ANIMAL BIOLOGY 



coating has apertures through which the polyps pro- 

 trude in order to feed when no danger is near (Fig. 46). 



FIG. 46. RED CORAL- 

 LINE with crust and 

 polyps (eight tentacles). 



FIG. 47. SEA FAN (a coralline). 



The red " corals " used for jewelry are bits of stalks of cor- 

 allines. The corallines (Figs. 47, 48) are not so abundant 



nor so important 

 as the coral polyps 

 (Figs. 45, 49). 



Colonies of coral 

 polyps grow in 

 countless numbers 

 in the tropical seas. 

 The coral formed 

 by successive colo- 

 nies of polyps accu- 

 mulates and builds 

 up many islands 



FIG. 48.-ORGAN PIPE "Coral" (a coralline). and im p O rtant addi- 



tions to continents. The Florida "keys," or islands, and 

 the southern part of the mainland of Florida were so 

 formed. 



