320 NATURAL HISTORY [chap. xiv. 



east. We shall show this in a yet more striking manner 

 by counting the number of species identical with those of 

 Java and Australia respectively in each island, thus : 



In Lomboclc. In Flores. In Timor. 

 Javan birds . . . 33 23 11 



Australian birds . . 4 5 10 



Here we see plainly the course of the migration which 

 has been going on for hundreds or thousands of years, and 

 is still going on at the present day. Birds entering from 

 Java are most numerous in the island nearest Java ; each 

 strait of the sea to be crossed to reach another island offers 

 an obstacle, and thus a smaller number get over to the 

 next island. 1 It will be observed that the number of 

 birds that appear to have entered from Australia is much 

 less than those which have come from Java ; and we may 

 at first sight suppose that this is due to the wide sea that 

 separates Australia from Timor. But this would be a hasty 

 and, as we shall soon see, an unwarranted supposition. 

 Besides these birds identical with species inhabiting Java 

 and Australia, there are a considerable number of others 

 very closely allied to species peculiar to those countries, 

 and we must take these also into account before we form 



1 The names of all the birds inhabiting these islands are to be found 

 in the " Proceedings of the Zoological Society of London " for the year 

 1863. 



