ii8 I N A G U A 



forward until another wave came in. Their zone of existence 

 was bounded by the cHff tops on one side and by the roaring 

 surf on the other. They were found nowhere else on the island; 

 here they mated and deposited their eggs, found their food, 

 kept an eternal watch for their enemies, lived and died. The 

 very spirit of the surf itself, their lives were a vivid illustration 

 of how the dry barren land came first to be peopled with crawl- 

 ing animals. Where the limpets, anemones and sea urchins were 

 still completely bound to the ocean, perishing miserably of 

 heat and dryness when it left them for long, the Grapsoid crabs 

 were able to forsake it for hours at a time. Strictly speaking they 

 were still creatures of the sea, but they were also land animals 

 in process of transition. While still restricted to the twenty 

 feet bordering the area of the water's edge, they had advanced 

 further toward a life on dry land than had any of their com- 

 panions. Only an incomplete anatomical transformation from 

 gill to air-breathing lung requiring frequent wettings in the salt 

 ocean held them in place. Laboratory experiments have shown 

 that they can survive with gills completely dissected out in 

 dry air for several hours, an operation that would kill any nor- 

 mal sea-dwelling crab. 



Centipedes are noted for the amazing number of their feet. 

 But they are amateurs in the art of pedal dexterity compared 

 with the sea urchins. Sea urchins are the porcupines of marine 

 life; only a person with cast iron fingers would dare pick one 

 up, for every inch of their bodies is protected with long pointed 

 spines which are mounted in cleverly designed ball and socket 

 joints. They lived by the pool and along the cliff in great scat- 

 tered masses, giving the rocks the appearance of being festooned 

 with giant cockleburs. To fall on one would be a painful and 

 dangerous experience, for their spines are frequently very 

 poisonous, being covered with germ-filled mucus that produces 



