UI BARRIERS TO DISTRIBUTION 79 
Jaguar to America, and so forth. The entire expanse of country 
which is inhabited by an animal is called its area of distribution. 
Such areas are larger or smaller. The Lion ranges over the whole 
of Africa, a small part of India, and some neighbouring countries ; 
on the other hand, the Insectivore So/enodon is limited to Cuba 
and Hayti, a separate species to each. Among other groups of 
animals are instances of an even more restricted range. There 
are humming-birds confined to the slopes of a single mountain, 
and fishes limited in their range to a single small lake. 
A species may be found everywhere within the area of its 
distribution, or it may be confined to a number of limited tracts 
within that area. In this case it 1s usual to speak of “ stations.” 
In such cases the species in question is generally suited to some 
particular kind of environment. Thus the Otter and other 
aquatic mammals will only be found where there is water; and 
intervening tracts of waterless country will contain no Otters. 
Goats and Chamois live gnly upon mountains; the intervening 
plains are destitute of them. This discontinuity of distribution 
within the area is very general. But a discontinuity of area is 
also seen—not so commonly however; and, indeed, when it does 
occur, it is a matter of a genus and not of a species. Thus the 
Tapir is found in the East Indies on the one hand and in South 
and Central America on the other, being absent in the inter- 
mediate tracts. 
It is clear that tracts of country eminently suitable for the 
housing of a particular mammal do not always possess that kind, 
or even an allied form. Africa, for example, possesses no arboreal 
Anteaters; there are no Anteaters at all (of the order Edentata) 
in Australia, though there are plenty of ants for them to feed upon, 
and tropical conditions of climate prevail. But as in these cases 
the inference may be denied on the grounds that no experiments 
exist to prove or to disprove the assertion, the matter may be 
better emphasised by such cases as the introduction of the Rabbit 
into Australia, and various mammals, such as Goats, into oceanic 
islands. The plague caused by the former is a matter of notoriety. 
But although climate and conditions and animal inhabitants do 
not march accurately together, there is certainly some connexion 
between temperature and the range of animals. Mr. Lydekker 
writes on this point as follows: “The llama-like animals, re- 
spectively known as vicunas and guanacos, are met with in 
