CHEIROPTERA, OE BATS. 285 



air cells beneath the skin. The various diodon 

 fishes possess a similar power; but in them it is 

 probably used as a means of defence, the swollen 

 body causing the multitudinous spikes with which it 

 is armed to stand out like the prickles of a rolled-up 

 hedgehog 1 . 



It has been proved that the wings possess more 

 points of interest than is generally known. 



They are almost as elastic as if made of India- 

 rubber, and nearly as delicate as goldbeaters' skin, 

 so that, when the creature is at rest, they fall of 

 their own accord into folds that occupy very little 

 space, and do not interfere with their owner's move- 

 ments. 



They also act as a cradle for the infant young; 

 but one of their principal uses, in addition to that of 

 flight, is their power of directing the course of the Bat 

 as it flies through the air. Anatomists have often 

 been struck with the fact that, according to the usual 

 custom of nocturnal animals, the insect-eating Bats 

 have very small eyes. Taking as examples of dark- 

 ness-loving and predatory creatures, the owls, the 

 lemurs, and even the domestic cat, we find that the 

 eyes are very large, and we might naturally expect 

 that we should find a similar structure in the Bats. In 

 them, however, the eyes are very small, and there is 

 reason to suppose that they are not much brought into 

 requisition in the capture of flies, moths, and other 

 insects which form the chief food of the Bat. 



Many years ago, a series of experiments were 

 instituted by Spallanzani, who had been struck with 

 the fact that Bats could fly with confidence in a 



