dangerous but beautiful outgrowths of the ocean floor. 



Such a patch-work distribution seems at first sight 

 random and meaningless. The investigations of many 

 scientists over a number of years, however, have shown 

 that there is really a logical arrangement in it, and that 

 the apparent lack of order in the location of coral reefs 

 represents in reality a combination of definite require- 

 ments of the individual coral as to living conditions and 

 a very definite pattern in the distribution of these desir- 

 able conditions throughout the world. 



One of the major requirements of the reef corals is 

 that the temperature of the surrounding sea water 

 should not drop below 20° Centigrade or 70° Fahren- 

 heit by more than a few degrees or for more than a 

 short time. Prolonged exposure to slightly lower tem- 

 peratures or shorter exposure to much reduced tempera- 

 tures result in the death of reef corals. 



While some corals are perfectly capable of living 

 under conditions of sedimentation, the true reef corals 

 are easily killed by mud or sand which may settle upon 

 them in roily or still water. Corals, of the massive 

 boulder type are frequently found to be dead on the 

 upper surface where sediment naturally collects, while 

 still growing on the outer edge and sides. In extreme 

 cases this may result in the growth of a doughnut shaped 

 boulder. 



Although it is an animal, the reef coral always con- 

 tains within itself algae or small plant-like cells. Plants 

 require light in order to live and it is believed that the 

 oxygen produced by the algae k necessary for maximum 

 growth of the coral. Possibly because of this, the reef 

 corals and their contained algae are able to flourish in 

 strong sunlight only. 



i7 



