rrEOGHlAPHT OF THE MALAY ABCHIPELAGO. 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 tlie 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 Grilolo, but not 

 New Guinea ; Pigs have extended to New Gruinea, probably the 

 true eastern limit of the genus Sus ; Squirrels are found in 

 Celebes, Lombock, and Sumbawa : among birds, Oallus occurs in 

 Celebes and Sumbawa, Woodpeckers reach Celebes, and Horn- 

 bills extend to the North-west of New Gruinea. These cases of 

 identity or resemblance in the animals of the two 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 Grrey Monltey {Macacus cynomolgus) 

 has reached Lombock, and perhaps Timor, but not Celebes. The 

 Deer of the Moluccas seems to be a variety of the Cervus rufus of 

 Java and Borneo. The Jungle Cock of Celebes and Lombock is a 

 Javanese species. Hirundo javanica, Zoster ops flavus. Halcyon 

 collaris, Eurystomus gularis, Macropygia phasianella, Merops 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 we help believing that n^any 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 



