INTRODUCTION TO SOCIOLOGY 241
The northern region, whose limit is not far south of the isothermal zero line, has its peculiar mammifers the polar fox, the reindeer, and the white bear. The country of the bear is less extensive than that of the fox ; that of the fox, less than that of the reindeer; the latter reaches to the interior of the northern forests, where the polar fox does not penetrate.
The region of middle Europe is bounded on the north by the frontier of the reindeer; on the west, by the ocean; on the south, by the Pyrenees, the Cevennes, the Alps, the Balkans, and the Caucasus ; east of the Ural, as we have said, there is only an imperfect frontier between Europe and Asia. Asia and the vast plains to the southwest of Siberia continue from the steppes of European Russia.
The Mediterranean slope, so remarkable for its multiform geographic structure, is equally remarkable for the great number of small regions each having its peculiar animals. Is it not also remarkable that in the archipelago, in Greece, in Sicily, in Italy, in the Island of Sardinia, in the south of Gaul, in the retreats in the midst of mountains, so difficult to cross for man as well as for other mammifers, are settled a crowd of little local civili- zations, municipal districts, whose influence is felt even today ? In regard to mammifers, Australia is totally different from South America and Africa.
Dr. Richardson has ascertained the existence of a large kingdom of maritime fauna in the Pacific Ocean, occupying a zone of 42 north and south of the equator. This kingdom comprises the whole of those waters which border Australia, New Zealand, the Malay archipelago, China, and Japan. Its population consists of almost the same varieties. At the frontier of this vast region appear other varieties peculiar to polar countries and which are confounded in certain points with the tropical species. This maritime realm is not without analogy with the great terrestrial domain which it borders. They are equally enormous in their area and their population. It is necessary also to keep in mind this mixture of varieties operat- ing at the frontiers in general, of the several zones of fauna, and which corresponds to an analogous phenomenon in the frontier zones of political societies.
