No. 537] ZOOGEOGRAPHY OF THE EAST INDIES 543 



As to the worth of zoogeographic data in explanation 

 of these phenomena of dispersal, we must consider the 

 frequent impossibility of gathering all the evidence 

 bearing on the subject. This is not the place to do more 

 than set forth in niereM generality the justification for 

 the assertions made in the following outline. These 



continuing, with careful circumspection, to compare 

 most inquisitively all the available facts, being certain 

 that many important conclusions will be readied in the 

 end. In this manner I purpose to give here a review of 

 that which has already been learned regarding the Indian 

 Archipelago. 



The Indo-Australian Archipelago is, from a zoogeo- 

 graphie point of view, a region of the highest impor- 

 tance. It owes this special prominence to its lying upon 

 the boundary of two ureal kingdoms, the Indian and the 

 Australian, which show a greater faunistic differentia- 

 tion between one another than the rest of the old world. 



Sal. Mtiller first noticed this difference which exists 

 between the western and the eastern portions of the 

 Archipelago; and, following the teachings of his time, 

 he laid this distinction to the influence of climate and 

 natural conditions; so that while the western half has a 

 purely Indian character, the eastern portion— the is- 

 lands of which, generally speaking, are smaller — form 

 an area of transition to the conditions which obtain in 

 Australia. Miiller in his conclusions came in reality 

 nearer to the present opinion than did Wallace; but the 

 real, underlying causes of the differences remained, of 

 course, hidden from him. The boundary between both 

 regions he drew through the Straits of Macassar, and 

 in the south between the islands of Snmbawa and Flores; 

 while with some doubts he placed the island of Mindanao 

 in the eastern, and the remaining Philippine islands in 

 the western, section of the group. 



The first to bring geologic explanations to aid in ex- 

 plaining the faunistic differences between the eastern 

 and the western parts of the archipelago was Earl. But 



