488 EVOLUTION OF ANIMALS Part V 



liantly colored fishes. Probably no place on earth is so replete with life as the 

 undersea gardens of coral reefs. All of these plants and animals leave their 

 remains on the coral and gradually build it up toward the surface where it then 

 receives the drift brought by winds and waves. 



Coral Reefs. There are three main types of coral reefs and they are among 

 the most interesting of land masses (Fig. 23.19). A fringing reef is near the 

 coast, separated from it only by narrow strips of shallow water. It is a platform 

 of coral which projects outward from the shore and ends steeply on the sea- 

 ward side of the reef. Breaks occur here and there in the reef, letting currents 

 into the shallows, but little or no navigation is possible. Barrier reefs resemble 

 the fringing ones but differ in that there are wide, deep channels between the 

 mainland and the reef. The world famous one is the Great Barrier Reef of 

 Australia (Fig. 23.20). The atoll is a ring-like reef with an opening in one or 

 several places into a lagoon which may be less than a mile or as much as 50 



Fig. 23.17. Snake-locks anemone (Anemonia sulcate). The tentacles and cilia 

 bring food to the central mouth. No garden is more beautiful than are colonies of 

 sea anemones — ivory, yellow, purple, rust-colored, and orange, with their trans- 

 lucent tentacles shifting and stretching in the currents. (Photograph courtesy, 

 Douglas P. Wilson, Marine Biological Laboratory, Plymouth, England.) 



