CHAPTEE IV. 



THE FAUNA OF ISLANDS. 



The principles dealt with in the preceding Chapter 

 are also admirably illustrated by the fauna of islands, of 

 which some account will now be given. 



The Fauna of the British Isles. 



The islands of Great Britain and Ireland are situated 

 upon a bank which conies so near the surface that the sea 

 is nowhere more than comparatively a few fathoms deep. 

 From the neighbouring coast of France England is se- 

 parated by barely thirty miles. There can be no doubt 

 in fact that the separation is, geologically speaking, very 

 recent, probably within the period of human occupation. 

 We should expect therefore to find the very closest 

 similarity in the fauna of England of the adjacent parts 

 of the Continent; this is precisely what we do find, the 

 differences being chiefly in the poverty of the British 

 fauna as compared with that of the Continent. 



As Mr Wallace has pointed out, this poverty is 

 probably to be accounted for by the recent glaciation of 



