THE ALLIES OF THE SQUIRREL: MAMMALIA 423 



So well adapted for aerial locomotion have the bats (Fig. 

 224) become that progress on the ground is almost impossible. 

 .The sense of touch is greatly developed not only on the 

 muzzle but on the wings 

 as well, so that the animals 

 are able to avoid obstacles 

 in their nocturnal flights. 

 During the day bats hang 

 themselves up by their legs 

 to sleep in caves and in 

 hollow trees. Some species 

 feed on insects, others on 

 fruit, and some, the vampire 

 bats of Central and South 

 America, feed on blood. 

 The latter have the teeth 

 peculiarly adapted to cut- 

 ting, the skin of animals. 

 The (Bsophagus is so nar- 

 row that no solid matter 

 can pass down it. 



Primates. The Prima'tes 

 (Lat. primus, first) include 

 the monkeys, apes, and 

 ,man. The teeth are gener- 

 ally adapted to a diet of 



FIG. 224. Photograph of Bat 



both plant and animal food ; the five toes and fingers are sepa- 

 rate and are usually provided with nails; the thumb is oppos- 

 able to the other digits, and the eyes are directed forward. 



The spider-monkeys (At'eles, Fig. 225) of South and Cen- 

 tral America are representative forms of the New World 

 monkeys. They have a long tail, which serves as an organ 

 of prehension. The most man-like of the monkeys are the 

 orang-utan (Sim'ia sat'yrus) of Borneo and Sumatra, and the 



