322 



NATURAL HISTORY 



[chap. XIV. 



play ; while the vicinity of Lombock to Bali and Java 

 has allowed a continual influx of fresh individuals which, 

 by crossing with the earlier immigrants, has checked 

 variation. 



To simplify our view of the derivative origin of the 

 birds of these islands let us treat them as a whole, and 

 thus perhaps render more intelligible their respective rela- 

 tions to Java and Australia. 



The Timor group of islands contains : — 



Javan birds 36 



Closely allied species . . 11 



Derived from Java . . 47 



Australian birds . . 

 Closely allied species . 



Derived from Australia 



13 



35 



48 



We have here a wonderful agreement in the number of 

 birds belonging to Australian and Javanese groups, but 

 they are divided in exactly a reverse manner, three-fourths 

 of the Javan birds being identical species and one-fourth 

 representatives, while only one-fourth of the Australian 

 forms are identical and three-fourths representatives. This 

 is the most important fact which we can elicit from a 

 study of the birds of these islands, since it gives us a very 

 complete clue 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 



