214 Natukal History 



are divided in exactly a reverse manner, tliree-fourths of the 

 Javan birds being identical species and one-fourth representa- 

 tives, while only one-fourth of the Australian forms are iden- 

 tical and three-fourths representatives. This is the most im- 

 23ortant fact which we can elicit from a study of the birds of 

 these islands, since it gives us a very complete clew to much 

 of their past history. 



Change of species is a slow process. On that we are all 

 agreed, though we may differ about how it has taken place. 

 The fact that the Australian species in these islands have 

 mostly changed, while the Javan species have almost all 

 remained unchanged, would therefore indicate that the dis- 

 trict was first peopled from Australia. But, for this to have 

 been the case, the physical conditions must have been very 

 different from what they are now. Nearly three hundi'ed 

 miles of open sea now separate Australia from Timor, which 

 island is connected with Java by a chain of broken land 

 divided by straits which are nowhere more than about twen- 

 ty miles wide. Evidently there are now great facilities for 

 the natural productions of Java to spread over and occupy 

 the whole of these islands, while those of Australia would 

 find very great difficulty in getting across. To account for 

 the present state of things, we should naturally suppose that 

 Australia was once much more closely connected with Timor 

 than it is at present ; and that this was the case is rendered 

 highly probable by the fact of a submarine bank extending 

 along all the north and west coast of Australia, and at one 

 place approaching within twenty miles of the coast of Timor. 

 This indicates a recent subsidence of North Australia, which 

 probably once extended as far as the edge of this bank, be- 

 tween which and Timor there is an unfathomed depth of ocean. 



I do not think that Timor was ever actually connected 

 with Australia, because such a large number of very abun- 

 dant and characteristic groups of Australian birds are quite 

 absent, and not a single Australian mammal has entered Ti- 

 mor ; which would certainly not have been the case had the 

 lands been actually united. Such groups as the bower birds 

 (Ptilonorhynchus), the black and red cockatoos (Calypto- 

 rhynchus), the blue wrens (Malurus), the crowshrikes (Crac- 

 ticus), the Australian shrikes (Falcunculus and Colluricin- 



