254 ANTHROPOID APES. 



appears to live more commonly in pairs than in 

 troops. We learn from Duvaucel that these animals 

 move through the trees with great swiftness, grasp- 

 ing the slenderest and most flexible branches. They 

 swing two or three times to and fro, and then spring 

 with outstretched arms so that the fiat surface of 

 the body resists the air like a parachute, and in this 

 way they can pass through spaces of forty feet, and 

 go on for hours without fatigue. 



Gibbons are generally more capable than other 

 anthropoids of walking upright. Some species, 

 such as the lar, the white-handed, and the slender 

 gibbon, display special dexterity and endurance in 

 maintaining this position. They press the flat soles 

 of their feet upon the ground, turn out their knees 

 and toes, hold their bodies fairly erect, draw the 

 shoulders together, and place their half-bent arms 

 by their sides, with the slender hands hanging 

 slackly down. Others walk with their raised arms 

 crossed above the head. When a gibbon is walking 

 on perfectly flat ground, he sways his arms to 

 and fro like balancing poles. On irregular ground 

 they seize any projection in the way with their out- 

 stretched arms, and, holding on to it, swing the 

 body strongly forwards. In this way they make 

 better progress over wide tracks of country, since 

 every such effort enables them to pass more readily 

 over difficult ground. When in great haste, they 

 go upon all fours without closing either fingers 

 or toes. In repose, these animals take a sitting 

 position upon their posteriors, cross their long arms 

 and stare at whatever is before them with an air 



