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 14 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 
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Fig. 24.—Sea anemones (the two upper ae and malas 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, 
