Indo-Malay Islands. 158 



the bats of each island are almost, if not quite, as distinct as 

 the other mammals. For example, sixteen species are known 

 in Borneo, and of these ten are found in Java and five in Su- 

 matra, a proportion about the same as that of the Rodents, 

 which have no direct means of migration. We learn from 

 this fact, that the seas which separate the islands from each 

 other are wide enough to prevent the passage even of flying 

 animals, and that we must look to the same causes as having 

 led to the present distribution of both groups. The only suf- 

 ficient cause we can imagine is the former connection of all 

 the islands with the continent, and such a change is in perfect 

 harmony with what we know of the earth's past history, and 

 is rendered probable by the remarkable fact that a rise of 

 only three hundred feet would convert the wide seas that 

 separate them into an immense winding valley or plain about 

 three hundred miles wide and twelve hundred long. 



It may, perhaps, be thought that birds which possess the 

 power of flight in so pre-eminent a degree would not be lim- 

 ited in their range by arms of the sea, and would thus afford 

 few indications of the former union or sepai'ation of the isl- 

 ands they inhabit. This however is not the case. A very 

 large number of birds appear to be as strictly limited by 

 watery barriers as are quadrupeds ; and as they have been 

 so much more attentively collected, we have more complete 

 materials to work upon, and are enabled to deduce from 

 them still more definite and satisfactory results. Some 

 groups, however, such as the aquatic birds, the waders, and 

 the birds of prey, are great wanderers ; other groups are lit- 

 tle known except to ornithologists. I shall therefore refer 

 chiefly to a few of the best known and most remarkable fam- 

 ilies of birds, as a sample of the conclusions furnished by the 

 entire class. 



The birds of the Indo-Malay region have a close resem- 

 blance to those of India ; for though a very large proportion of 

 the species are quite distinct, there are only about fifteen pe- 

 culiar genera, and not a single family group confined to the 

 former district. If, however, we compare the islands with 

 the Burmese, Siamese, and Malayan countries, we shall find 

 still less difference, and shall be convinced that all ai-e closely 

 united by the bond of a former union. In such well-known 



