DWELLERS OF THE SURF 121 



larger than the entrances to their caves. These cave-dwelling 

 individuals were about as safe as it is possible to be, for they 

 were guarded by their spines and could not be approached from 

 any direction except directly in front. They paid a penalty, 

 however, for their security for they were hopeless prisoners. 

 Early in life when they had stationed themselves at some favor- 

 able spot they secreted a powerful corrosive which crumbled 

 the soft coral rock beneath them. Soon they were well out of 

 the way of the driving water, safe in their holes. But then as 

 they grew it became necessary to expand their quarters; the 

 acid and the surf etched away the walls until they fitted com- 

 fortably but the openings remained comparatively small. They 

 reminded me of those human beings who spend a lifetime carv- 

 ing niches for themselves only to find that in the end they are 

 completely enmeshed by the fruits and habits of their ambi- 

 tions. All about the pool were dozens of these imprisoned 

 urchins. They seemed as healthy and as fully formed as their 

 freer relatives. The free individuals, however, probably found 

 food more abundant, for they lived on seaweed and algae which 

 they ground up in their peculiar five -sided jaws; the prisoners 

 had to be content with whatever the passing waters brought 

 them— the inner surfaces of their dens were eaten quite clean 

 and barren. 



The sea urchins were not the only surf inhabitants who re- 

 lied on their ability to bore into the rock to protect themselves 

 from the shock of thundering waves. By lowering myself 

 slightly over the edge of the pool and into the aura of mist 

 that hung just above the tops of the bubbles I could see that 

 the coral at this point was pitted with numberless small holes. 

 Similar holes also were to be found in the shells of many of the 

 gastropods that dwelt in the area. At first scrutiny, there seemed 

 to be no life in the cavities but with a dissecting needle it was 



