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 
