482 MR. A. R. WALLACE ON THE [NoV. 24, 



are identical with those of Java or Australia show the proportionate 

 influence of the two countries in a yet more striking manner. 



7 14 36 



This tahle shows how two streams of immigration have entered 

 the islands, the one from Java diminishing in intensity as it flowed 

 on to Timor, the other from Australia diminishing in about the same 

 degree towards Lombock. The total number of species which have 

 entered on the two sides seems nearly equal, with only a slight pre- 

 ponderance in favour of Australia ; but there is this remarkable dif- 

 ference, that whereas the great majority of the species derived from 

 Java are identical with the present inhabitants of that island, those 

 derived from AustraUa are for the most part representative species, 

 less than half of them being identical with birds still living in that 

 country. We shall see this perhaps more clearly by treating the 

 islands as a whole, and dividing that portion of their birds which 

 have exclusive relations to Java or Australia in a similar manner j 

 thus the Timorese avifauna contains 



Javan species 35 Australian species 13 



Javan representatives . . 11 Australian representatives. . 35 



46 48 



showing that, though the total number of species derived from the 

 two districts is nearly the same, the identical species and representa- 

 tives are divided in exactly reverse proportions. This fact is one of 

 the most important that we can draw from a consideration of these 

 lists of species, since it gives us a clue to the manner in which this 

 Httle group of islands was first slocked with animal life, and, in con- 

 nexion with geological considerations, will enable us to form a general 

 idea of their early 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 there- 

 fore indicate that the district 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 300 miles of 

 open sea now separates Austraha from Timor, which island is con- 



