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

;360 ZOOLOGICAL GEOGRAPHY. [past hi.broken up into many small volcanic islets in which a limitednumber of Malayan types alone survived. Such a condition ofthings will account for the very small variety of mammalia comparedwith the tolerably numerous genera of birds, that nowcharacterise its fauna ; while both here and in Celebes we findsome of the old Malayan types preserved, which, in the extendedarea of the Sunda Isleshave been replaced by more dominantforms.The next important change would be the separation of Javaand here also no doubt a considerable submergence occurred,rendering the island an unsuitable habitation for the variousMalay types whose absence forms one of its conspicuous features.It has since remained permanently separated from the otherislands, and has no doubt developed some peculiar species, whileit may have preserved some ancient forms which in the largerarea have become changed. From the fact that a number of itsspecies are confined either to the western or the eastern half ofthe island, it is probable that it long continued as two islands,which have become united at a comparatively recent period.It has also been subjected to the immigration of Indo-Chineseforms, as already referred to in the earlier part of this sketch.We have thus shown how the main zoological features of theseveral sub-divisions of the Malayan sub-region may beaccounted for, by means of a series of suppositions as to pastchanges which, though for the most part purely hypothetical,are always in accordance with what we know both of thephysical geography and the zoology of the districts in questionand those which surround them.It may also be remarked, thatwe know, with a degree of certainty which may be called absolute,that alternate elevation and subsidence is the normal state ofthings all over the globe ; that it was the rule in the earliestgeological epochs, and that it has continued down to thehistorical era. We know too, that the amount of elevation andsubsidence that can be proved to have occurred again and againin the same area, is often much greater than is required for thechanges here speculated on,—while the time, required for suchchanges is certainly less than that necessitated by the changes