GEOGRAPHY OF THE MALAY ARCHIPELAGO. 
175 
But it may be said : “ The separation between these two regions 
is not so absolute. There is some transition. There are species 
and genera common to the eastern and western islands.” This is 
true, yet (in my opinion) proves no transition in the proper sense 
of the word ; and the nature and amount of the resemblance only 
shows more strongly the absolute and original distinctness of the 
two divisions. The exception here clearly proves the rule. 
Let us investigate these cases of supposed transition. In the 
western islands almost the only instance of a group peculiar to 
Australia and the eastern islands is the Megapodius in North- 
west Borneo. Not one of the Australian forms of Mammalia 
passes the limits of the region. On the other hand, Quadrumana 
occur in Celebes, Batchian, Lombock, and perhaps Timor ; Deer 
have reached Celebes, Timor, Buru, Ceram, and Gilolo, but not 
New Guinea ; Pigs have extended to New Guinea, probably the 
true eastern limit of the genus Sus ; Squirrels are found in 
Celebes, Lombock, and Sumbawa : among birds, Gallus occurs in 
Celebes and Sumbawa, Woodpeckers reach Celebes, and Horn- 
bills extend to the North-west of New Guinea. These cases of 
identity or resemblance in the animals of the tw o regions we may 
group into three classes ; 1st, identical species ; 2nd, closely 
allied or representative species ; and 3rd, species of peculiar and 
isolated genera. The common Grey Monkey (Macacus cynomolgus) 
has reached Lombock, and perhaps Timor, but not Celebes. The 
Deer of the Moluccas seems to be a variety of the Cervm rufus of 
Java and Borneo. The Jungle Cock of Celebes and Lombock is a 
Javanese species. Hirundo javanica , Zosterops jlavus> Halcyon 
collar is, JEurystomus gularis, Macropygia phasianella, Meropts java- 
nicus, Anthreptes lepida , Ptilonopus melanocephala, and some other 
birds appear the same in the adjacent islands of the eastern and 
western divisions, and some of them range over the whole Archi- 
pelago. But after reading Lyell on the various modes of disper- 
sion of animals, and looking at the proximity of the islands, we 
shall feel astonished, not at such an amount of interchange of 
species (most of which are birds of great powers of flight), but 
rather that in the course of ages a much greater and almost com- 
plete fusion has not taken place. Were the Atlantic gradually to 
narrow till only a strait of twenty miles separated Africa from 
South America, can w r e help believing that many birds and insects 
and some few mammals would soon be interchanged ? But such 
interchange would be a fortuitous mixture of faunas essentially 
and absolutely dissimilar, not a natural and regular transition from 
