If these considerations are well founded, the objections of those who study insects or molluscs, for example,--that our regions are not true for their departments of nature--cannot be {58}maintained. For they will find, that a careful consideration of the exceptional means of dispersal and conditions of existence of each group, will explain most of the divergences from the normal distribution of higher animals. We shall thus be led to an intelligent comprehension of the phenomena of distribution in all groups, which would not be the case if every specialist formed regions for his own particular study. In many cases we should find that no satisfactory division of the earth could be made to correspond with the distribution even of an entire class; but we should have the coleopterist and the lepidopterist each with his own Geography. And even this would probably not suffice, for it is very doubtful if the detailed distribution of the Longicornes, so closely dependent on woody vegetation, could be made to agree with that of the Staphylinidæ or the Carabidæ which abound in many of the most barren regions, or with that of the Scarabeidæ, largely dependent on the presence of herbivorous mammalia. And when each of these enquirers had settled a division of the earth into "regions" which exhibited with tolerable accuracy the phenomena of distribution of his own group, we should have gained nothing whatever but a very complex mode of exhibiting the bare facts of distribution. We should then have to begin to work out the causes of the divergence of one group from another in this respect; but as each worker would refer to his own set of regions as the type, the whole subject would become involved in inextricable confusion. These considerations seem to make it imperative that one set of "regions" should be established as typical for Zoology; and it is hoped the reasons here advanced will satisfy most naturalists that these regions can be best determined, in the first place, by a study of the distribution of the mammalia, supplemented in doubtful cases by that of the other vertebrates. We will now proceed to a discussion of what these regions are. _Various Zoological Regions proposed since 1857._--It has already been pointed out that a very large number of birds are limited by the same kind of barriers as mammalia; it will therefore not be surprising that a system of regions formed to suit the {59}one, should very nearly represent the distribution of the other. Mr. Sclater's regions are as follows:-- 1. The Palæarctic Region; including Europe, Temperate Asia, and N. Africa to the Atlas mountains. 2. The Ethiopian Region; Africa south of the Atlas, Madagascar, and the Mascarene Islands, with Southern Arabia. 3. The Indian Region; including India south of the Himalayas, to South China, and to Borneo and Java. 4. The Australian Region; including Celebes and Lombock, eastward to Australia and the Pacific Islands.