212 Natueal History 



Archijielago that it is impossible to trace them as having 

 come from any one part rather than from another. There 

 are fifty-seven such species in my list, and besides these there 

 are thirty-five more which, though peculiar to the Timor 

 group, are yet allied to wide-ranging forms. Deducting these 

 ninety-two species, we have nearly a hundred birds left whose 

 relations with those of other countries we will now consider. 

 If we first take those species which, as far as we yet know, 

 are absolutely confined to each island, we find in 



Lombock 4, belonging to 2 genera, of which 1 is Australian, 1 Indian 

 Flores .12 " 7 " 5 are " 2 " 



Timor . 42 " 20 " 16 " 4 " . 



The actual number of peculiar species in each island I do not 

 suppose to be at all accurately determined, since the rapidly 

 increasing numbers evidently depend upon the more exten- 

 sive collections made in Timor than in Flores, and in Flores, 

 than in Lombock ; but what we can depend more upon, and 

 what is of more especial interest, is the greatly increased pro- 

 portion of Australian forms and decreased proportion of In- 

 dian forms, as we go from west to east. "We shall show this 

 in a yet more striking manner by counting the numbers of 

 species identical with those of Java and Australia respective- 

 ly in each island — thus : 



In Lombock. 



Javan birds 33 



Australian birds 4 



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 ofiers an obstacle, 

 and thus a smaller number get over to the next island.' 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 Ti- 

 mor. But this would be a hasty and, as we shall soon see, 

 an unwarranted supposition. Besides these birds identical 



' 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. 



