ISLAND LIFE. 



[part. r. 



the Alps. There are of course numerous instances in which 

 species occur in two or more islands, or in an island and 

 continent, and are thus rendered discontinuous by the sea, but 

 these involve questions of changes in sea and land which we 

 shall have to consider further on. Other cases are believed 

 to exist of still wider separation of a species, as with the marsh 

 titmice and the reed buntings of Europe and Japan, where 

 similar forms are found in the extreme localities, while a distinct 

 variety, race, or sub-species, inhabits the intervening district. 



Extent and Limitations of Specific Areas, — Leaving for the 

 present these cases of want of continuity in a species, we find 

 the most wide difference between the extent of country occupied, 

 varying in fact from a few square miles to almost the entire 

 land surface of the globe. Among the mammalia, however, 

 the same species seldom inhabits both the old and new worlds, 

 unless they are strictly arctic animals, as the reindeer, elk, and 

 arctic fox, the glutton, the ermine, and some others. The 

 common wolf of Europe and Northern Asia is thought by 

 many naturalists to be identical with the variously coloured 

 wolves of North America extending from the Arctic Ocean to 

 Mexico, in which case this will have perhaps the widest range 

 of any species of mammal. Little doubt exists as to the iden- 

 tity of the brown bears and the beavers of Europe and North 

 America ; but all these species range up to the arctic circle, and 

 there is no example of a mammal universally admitted to be 

 identical yet confined to the temperate zones of the two hemi- 

 spheres. Among the undisputed species of mammalia the 

 leopard has an enormous range, extending all over Africa and 

 South Asia to Borneo and the east of China, and thus having 

 probably the widest range of any known mammal. The winged 

 mammalia have not usually very wide ranges, there being only 

 one bat common to the Old and New Worlds. This is a British 

 species, Vesperugo serotinus, which is found over the larger part 

 of North America, Europe and Asia, as far as Pekin, and even 

 extends into tropical Africa, thus rivalling the leopard and the 

 wolf in the extent of country it occupies. 



Of very restricted ranges there are many examples, but some 

 of these are subject to doubts as to the distinctness of the 



