32 
ISLAND LIFE. 
[part t. 
of distribution occupies a large portion of Europe. There are, 
indeed, a few species limited to Central or Western or Southern 
Europe, and these are almost the only cases in which we can 
use the word for zoological purposes without having to add to 
it some portion of another continent. Still less useful is the 
term Asia for this purpose, since there is probably no single 
animal or group confined to Asia which is not also more or less 
nearly confined to the tropical or the temperate portion of it. 
The only exception is perhaps the tiger, which may really be 
called an Asiatic animal, as it occupies nearly two-thirds of the 
continent; but this is an unique example, while the cases in 
which Asiatic animals and groups are strictly limited to a 
portion of Asia, or extend also into Europe or into Africa or to 
the Malay Islands, are exceedingly numerous. So, in Africa, 
very few groups of animals range over the whole of it without 
going beyond either into Europe or Asia Minor or Arabia, 
while those which are purely African are generally confined to 
the portion south, of the tropic of Cancer. Australia and 
America are terms which better serve the purpose of the 
zoologist. The former defines the limit of many important 
groups of animals; and the same may be said of the latter, 
but the division into North and South America introduces 
difficulties, for almost all the groups especially characteristic of 
South America are found also beyond the isthmus of Panama, 
in what is geographically part of the northern continent. 
It being thus clear that the old and popular divisions of the 
globe are very inconvenient when used to describe the range of 
animals, we are naturally led to ask whether any other division 
can be made which will be more useful, and will serve to group 
together a considerable number of the facts we have to deal with. 
Such a division was made by Mr. P. L. Sclater more than 
twenty years ago, and it has, with some slight modifications, 
come into pretty general use in this country, and to some extent 
also on the continent ; we shall therefore proceed to explain its 
nature and the principles on which it is established, as it will 
have to be often referred to in future chapters of this work, 
and will take the place of the old geographical divisions whose 
extreme inconvenience has already been pointed out. The 
