23.i Merrill: Distribution of Dipterocarpaceae 15 



of birds and insects are curiously limited in distribution, indicat- 

 ing that some at least do not extend their range except over con- 

 tinuous land areas. Each specialist is, of course, interested in 

 his own group, and it is but natural that he should be influenced 

 in his deductions by his own special knowledge and his own 

 special interests. Thus Pelseneer, 16 on the basis of certain 

 geographic distributional studies, abandoned Wallace's Line and 

 constructed a new one east of Celebes and Timor; this new line, 

 which he called Weber's line, is absolutely untenable when all 

 groups of animals are considered, even as Wallace's Line is 

 untenable as an absolutely separating boundary. 



Weber's Line is, however, apparently the approximate eastern 

 boundary of the geologically unstable intermediate insular area, 

 and bears much the same relationship to the Australian con- 

 tinent that Wallace's Line bears to the Asiatic continent. It 

 seems to be clear that different portions of these lines have 

 distinctly different values (see Plate 2). 



Wallace's Line, so named by Huxley, was placed between Bali 

 and Lombok, extending northward through the Macassar Strait 

 between Borneo and Celebes and thence turning to the eastward 

 between Celebes and Mindanao, extending into the Pacific Ocean. 

 It was based on observations and published statements of Alfred 

 Russell Wallace regarding the evident differences in the biology 

 of eastern and western Malaysia. Critics of Wallace's Line have 

 not always been entirely fair to Wallace. In his Island Life he 

 clearly states that Celebes, although included by him in the Aus- 

 tralian region, from a balance of considerations, almost equally 

 belongs to the Oriental Region, and that it consequently must be 

 left out of account in the general sketch of the zoological features 

 of the Australian Region. Again, he speaks of it as an "anom- 

 alous island" because both by what it has and by what it wants 

 it occupies such an exactly intermediate position between the 

 Australian and Oriental Regions. 



In reference to the position of Wallace's Line, our present 

 data seem to show that this fundamental dividing line does not 

 turn to the east between Celebes and Mindanao, but extends 

 northward through the Sibutu Passage, the Sulu Sea, and the 

 Mindoro Strait between the Calamian group and Mindoro, thence 

 northward and then eastward between Formosa and the Batan 

 Islands into the Pacific. The extension of this line north of 



