Chap. 23 COELENTERATES — SIMPLE MULTICELLULAR ANIMALS 



491 



Fig. 23.20. Upper, the edge of the Great Barrier Reef and the overwash of the 

 sea at Heron Island, Australia. The Great Barrier Reef is 1350 miles long and in 

 places 30 miles wide. It is a natural factory where billions of coral animals take 

 lime from the sea water and build the cups that protect them and bury their an- 

 cestors. Lower, corals on the Great Barrier Reef at South Malle, Australia. (Cour- 

 tesy, Australian News and Information Bureau.) 



