THE BRONTOSAUR AND ITS COUSINS 65 



expanded wings and jaws that would bite a square 

 foot of flesh out of an elephant. 



This variety is an expression of the struggle for 

 life. Every little advantage for escape was favoured 

 and strengthened during hundreds of thousands of 

 years of conflict, and the branches of the family 

 spread in all directions. Some went down into the 

 sea, where great sharks v/ere their only competitors. 

 Some developed powerful back legs, and could outpace 

 even a running carnivore. They were often far larger 

 than the giant kangaroo, and must have been able to 

 do a remarkable "long jump." Some climbed trees, 

 and it is probably from these relatively small and 

 active creatures that the flying reptiles were evolved. 

 Some think that flying began with running, but it 

 seems more likely that its origin was in leaping down 

 from low branches of trees when a pursuer mounted 

 the tree. Webby fore-feet would be an advantage. 

 The animal could, in our aeronautical language, glide 

 or plane down to the ground; and a long course of 

 this evolution of "webbiness" would at last give a 

 powerful membrane from the first toe (which grew to 

 a length of several feet) to the side of the body — the 

 plane or wing of the flying reptile. 



As far as general principles are concerned, therefore, 

 we very fairly understand the wonderful family of 

 reptiles — some writers strangely persist in calling 

 them "lizards" — which filled the land, the waters, 

 and the air of the earth's Middle Ages. There are a 

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