32 



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 



,-v nor so important 



W 



\ ■ ■ V :' ,' " ■ I ■ ' ' '■• *£" 



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 

 and important addi- 

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

 the southern part of the mainland of Florida were so 

 formed. 



Fig. 48. — Organ Pipe "Coral" (a coralline). 



