24 The Malay Archipelago. 



islands, and in some cases there seems also to have been time 

 for a change of species to have taken place. Birds and insects 

 illustrate the same view, for every family, and almost every 

 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 offer us one of the best 

 means of determining the law of distribution ; for though at first 

 sight it would appear that the watery boundaries which keep 

 out the land quadrupeds could be easily passed over by birds, 

 yet pi-actically it is not so ; for if we leave out the aquatic 

 tribes which are pre-eminently wanderers, it is found that the 

 others (and especially the Passeres, or true perching-birds, 

 which form the vast majority) are generally as strictly limited 

 by straits and arms of the sea as are quadrupeds themselves. 

 As an instance, among the islands of which I am now speak- 

 ing, it is a remarkable fact that Java possesses numerous birds 

 which never pass over to Sumatra, though they are separated 

 by a strait only fifteen miles wide, and with islands in mid- 

 channel. Java, in fact, possesses more birds and insects pe- 

 culiar to itself than either Sumatra or Borneo, and this would 

 indicate that it was earliest separated from the continent; 

 next in organic individuality is Borneo, while Sumatra is so 

 nearly identical in all its animal forms with the peninsula of 

 Malacca that we may safely conclude it to have been the most 

 recently dismembered island. 



The general result, therefore, at which we arrive is, that the 

 great islands of Java, Sumatra, and Borneo resemble, in their 

 natural productions, the adjacent parts of the continent, almost 

 as much as such widely-separated districts could be expected 

 to do even if they still formed a part of Asia ; and this close 

 resemblance, joined with the fact of the wide extent of sea 

 which separates them being so uniformly and remarkably shal- 

 low, and lastly, the existence of the extensive range of volca- 

 noes in Sumatra and Java, which have poured out vast quan- 

 tities of subterranean matter, and have built up extensive pla- 

 teaux and lofty mountain ranges, thus furnishing a vera causa 

 for a parallel line of subsidence, all lead irresistibly to the 

 conclusion that at a very recent geological epoch the continent 

 of Asia extended far beyond its present limits in a south-east- 

 erly direction, including the islands of Java, Sumatra, and 



