40 



ANIMAL FORMS 



40. Sea-anemones. In its external appearance the sea- 

 anemone (Fig. 24) bears some resemblance to the Hydra, but 

 is of a much larger size (1 to 45 c.m., or \ inch to 1-J feet 

 in diameter), and is frequently brilliantly colored. The 

 number of tentacles is also more numerous, and the mouth 

 leads into the body by means of a slender esophagus (Fig. 

 25). Numerous partitions from the body wall extend in- 

 ward, and many unite to the esophagus, keeping the latter 



FIG. 24. Sea anemones (the two upper figures) and solitary coral polyps. 



in position. Below the esophagus each partition projects 

 into the great cavity of the body and bears upon its inner 

 free edge several important structures. The first of these, 

 known as the mesenteric filaments (Fig. 25), appearing like 

 delicate frills, plays an active part in the digestion of the 

 food. Associated with these are long, slender threads, 



