The Malay archipelago : the land of the orang-utan ... - Wallace Online

12 THE MALAY ARCHIPELAGO. [chap.thrushes, and leaf-thi'ushes : they are seen daily, and form the^reat ornithological features of the country. In tlie EasternIslands tliese are absolutely unknown, honeysuckers and smalllories being the most common birds ; so that the naturalist feelshimself in a new world, and can hardly realize that he has passedfrom the one region to the other in a few days, witliout everbeing out of sight of land.The inference that we must draw from these facts is undoubtedly,that the whole of the islands eastwards beyondJava and Borneo, with the exception, perhaps, of Celebes, doessentially form a part of a former Australian or Pacific continent,although some of tliem may never have been actuallyjoined to it. This continent must have been broken np notonly before the Western Islands wei'e separated from Asia,but probablj^ before the extreme south-eastern portion of Asiawas raised above the waters of the ocean ; for a great partof the land of Borneo and Java isknown to be geologically ofquite recent formation, while the very great difference of species,and in many cases of genera also, between the productions of theEastern Malay Islands and Australia, as well as the great depthof the sea now separating them, all jDoint to a comparativelylong period of isolation.It is interesting to observe among the islands themselves,liow a shallow sea always intimates a recent land-connexion.The Aru Islands, Mysol, and Waigiou, as well as Jobie, agreewith New Guinea in their species of mammalia and birds muchmore closely than they do with the Moluccas, and we find thatthey are all united to Xew Guinea by a shallow sea. In fact,the 100-fathom line round New Guinea marks out accuratelythe range of tlie true Paradise birds.It is further to be noted—and this is a very interesting pointin connexion with theories of the dependence of special formsof life on external conditions—that tliis division of the Archipelagointo two regions characterized by a striking diversity intheir natural pi'oductions, does not in any way correspond tothe main physical or climatal divisions of the surface. Thegreat volcanic chain runs througli both parts, and appears toproduce no effect in assimilating their productions. Borneoclosely I'esembles New Guinea, not only in its vast size and itsfreedom fi"om volcanoes, but in its variety of geological structure,its uniformity of climate, and the general aspect of the forestvegetation that clotlies its surface. The Moluccas ai-e the counterpartof the Philijipines in their A'olcanic structure, theirextreme fertility, their luxuriant forests, and their frequentearthquakes ;and Bali with the east end of Java has a climatealmost as dry and a soil almost as arid as that of Timor. Yetbetween tliese corresj^onding groups of islands, constructed asit were after the same pattern, subjected to the same climate,and bathed by the same oceans, there exists the greatest possiblecontrasts when we compare their animal productions. Nowhere