FLYING ANIMALS. 35 



Flying Lemur seems to show us how an ordinary 

 Insectivore may have become gradually modified into 

 a Bat ; for it would only require the elongation of the 

 fingers and a somewhat greater development of the 

 parachute to transform the Flying Lemur- into a 

 creature exceedingly like a Bat. 



Bats, which are familiar to all of us, are the only 

 Mammals endued with the power of true flight ; and 

 although they are evidently related, as shown, among 

 other features, by the structure of their teeth, to the 

 Insectivores, yet they are so different as to be entitled 

 to rank as a separate order by themselves. In being 

 the only truly flying Mammals they hold, as has been 

 well observed, a position in the class precisely analogous 

 to that occupied among the Eeptiles by the Ptero- 

 dactyles. That they have, however, no sort of connec- 

 tion with the latter group is perfectly evident from 

 the structure of the fore-limb, or wing, which we now 

 proceed to explain. 



The wing of a Bat is composed of a thin naked 

 membrane supported by a great extension of the bones 

 of the fore-limb ; this membrane being continued 

 backwards to connect the hind-legs with the whole 

 length of the tail. In the fore-limb, of which the 

 skeleton is represented in Fig. 13, the bones of both 

 the arm and fore-arm are relatively slender and 

 considerably more elongated than usual. The thumb 

 remains comparatively small, and ends in a claw ; but 

 all the other fingers more especially the third or 

 middle one are enormously elongated, so that the 



