LIFE IN LONDON 397 



entered these islands, the one from Java diminishing in 

 intensity as it passed on farther and farther to Timor; the 

 other from Australia entering Timor and diminishing still 

 more rapidly towards Lombok. This indicates, as its geologi- 

 cal structure shows, that Timor is the older island and that 

 it received immigrants from Australia at a period when, 

 probably, Lombok and Flores had not come into existence 

 or were uninhabitable. This is also indicated by the fact that 

 the Australian immigrants have undergone greater modifica- 

 tion than the Javan. If we compare the birds of the whole 

 chain of islands according as they are of Javan or Australian 

 origin, we have the following results: — 



Javan species 36 Australian species 13 



Javan allied species 1 1 Australian allied species. . 35 



47 48 



We thus see that while the proportion of the birds derived 

 from each source is almost exactly equal, about three-fourths 

 of those from Java have remained unchanged, while three- 

 fourths of those from Australia have become so modified as 

 to be very distinct species. This shows us how the distribu- 

 tion of birds can, when carefully studied, give us information 

 as to the past history of the earth. 



We can also feel confident that Timor has not been 

 actually connected with Australia, because it has none of the 

 peculiar Australian mammalia, and also because many of the 

 commonest and most widespread groups of Australian birds 

 are entirely wanting. And we are equally certain that Lom- 

 bok and the islands further east have never been united to 

 Bali and Java, because four Australian or papuan genera 

 of parrots and cockatoos are found in them, but not in Java, 

 as are several species of honey suckers (Meliphagidse), a fam- 

 ily of birds confined to the Australian region. On the other 

 hand, a large number of genera which extend over the whole 

 of the true Malay islands, from Sumatra to Java, never pass 

 the narrow straits into Lombok. Among these are the long- 

 tail parrakeets (Palseornis), the barbets (Megalaemidae), the 



