OF ISLAND FAUNAS 151 



Generally the fauna of islands like the Galapagos, called 

 oceanic by Wallace, is such that its members may 

 be supposed to have been, at least to a large extent, 

 accidentally introduced — ^by storms carrying winged 

 animals out of their usual course, or by mechanical 

 transportation on floating wood, &c. Incidentally we 

 may note that the absence of mammals on oceaoiic 

 islands has often important human consequences, for 

 the paucity of sources of animal food tends to make 

 their human inhabitants cannibals. 



As contrasted with oceanic islands we have the 

 islands which are obviously merely separated portions 

 of the adjacent continent upon whose continental shelf 

 they stand. A good example is furnished by the British 

 Isles, whose fauna is very similar to that of the adjacent 

 continent, but shows impoverishment in several re- 

 spects, apparently as a result of the glacial period. 

 As Ireland was apparently cut off from the continent 

 before Great Britain, and at a stage when many of the 

 animals driven south by the ice had not had time to 

 recover lost ground, we find that its fauna is poorer 

 even than that of the larger island. The following 

 figures, quoted from Wallace, wiU help to render the 

 above statements more precise. Scandinavia possesses 

 about 60 species of mammals, Great Britain 40, and 

 Ireland 22 ; Belgium has 22 species of reptiles and 

 amphibia. Great Britain 13, and Ireland only 4. The 

 question as to the number of pecuHar forms in the 

 British faima has been actively debated. That the 

 red grouse {Lagopus scoticus) of the northern regions is 

 peculiar is generally admitted, though it is nearly aUied 

 to the willow grouse of Scandinavia. We have also 

 some pecuhar fresh-water fish, most of which occur in 

 lakes. The differences are, however, not very striking, 



