u 
ISLAND LIFE. 
[part. I. 
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 
