208 



PRACTICAL ZOOLOGY 



flowers (Fig. 124). They fasten themselves to stones, wharves, 

 and other solid objects and very seldom move when once fixed. 

 Small animals are captured by the tentacles as in Hydra and 

 carried into the mouth. 



Coral. Corals are perhaps the most interesting members of 

 the phylum Coelenterata. Coral polyps live in colonies, and 

 each member of the colony builds for itself a sort of skeleton 



FIG. 124. Sea anemones. (From Coleman.) 



out of calcium carbonate which it extracts from the water, 

 These skeletons constitute what we call coral. 



Coral polyps build fringing reefs, barrier reefs, and atolls. 

 These occur where conditions are favorable, principally in 

 tropical seas, the best known being among the Maldive Islands 

 of the Indian Ocean, the Fiji Islands of the South Pacific Ocean, 

 the Great Barrier of Australia, and in the Bahama Island 

 region. 



A fringing or shore reef is a ridge of coral built up from the 

 sea bottom so near the land that no navigable channel exists 

 between it and the shore. Frequently breaks occur in the reef, 



