360 ZOOLOGICAL GEOGRAPHY. [PART III, 
broken up into many small volcanic islets in which a limited 
number of Malayan types alone survived. Such a condition of 
things will account for the very small variety of mammalia com- 
pared with the tolerably numerous genera of birds, that now 
characterise its fauna; while both here and in Celebes we find 
some of the old Malayan types preserved, which, in the extended 
area of the Sunda Isles have been replaced by more dominant 
forms. 
The next important change would be the separation of Java; 
and here also no doubt a considerable submergence occurred, 
rendering the island an unsuitable habitation for the various 
Malay types whose absence forms one of its conspicuous features. 
It has since remained permanently separated from the other 
islands, and has no doubt developed some peculiar species, while 
it may have preserved some ancient forms which in the larger 
area have become changed. From the fact that a number of its 
species are confined either to the western or the eastern half of 
the 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-Chinese 
forms, as already referred to in the earlier part of this sketch. 
We have thus shown how the main zoological features of the 
several sub-divisions of the Malayan sub-region may be 
accounted for, by means of a series of suppositions as to past 
changes which, though for the most part purely hypothetical, 
are always in accordance with what we know both of the 
physical geography and the zoology of the districts in question 
and those which surround them. It may also be remarked, that 
we know, with a degree of certainty which may be called absolute, 
that alternate elevation and subsidence is the normal state of 
things all over the globe; that it was the rule in the earliest 
geological epochs, and that it has continued down to the 
historical era. We know too, that the amownt of elevation and 
subsidence that can be proved to have occurred again and again 
in the same area, is often much greater than is required for the 
changes here speculated on,—while the ¢ime required for such 
changes is certainly less than that necessitated by the changes 
