XVII 



SPECIES OF GIBBON 



571 



compared with other Anthropoids is the fact of the large size of 

 the canines, which are of equal or nearly equal size in the two 

 sexes. The molars on the other hand have been particularly 



Fio. 272. — Hoolock. Hylobates hoolock. x J. 



compared to those of Man. The brain is simpler than in the 

 higher form's. But it is not clear that this may not be a case 

 of diminished complexity of convolution going hand in hand 

 with smallness of size. 



The Gibbons range through south-eastern A.sia from Assam 

 and Burmah to Hainan. The number of species is a little 

 doubtful. It is clear that in the first place we may distinguish 

 the Siamang, IT. synclactylus, which indeed some regard as a 

 separate genus. It is mainly to be defined by the syndactylous 

 character of the second and third toes ; they are united by skin 

 as far as the last joint. The Hainan species, H. hainamts, is 

 probably distinct, and the following names have been given to 

 various other species or races, viz. H. agilis, H. huciscus, H. leuco- 

 genys, H. lar, H. hoolock. These animals can walk erect ; and 

 when they do so, the big toe is separated as in unsophisticated 

 or at least unbooted man. The voice is well known to be loud, 



