H^LOBATES HOOLOCK, THE GIBBON 407 



exceptional length of the forearm which so increases the entire length of the 

 arm that the tips of the lingers touch the ground when the animal stands 

 erect. The slender hand is longer than the foot and the thumb is also long in 



FIG. 188. HYLOBATES SYNDACTYLUS (GIBBON). 



Gibbon's brachiating locomotion has favored erect posture and thus initiated the Proanthropoid Stage. 



proportion. These animals are possessed of remarkable vocal power and can 

 be heard for great distances. They go in troupes and usually early in the 

 morning give voice to their peculiar chorus of calls which seems to cease, as if 

 regulated by some prearranged schedule, in the early forenoon. 



