184 PONGO 
the native hunters. And in this he would be fully justified, for those 
of us who have had experience with native collectors in savage lands, 
know perfectly well that the localities they give their specimens 
cannot often be relied upon. However this may be, these Ourang skulls 
are without any particular locality, but simply have marked on them 
a letter to indicate the district from which each one supposedly came. 
Thus S. stands for Skalau District; B. for Batangtu; D. for Dadapai; 
G. for Genepai; L. for Landak; R. for Rantau; and some half dozen 
were found, all very young skulls, to represent the races he called 
tuakensis, obongensis, and wallacei. Another fact in regard to these 
skulls, was the infinite variations they exhibited. No two in the 280 
were alike, and even some from the same locality, or at all events the 
same district, varied to an amazing degree. A study of this material 
proved that an attempt to establish species upon cranial characters 
would be futile, and it may be for that reason Herr Selenka did not 
attempt it, but endeavored to found his species upon the cubical di- 
mensions of the interior of the braincase, about as hopeless a pro- 
ceeding, as to try to subject the endless variations of the rest of 
the crania to some degree of uniformity. This was the only material 
available for the determination of species, and other interesting points 
connected with the Ourang-utan. A large series of crania, the largest 
in existence, mostly those of very young animals, and females, only 
a few of the latter being adult, and some old adult males, (of these 
last I was able to select eighteen out of the lot), none of which had 
a particular locality given to it, and no skins for any of them. The 
outlook was far from encouraging, but the material was the best in 
existence, lamentably defective as it was in most important points. 
Nothing could be done towards the solution as to the cause of the 
presence or absence of callosities, and although we knew from Selenka’s 
statements, that individuals with and without callosities were obtained 
in the same districts, the skulls gave no sign as to whether they had 
been present or not. 
Herr Selenka bases his species mainly upon the cubical dimensions 
of the interior of the braincase, and upon certain theories, for much 
of which he has produced no proofs. According to his own tables, 
cubical dimensions are very unsatisfactory characters, for rarely do 
two crania agree in their dimensions, and we must regard this method 
as one quite unsuitable per se, for the determination of the species. 
His theory is as follows: Borneo is intersected by wide and deep 
rivers, and since Ourangs can neither swim rivers, nor climb moun- 
tains, they are hemmed in on sections of land as if on islands, and 
