lii THE MALAY ARCBirmAGO, [chap.!. 



the gi-eat cluiin of activcj volcanoes in Sumatm and Java 

 fnTnislies us with a sufficient cause for such subsidence, 

 since the enomous masses of inatter they have tlirown 

 out would take away the foundations of the surrountljuif 

 district ; and this may be the true explanation of the 

 often-noticed factj that volcanoes and volcanic chains are 

 always near the sea. Tlie subsidence they produce around 

 them will, in time, make a sea, if one does not akeady 

 exist 



But it is when we examine tlic zoologj' of these countries 

 that we find what ^ve most require — evidence of a very 

 striking chai-acter that these gix^at islands muist have once 

 fomied a pait of the continent, and could only have been 

 separated at a very recent geologicfd epocL The elephant 

 and tapir of Sumatra and BomeOj the rhinoceros of 

 Sumatra and the allied species of Java, the wild cattle 

 of liomeo niid the kind long supposed to be peculiar to 

 Java, are now all known to inhabit some part or other 

 of Southern Asia. None of these lai^^e animals could 

 possibly have passed over the arms of the sea which now 

 sepai-ate these countries, and their presence plainly indi- 

 cates that a land communication must have existed smce 

 the origin of the species. Among the smaller mammals 

 a considerable portion are common to each island and tlie 

 continent ; but the vast physical changes that must have 

 occun*ed during tiie breaking up and subsidence of such 

 extensive regions have led to the extinction of some in 

 one or more of the islands > and in some cases there seems 

 also to have been time for a change of species to have 

 taken place. Birds and insects dhistmte the same view, 

 for every family, and ahnost eveiy genus of these 

 groups found in any of the islands, occurs also on the 

 Asiatic continent, and in a great number of cases the 

 species are exactly identical. Birds oiler ns one of the 

 liflsfc means of determining the law of distribution ; for 

 though at first sight it would appear that the watery 

 boundaries which keep out the land quath'upeds could be 

 easily passed over by birds, yet practically it is not so ; 

 for if we leave out the aquatic tribes which are pi-e- 

 eminently wanderers, it is found that the others (and 

 especially the Passeres, or true perching-birda, which form 



