the mammals that had been re-established in 



