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 Lombok, Eastward to Australia and the Pacific islands.
5.—The Nearctic Region, including Greenland, and North America, to Northern Mexico.
6.—The Neotropical Region, including South America, the Antilles, and Southern Mexico.
This arrangement is based upon a detailed examination of the chief genera and families of birds, and also very nearly represents the distribution of mammals and of reptiles. Its regions are not, as in other subsequently proposed and more artificial systems, controlled by climate; for they range, in some instances, from the pole to the tropics. It probably approaches more nearly than any other yet proposed to that desideratum, a division of the earth into regions, founded on a collation of the groups of forms indigenous to or typical of them, and upon a selection of those peculiar to them; with a disregard of, or only admitting with caution, any which, though common to and apparently establishing connection between two or more regions, may have in fact but little value for the purpose of such comparison; from the fact of its being possible to account for their extended range by their capability of easy transport from one region to another by common natural agencies.[41]
Such an arrangement should be consistent with the retrospective information afforded by palæontology; and, taking an extended view of the subject, be not merely a catalogue of the present, but also an index of the past. It should afford an illustration of an existing phase of the distribution of animal life, considered as the last of a long series of similar phases which have successively resulted from changes in the disposition of land and water, and from other controlling agencies, throughout all time. A reconstruction of the areas respectively occupied by the sea and the land at different geological periods will be possible, or at least greatly facilitated, when a complete system of similar groupings, illustrative of each successive period, has been compiled.
It is obvious that any great cosmical change, affecting to a wide extent any of the regions, might determine a destruction of specific existence; and this on a large scale, in comparison with the change which is always progressing in a smaller degree in the different and isolated divisions.
The brief remarks which I have made on this subject are intended to suggest, rather than to demonstrate—which could only be done by a lengthy series of examples—the causes influencing specific existence and its in many cases extreme frailty of tenure. And I shall now conclude by citing from the works of Lyell and Wallace a short list of notable species, now extinct, whose remains have been collected from late Tertiary, and Post Tertiary deposits—that is to say, at a time subsequent to the appearance of man. From other authors I have extracted an enumeration of species which have become locally or entirely extinct within the historic period.
These instances will, I think, be sufficient to show that, as similar destructive causes must have been in action during pre-historic times, it is probable that, besides those remarkable animals of which remains have been discovered, many others which then existed may have perished without leaving any trace of their existence. There is, consequently, a possibility that some at least of the so-called myths respecting extraordinary creatures, hitherto considered fabulous, may merely be distorted accounts—traditions—of species as yet unrecognised by Science, which have actually existed, and that not remotely, as man’s congener.