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Show 360 ISLAND LIFE. (PART H. · of birds and mammals may have been driven south-swpeacrd le, s an d rang ed over suitable portions of the whole are. a. J then separated by subsidence, and these specws ava was . h · · t f became imprisoned there; while those m t e remammg par o · the Malayan area again migrated northward when .the cold had passe d a Way from their former home, the eq.u atonal forests· 11o f Borneo, Sumatra, and the Malay Peninsul~ be~ng more espec1a y adapted to the typical Malayan fauna whwh 1~ there developed in rich profusion. A little later the subs1dence may h~ve extended farther north, isolating Borneo and Sumatra, but probably leaving the Malay Peninsula as a ridge betw~en them as far as the islands of Banca and Biliton. Other shght changes of climate followed, when a further subsidence separated these last-named islands from the Malay Peninsula, and left them with two or three species which have si~ce become sli%htl.y modified. We may thus explain how it 1s that. a spec~es 1s sometimes common to Sumatra and Borneo, wlule the mterveninO' island (Banca) possesses a distinct form.1 In ~y Geo,qraphical Dist1·ib~dion of Animals, Vol. I.,_p. 357, I have given a somewhat different hypothetical explanatwn of tll(~ relations of Java and Borneo to the continent, in which I took account of changes of land and sea only; but a fuller consideration of the influence of changes of climate on the migration of animals, has led me··to the much simpler, and, I think, more probable, explanation above given. The amount of the rclationshi p between Java and Siam, as well as of that between Java and the Himalayas, is too small to be well accounted for by an independent geographical connection in which Borneo and Sumatra did not take part. It is, at the same time, too distinct and indisputable to be ignored; and a change of climate which should drive a portion of the Himalayan fauna southward, leaving a few species in Java, from which they could not return owing to its subsequent isolation by subsidence, seems to be a cause exactly adapted to produce the kind and amount of affinity between these distant countries that actually exists. 1 Pitta megarhynchus (Banca) allied to P. br·uchyurus (Borneo, Sumatra, Malacca); and Pitta banglcanus (Banca) allied to P. sordidus (Borneo and Sumatra). CIIAP. XVH.] THE PHILIPPINES. 3Gl The Philippine Islands.-A sufficiently detailed account of the fauna of these islands, and their relation to the countries which form the subject of this chapter, has been given in my Geographical Distr'ib~ttion of Animals., Vol. I. pp. 345-349; but since that time considerable additions have been made to their fauna, and these have had the effect of diminishing their isolation from the other islands. Six genera have been added to the terrestrial mammalia-Crocidura, Felis, Tragulus, Hystrix, 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 known mammalia to twenty-one species, and no doubt several others remain to be discovered. The birds have been increased from 219 to 288 species, and the additions include many Malayan genera which were thought to be absent. Such are I hyllornis (green bulbuls); Eurylremus (gaper), Malacopteron, one of the babblers; and Criniger, one of the fruitthrushes; as well as Batrachostomus, the frog-mouthed goatsucker. There still remain, however, a large number of Malayan genera absent from the Philippines, while there are a few Australian and Indian or Chinese genera which are not Malayan. '\Ve must also note that about nine-tenths of the mammalia and two-thirds of the land-birds are peculiar species, a very much larger proportion than is found on any other Malay islanJ. The origin of these peculiarities is not difficult to trace. The Philippines are almost surrounded by deep sea, but are connected with Borneo by means of two narrow submarine banks, on tile northern of which is situated Palawan, and on the southern the Sooloo 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 pn.rt become modified into distinct local species. They have also received a few Chinese types by the route aJready indicated, and a few Australian forms owing to their proximity to the Moluccas. The reason of their comparative poverty in genera |