7046 Quadrupeds. 



exactly in proportion as they are worn away at the extremities. The 

 lower jaw, like that of the other rodents, moves evidently by means of 

 a longitudinal condyle, so as to prevent any horizontal movement from 

 back to front, and vice versa. 



Here then is a powerful rodent possessing a very delicate sense of 

 hearing (a combination which induces me to believe the account of 

 the inhabitants of Madagascar, who assert that this animal listens to 

 the noise of the worm in the interior of the tree, and that it then gnaws 

 the wood until it has reached the worm, which it extracts with its long 

 and slender finger), a description applicable to many other rodents. 

 These animals, especially the mouse, the hare, the rabbit, and a still 

 larger animal, the chinchilla of South America, besides having strong 

 teeth designed for gnawing, are gifted with a very delicate sense of 

 hearing. Living in constant fear of the larger Carnivora this delicate 

 hearing is absolutely necessary to warn them of approaching danger; 

 while the Cheiromys or aye-aye, living in trees in a country where 

 there are no Carnivora of a magnitude to endanger its safety, has nothing 

 to fear from the attacks of enemies, so that its acute sense of hearing 

 must be provided rather as a means of attack than of defence. 



I had arrived at this point of my observations ; and, judging more 

 from the supposed food of the aye-aye and from his general confor- 

 mation than from his habits or his teeth, I had fed him with bananas 

 and dates, thinking, of course, that as he was adapted for living on 

 trees and had no canine teeth, far from being carnivorous he must be 

 frugivorous and insectivorous. 1 had him one evening in my room, 

 and observed all his movements. It was very curious to see him 

 climbing on the chairs and tables, and carefully observing the wood of 

 each piece of furniture. While he examined the partition I heard a 

 continued slight noise, which was quickly repeated, and I was some 

 time in discovering the cause. At last 1 remarked that from time to 

 time this little animal gave rapid, slight blows, which produced a 

 vibrating sound, with the second finger, that thin thread-like member 

 which resembles a bent wire, and by means of which it is said he draws 

 the worm from the; trees : while he thus struck the wood he seemed 

 to listen attentively. Once as he crossed my room, after having struck 

 the floor he began to tear the matting with his teeth. As I was not 

 disposed to allow him to destroy anything T was obliged to drive him 

 away, but I felt convinced that he did really eat the worms which he 

 found in wood, as it was related. Thus we have now among animals 

 what the woodpecker is among birds, for although the latter is insecti- 

 vorous it also lives on fruits and even on eggs. 



