180 THE MEANING OF EVOLUTION 



lakes. Out upon the land others, not quite so heavy 

 nor so large, roamed about, some of them feeding 

 upon the soft vegetation, others having teeth fitted to 

 tear down their herbivorous cousins. In some of them 

 the hind legs and tail were very heavy and the front 

 legs so light that it is quite clear they must have 

 hopped around as do the kangaroos to-day. Others of 

 these reptiles went back to the sea, lost the leglike 

 development of their limbs and regained the flipper 

 form, though the bones of the fingers and toes are 

 singularly distinguishable in the paddle. 



Strangest of all, a considerable group of these 

 wonderful reptiles lengthened their little fingers, some- 

 times to three or four feet in length, and had a skin 

 stretched from these fingers over to the body in such 

 a fashion as to give them wings not unlike those of 

 the bat. In the wing of the bat, however, four of 

 the fingers of the hand run through the membrane and 

 support it. In the pterodactyl, as these flying reptiles 

 are called, the middle finger supports the web, while 

 the remaining fingers can still be used to clasp objects 

 or serve the animal to lift himself, as the bat can do 

 with his thumbs. 



Meanwhile an entire change is coming over the 

 plant world. The last third of this age of reptiles is 

 known as the Cretaceous or chalk period. Now, for 

 the first time, the forests begin to take on more of 



