IIYDR^I*:, JELLYFISHES, SEA ANEMONES, CORAL TOLYl'S 5o 



having vertical partitions that divide the lower part of the 

 body into distinct compartments. In these two respects 

 the Actinozoa show a decided advance over the Hydrozoa 

 and the Scyphozoa. 



Sea anemone. — There are many species of sea anemones, 

 but a common one, known as Metridium (Fig. 24), will 

 serve as an example, 

 since they are all 

 much alike. This one 

 is found along the 

 seacoast from Maine 

 to New Jersey, at- 

 tachetl to piles of 

 bridges, rocks, or 

 sunken timbers. Me- 

 tridium has a soft, 

 leathery, cylindrical 

 body, varying from 

 three to eight inches 

 in diameter, when 

 fully expanded. At 

 the base, this cylinder 

 is slightly expanded to 

 form a large sucker, 

 by means of which the animal attaches itself. The free 

 end of the body is covered by a membrane antl has a 

 thick crown of tentacles, arranged around the edge, leaving 

 an open space in the middle, in the center of which is an 

 aperture, the mouth. This opens directly into the gullet, 

 which is an oval sack suspended from the membrane cover- 

 ing the end of the body. The gullet opens below into the 

 stomach, or body cavity. The gullet does not hang freely 



Fig. 24. — Sea anemone. 



