The geographical distribution of animals, with a study of the relations ...

G4 DISTRIBUTION OF ANIMALS. [part i.the antipodes of each other, would be most inconvenient, evenif there were not such difference of opinion about them.Therecan be little doubt, for example, that the most radical zoologicaldivision of the earth is made by separating the Australian regionfrom the rest; but although it is something useful anddefinite to know that a group of animals is peculiar to Australia,it is exceedingly vague and unsatisfactory to say of any othergroup merely that it is extra-Australian. Neither can it be saidthat, from any point of view, these two divisions are of equalimportance. The next great natural division that can be madeis the separation of the Neotropical Region of Mr. Sclater fromthe rest of the world. We thus have three primary divisions,which Professor Huxley seems inclined to consider as oftolerably equal zoological importance. But a consideration ofall the facts, zoological and palseontological, indicates, that thegreat northern division (Arctogsea) is fully as much more importantthan either Australia or South America,as its four componentparts are less important ; and if so, convenience requiresus to adopt the smaller rather than the larger divisions.This question, of comparative importance or equivalence ofvalue, is very difficult to determine.It may be considered fromthe point of view of speciality or isolation, or from that ofrichness and variety of animal forms.In isolation and speciality,determined by what they want as well as what they possess, theAustralian and Neotropical regions are undoubtedly each comparablewith the rest of the earth (Arctogsea). But in richnessand variety of forms, they are both very much inferior, and aremuch more nearly comparable with the separate regions whichcompose it.Taking the families of mammalia as established bythe best authors, and leaving out the Cetacea and the Bats,which are almost universally distributed, and about whoseclassification there is much uncertainty, the number of familiesrepresented in each of Mr. Sclater's regions is as follows :I. Palsearctic region has 31 families of terrestrial mammalia.II. Ethiopian „ „ 40 „ „III. Indian „ „ 31 „ „IV. Australian „ „ 14 „ „V. Neotropical „ „ 26 „ „VI. Nearctic „ ,,23 „ „