No. 537] ZOOGEOGRAPHY OF THE EAST INDIES 545 



and Timor, and which has been named by its author 

 "Weber's Line." But taking the fauna as a whole it is 

 quite certain that no line may be drawn ; but, rather, we 

 may lay out a transition zone in which the fauna of 

 India and that of Australia are mingled, and wherein 

 from the west to the east the Australian components in- 

 crease more and more in number; and on the other hand, 

 the Indian tend to die out. All of this region belongs to 

 the eastern half of the archipelago from Celebes to New 

 Guinea, and included in it we find a part of the Poly- 

 nesian 2 Islands ; but it is necessary to keep in mind that 

 even the boundaries of this transition region are not 

 sharply defined. 



The justice of the position taken here will presently 



vertebrate animals, especially from fresh-water fishes, 

 amphibians and mammals. All three groups, on account 

 of the small likelihood of their being spread abroad over 

 the sea, are of much importance to us. 



First of all, however, the origin of the fauna of Aus- 

 tralia merits a word. It is now commonly agreed that 

 in past times this island formed an essential part of Asia, 

 connected by a previously existing land-bridge which in- 

 cluded the archipelago as it exists to-day. Formerly this 

 connection was considered to have occurred during the 

 Jurassic period (Xeumayer's 1 1 Jura-Continent"). The 

 finding, however, of deep sea deposits laid down in 

 Jurassic times in different parts of the archipelago (e. g. t 

 on Borneo, Celebes and Bum) has made it seem more 

 probable that the mooted connection was delayed until the 



