338 ISLAND LIFE 



PART II 



to show an almost perfect community with the adjacent 

 parts of the continent in its natural productions ; and 

 such is found to be the case. All the higher and more 

 perfectly organised animals are, with but few exceptions, 

 identical with those of France and Germany ; while the 

 few species still considered to be peculiar may be 

 accounted for either by an original local distribution, by 

 preservation here owing to favourable insular conditions, 

 or by slight modifications in adaptation to these conditions 

 resulting in a local race, sub-species, or species. 



Why Britain is Foot in Species. — The former union of 

 our islands with the continent, is not, however, the only 

 recent change they have undergone. There have been 

 partial submergences to the depth of from one hundred to 

 perhaps three hundred feet over a large part of our country ; 

 while during the period of maximum glaciation the whole 

 area north of the Thames was buried in snow and ice. Even 

 the south of England must have suffered the rigour of an 

 almost arctic climate, since Mr. Clement Reid has shown that 

 floating ice brought granite blocks from the Channel Islands 

 to the coast of Sussex. Such conditions must have almost 

 exterminated our preexisting fauna and flora, and it was 

 only during the subsequent union of Britain with the con- 

 tinent that the bulk of existing animals and plants could 

 have entered our islands. We know that just before and 

 during the glacial period we possessed a fauna almost or 

 quite identical with that of adjacent parts of the continent 

 and equally rich in species. The glaciation and sub- 

 mergence destroyed much of this fauna ; and the perman- 

 ent change of climate on the passing away of the glacial 

 conditions appears to have led to the extinction or 

 migration of many species in the adjacent continental 

 areas, where they were succeeded by the assemblage of 

 animals now occupying Central Europe. When England 

 became continental, these entered our country ; but 

 sufficient time does not seem to have elapsed for the 

 migration to have been completed before subsidence again 

 occurred, cutting off the further influx of purely terrestrial 

 animals, and leaving us without the number of species which 

 our favourable climate and varied surface entitle us to. 



