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 are " 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 extensive 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 special interest, is the greatly increased proportion of Australian forms and decreased proportion of Indian forms, as we go from west to 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 Lombock. 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. [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.] 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 any conclusion on the matter. It will be as well to combine these with the former table thus:
In Lombock. In Flores. In Timor. Javan birds........ ... 33 23 11 Closely allied to Javan birds.. 1 5 6 Total.............. 34 28 17