There are certain facts in the distribution of animals which are commonplaces of knowledge, but which may be set forth with definiteness. Everybody knows that an animal has a given range: Elephants, for example, are found in India and certain adjacent parts of Asia, and again in Africa; the Rhinoceroses have roughly the same range; the Tiger is limited to Asia; the {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 _Solenodon_ 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 is 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 only 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 intermediate tracts.