CCELENTERATA — CORALS 



123 



Florida to Cape Cod ; it does not occur in the colder water 

 north of the Cape. 



Each polyp, glassy white and translucent in appearance, con- 

 sists of a barrel-shaped body, averaging 3 mm. wide by 9 mm. 



Fig. 46. — The common coral, Astrangia dance (x 12), from Long Island Sound, 

 showing a polyp in feeding position upon the calcareous, cuplike base {cu.), also 

 (at left) the coral portion of a bud without its secreting polyp, col., the spongy 

 pseudo-columella ; cu., the cuplike calcareous base secreted by the polyp; cu' ., 

 part of the cup sectioned transversely ; dig., digestive cavity, — the entire interior 

 of the barrel-shaped body; me., mesenteries; mo., mouth; ne., clusters of nettle- 

 cells, by means of the poison in which the prey is paralyzed; a\, oesophagus; 

 s., septa (which alternate with the mesenteries) ; /., tentacles (one is partly dissected 

 to show that its hollow interior is continuous with the large digestive cavity of the 

 polyp). 



high when fully expanded, with a circle of 18 to 24 long, tapering 

 tentacles surrounding the top. At the center of the top and 

 slightly raised is the oval mouth ; this leads through a short 



