GEOGRAPHY OP THE MALAY ARCHIPELAGO. 179 
countries is least, and vice versd. But again, tlie mass of the 
species of Borneo, Java, &c., even when not identical are congeneric , 
which, as before explained, indicates identity at an earlier epoch ; 
whereas the great mass of the fauna of Celebes is widely different 
from that of the western islands, consisting mostly of genera, and 
even of entire families, altogether foreign to them. This clearly 
points to a former total diversity of forms and species, — existing 
similarities being the result of intermixture, the extreme facilities 
for which we have pointed out. In the case of the great western 
islands a former more complete identity is indicated, the present 
differences having arisen from their isolation during a considerable 
period, allowing time for that partial extinction and introduction 
of species which is the regular course of nature. If the very small 
number of western species in Celebes is all that the most favour- 
able conditions for transmission could bring about, the complete 
similarity of the faunas of the western islands could never (with 
far less favourable conditions) have been produced by the same 
means. And what other means can we conceive but the former 
connexion of those islands with each other and with the continent 
of Asia ? 
In striking confirmation of this view we have physical evidence 
of a very interesting nature. These countries are in fact still 
connected , and that so completely that an elevation of only 300 
feet would nearly double the extent of tropical Asia. Over 
the whole of the Java Sea, the Straits of Malacca, the Gulf of 
Siam, and the southern part of the China Sea, ships can anchor in 
less than fifty fathoms. A vast submarine plain unites together 
the apparently disjointed parts of the Indian zoological region, and 
abruptly terminates, exactly at its limits, in an unfathomable ocean. 
The deep sea of the Moluccas comes up to the very coasts of 
Northern Borneo, to the Strait of Lombock in the south, and to 
near the middle of the Strait of Macassar. May we not therefore 
from these facts very fairly conclude that, according to the system 
of alternate bands of elevation and depression that seems very 
generally to prevail, the last great rising movement of the volcanic 
range of Java and Sumatra was accompanied by the depression 
that now separates them from Borneo and from the continent ? 
It is worthy of remark that the various islands of the Moluccas, 
though generally divided by a less extent of sea, have few'er species 
in common ; but the separating seas are in almost every case of 
immense depth, indicating that the separation took place at a much 
earlier period. The same principle is well illustrated by the dis- 
12 * 
