MEANS OF MOTION 113 



ards has become so strictly toe-walking as to make 

 only three toe-tracks, the two outer toes being so 

 much shorter than the others that they do not touch 

 the earth when the foot is stretched up (Fig. 56). 



The flying-dragon (Fig. 5Y) — one of the tree-lizardB 

 — ^has the most remarkable apparatus in Nature out- 

 side of the birds for gliding down on the air. 



In the fossil flying lizard (Figs. 44 and 76) al- 

 ready noted, the flight was by a member attached to 

 the little finger. In fact, bats and even birds fly by 

 their fingers. Flying mammals glide on the air by 

 means of a fold of skin stretched along the body 

 which is attached to and spread out by the limbs. 

 But this modem flying Jizard spreads a similar mem- 

 brane by means of its ribs, which project outside of 

 the body, another most remarkable use of these bones. 

 They can be folded down by the side when not in use. 

 There is no power of fluttering, however. 



Crocodilians are able to make quite vigorous dashes 

 at an enemy on land, but since the projections on the 

 sides of the back -bone are long and close together, 

 they can not bend the neck or the body much, and 

 are therefore unable to turn quickly. They may be 

 dodged by a leap to one side. In the water they 

 swim well by means mostly of the flattened tail, but 

 they are said to roll over and over when they have 

 caught an animal, that they may confuse and more 

 quickly drown it. 



Perhaps it may be worth while here to remark 

 that reports of a snake's progress by means of taking 

 its tail in the mouth and rolling as a hoop is a myth, 



