THE CONQUEST OF THE DRY LAND 227 



enough by eating the soil for the sake of the 

 plant remains in it, and by collecting plant 

 crumbs on the surface. The more they 

 worked, age after age, the more soil they 

 made, and the more plants there were with 

 crumbs to eat. In their newly discovered 



FIG. 28. DIAGRAM OF SOME BURROWERS. 



An Earthworm to the right, a Mole-cricket to the left, a Mole 



in the middle. 



country below the ground the earthworms 

 lived, if not in ease, at least in safety. Mean- 

 while, however, evolution was in progress. 

 The second great invasion of the dry land had 

 occurred, which led on to creatures like centi- 

 pedes and burrowing, carnivorous beetles, both 



