to be a cause exactly adapted to produce the kind and amount of affinity between these distant countries that actually exists.
The Philippine Islands.
A general account of the fauna of these islands, and of their biological relations to the countries which form the subject of this chapter, has been given in my Geographical Distribution of Animals, Vol. I. pp. 345-349; but since the publication of that work considerable additions have been made to their fauna, having the effect of somewhat diminishing their isolation from the other islands. Four genera have been added to the terrestrial mammalia—Crocidura, Felis, Pteromys, and Mus, as well as two additional squirrels; while the black ape (Cynopithecus niger) has been struck out as not inhabiting the Philippines. This brings the true land mammalia to twenty-one species, of which fourteen are peculiar to the islands; but to these we must add no less than thirty-three species of bats of which only ten are peculiar.[[145]] In these estimates the Palawan
group has been omitted as these islands contain so many Bornean species that if included they obscure the special features of the fauna.
Birds.—The late Marquis of Tweeddale made a special study of Philippine birds, and in 1873 published a catalogue in the Transactions of the Zoological Society (Vol. IX. Pt. 2, pp. 125-247). But since that date large collections have been made by Everett, Steere, and other travellers, the result of which has been to more than double the known species, and to render the ornithological fauna an exceedingly rich one. Many of the Malayan genera which were thought to be absent when the first edition of this work was published have since been discovered, among which are Phyllornis, Criniger, Diceum, Prionochilus, and Batrachostomus. But there still remain a large number of highly characteristic Malayan genera whose absence gives a distinctive feature to the Philippine bird fauna. Among these are Tiga and Meiglyptes, genera of woodpeckers; Phænicophaes and Centropus, remarkable cuckoos; the long-tailed paroquets, Palæornis; all the genera of Barbets except Xantholæma; the small but beautiful family Eurylæmidæ; many genera allied to Timalia and Ixos; the mynahs, Gracula; the long-tailed flycatchers, Tchitrea; the fire-backed pheasants, Euplocamus; the argus pheasants, the jungle-fowl, and many others.
The following tabular statement will illustrate the rapid growth of our knowledge of the birds of the Philippines:—
| Land-birds. | Water-birds. | Total. | |
| Lord Tweeddale's Catalogue (1873) | 158 | 60 | 218 |
| Mr. Wardlaw Ramsay's List (1881) | 265 | 75 | 340 |
| Mr. Everett's MSS. List of Additions (1891) | 370 | 102 | 472 |
The number of peculiar species is very large, there being about 300 land and forty-two water birds, which are not
known to occur beyond the group. We have here, still more pronounced than in the case of Borneo, the remarkable fact of the true land birds presenting a larger amount of speciality than the land mammals; for while more than four-fifths of the birds are peculiar, only a little more than half the mammals are so, and if we exclude the bats only two-thirds.
The general character of the fauna of this group of islands is evidently the result of their physical conditions and geological history. The Philippines are almost surrounded by deep sea, but are connected with Borneo by means of two narrow submarine banks, on the northern of which is situated Palawan, and on the southern the Sulu Islands. Two small groups of islands, the Bashees and Babuyanes, have also afforded a partial connection with the continent by way of Formosa. It is evident that the Philippines once formed part of the great Malayan extension of Asia, but that they were separated considerably earlier than Java; and having been since greatly isolated and much broken up by volcanic disturbances, their species have for the most part become modified into distinct local forms, representative species often occurring in the different islands of the group. They have also received a few Chinese types by the route already indicated, and a few Australian forms owing to their proximity to the Moluccas. Their comparative poverty in genera and species of the mammalia is perhaps due to the fact that they have been subjected to a great amount of submersion in recent times, greatly reducing their area and causing the extinction of a considerable portion of their fauna. This is not a mere hypothesis, but is supported by direct evidence; for I am informed by Mr. Everett, who has made extensive explorations in the islands, that almost everywhere are found large tracts of elevated coral-reefs, containing shells similar to those living in the adjacent seas, an indisputable proof of recent elevation.