162 DOCTRINE OF EVOLUTION 



and sureness in climbing about is partly due to the per- 

 fect grasping power of the lower limb. To all intents 

 and purposes the foot is a hand ; the first toe is shorter 

 than the others, and its free motion is unrestricted as in 

 the thumb of the hand. These animals usually possess 

 a long tail which they can use as a prehensile organ, 

 curling it about the branch of a tree with hand-like 

 ease and grasp. When they run on all fours, they 

 plant the palms and soles flat upon the ground. The 

 feature of primary importance in a comparative sense 

 is the advanced structure of the skull. These anthro- 

 poids are much more intelligent than the lower forms, 

 which is a correlate of their larger and more convoluted 

 brains. The increase in the total bulk of the brain 

 has wrought considerable change, not only in the head, 

 but also in the relation of head to the trunk. The 

 cranium, or brain-case of bone, is relatively larger than 

 the ^'face," and it bulges upward so as to lie no longer 

 behind the latter as it does in the lower mammalia. 

 In consequence of this cranial enlargement, the face 

 and eyes are swung downward, as it were, so that the 

 line of vision is not straight ahead, but depressed below 

 the horizontal. In order to look to the front and to the 

 immediate foreground to which it is progressing or to 

 where its food or enemies may be, the monkey must 

 bend back its head ; if it is still, it finds greater ease 

 in the upright sitting posture which it assumes readily 

 and naturally. 



The next division, called the Cercopithecidse, in- 

 cludes the baboons of the Old World. These animals 

 also run upon all fours, and their feet are handlike as 

 before, but the tail is much reduced. The general 



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