6 INFLUENCE OF CLIMATIC AND GEOLOGICAL CHANGES 



would have been southward in Britain, and could only have 

 carried them in that direction. Wading and swimming birds, 

 which commonly come to Britain from the north and from the 

 east in autumn, leaving the colder districts at a time when the 

 seeds are ripe, would be the means of bringing the smaller ones 

 to this country. 



In a comparison of the plants of this country with those of the 

 Continent it is clear that both were conterminous at the time of 

 distribution. Those species which have a northern tendency 

 with us, have the same on the Continent. The characteristic 

 plants of our mountains and high summits grow on similar 

 altitudes on the Continent. On the other hand the delicate 

 plants of the south-west approach us from France and the 

 Spanish Peninsula. Mr. J. G. Baker points out that in studying 

 the distribution of our flora, it was accomplished before the 

 land and sea acquired their present relations, and considering 

 how long a time has elapsed since Great Britain has been 

 separated from the Continent, and the absence of endemic 

 types from its flora, it is a strong argument against the idea 

 of a rapid spontaneous differentiation of specific types in 

 plants. 



The submersion which was supposed to have occurred during 

 the latter part of the Glacial Age affected the greater portion of 

 the British Isles, and when they became Continental the old 

 fauna was succeeded by a migration from the Continent ; 

 sufficient time, however, had not elapsed to complete it before 

 another subsidence, which cut off the further influx of purely 

 terrestrial animals and plants, leaving us without the number 

 of species which our variable climate and varied surface would 

 lead us to expect. To this cause must our comparative poverty 

 in mammalia and reptiles be ascribed. Germany possesses 

 nearly ninety species of land mammalia, Scandinavia about sixty, 

 while Britain has only about forty, and Ireland twenty-two ; as 

 the depth of the Irish Sea is somewhat greater than the German 

 Ocean, the connecting land would have a shorter time for their 

 migration. This has been the cause of the comparative 



