Introduction; Wallace’s line. 
assigned to the great Sunda Islands, 3 to the eastern islands, that, therefore, 
no sharp frontier exists for land-shells between Bali and I.ombok. 
The same eminent conchologist said in 1897 (“Suss- und Brackwasser-Mol. 
des Indischen Archipels”: Weber’s Zool. Ergebnisse IV, 298): “The frontier between 
Bali and Lombok is for the fresh-water Mollusca quite imaginary, as long as we know 
next to nothing of the species living on these islands;” and he proved further 
(p. 297) that the fresh-water Mollusca from South Celebes are most closely 
allied to those of Java and Flores, those of North Celebes most closely to those 
of the Philippines, which is not consistent with Wallace’s line, but with the 
geographical position. 
A. Sup an, 1896 (“Grundztige der physischen Erdkunde”, p. 557, and Maps 
XIX, XX) sticks to the “celebrated” line. 
W. Kiikenthal, in 1896 (Abb. Senckenb. Naturf. Ges. XXII, 130), abnegates 
Wallace’s line. 
W. L. Sclater, 1896, treating of the Mammals of his Celebesian Subregion 
(“The Geography of Mammals”: Geogr. Journ. VIII, 388 with Maps), finds that the 
Australian element in the mammalian fauna of Celebes does not in any way 
require the supposition of an ancient land-connection with that Region, but that 
the greater amount of Oriental forms suggests such a former connection with Asia; 
he, therefore, annexes the Celebesian Subregion to the Oriental and not to the 
Australian Region. In the beginning of this important paper (1. c. 1894, III, 
p. 97, with Map, and IV, p. 35, with Map) Mr. Sclater draws Wallace’s line 
to the east of Celebes and between Bali and Lombok (see, also, 1. c VIII, p. 378) 
and takes this as the frontier between the Australian and the Oriental Region, 
reckoning the Sula Islands to the former, Celebes to the latter, as “on the whole 
the evidence of the mammals, at any rate, serves to connect it more closely with 
the Oriental Region” (see 1. c. IV p. 36). 
F. J. Niermeyer, finally, in 1897 (“De Geschiedenis van de lijn van 
Wallace”: Tijdschr. Kon. Ned. Aard. Gen. 2. ser. XIV, 758), has given a very 
readable historical sketch. He rightly censures zoologists, botanists, and geo- 
graphers for often writing on the problem without having consulted Wallace 
himself, or the manifold literature extant on this subject, and still advocating 
a frontier which specialists have long since abandoned. He shows in detail how 
Wallace himself has altered his opinion from 1860 to 1863, 1869, 1876, and 
1880, and what Weber’s merits are in promoting knowledge on this question. 
On going over these different opinions on Wallace’s line it will be seen 
that they are fairly equally divided, though they must be weighed and not 
counted, - many writers on the general subject not plunging deeply into the 
problem , but uncritically following the authority of this eminent naturalist. 
One must also take into account that errors, when once they have crept into 
books, disappear from them with great difficulty. On the other hand also, some 
