CHAPTER LXIX 



PROTECTIVE ACTIVITIES 



411. Home-making. When the earthworm burrows into 

 the ground, it thus escapes the birds and other enemies ; but 

 the burrowing is essentially a process of food getting, for the 



animal feeds by 

 swallowing dirt as 

 it digs along, and 

 absorbing from it 

 organic material 

 left by decaying 

 plant and animal 

 matter. In the 

 same way, the 

 larva? of various 

 insects and many 

 adult beetles es- 

 cape their ene- 

 mies by boring 

 into trees. 



In the simplest 

 of animals, where 

 all the activities 

 of life center in 

 the protoplasm of 

 a single cell, the 

 movements related to protection or escape from injury are hardly 

 to be distinguished from the activities related to the getting of 

 food. The simple life will cover all of its necessities by a few 

 acts. But with higher animals it is often difficult to draw a 



368 



Fig. 1S6. The piddock 



This mollusk grinds its way into the rock, growing larger as it 

 digs deeper, so that in the end it is completely imprisoned 



