544 MANUAL OF ZOOLOGY sect. xii. 



never prehensile. The pollex when developed is always 

 opposable to the other digits. In the Simiidae or man-like 

 apes, a tail is never developed, and there are no cheek- 

 pouches ; ischial callosities are only present in the gibbons. 

 The gibbons can walk in an upright position without the 

 assistance of the fore-limbs ; in the others, though in pro- 

 gression on the surface of the ground, the body may be held 

 in a semi-erect position with the weight resting on the hind- 

 limbs, yet the assistance of the long fore-limbs acting as 

 crutches is necessary to enable the animal to swing itself 

 along. 



