HYDRiE, JELLTFISHES, SEA ANEMONES, CORAL POLYPS 5b 



having vertical partitions that divide tlie lower part of the 

 hotly 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, 



mown as Metridium (Fia;. 24), will 



but a common one, ! 

 serve as an example, 

 since they are all 

 nmch alike. This one 

 is found along the 

 seacoast from Maine 

 to New .Jersey, at- 

 tached 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 expantled. 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 and has a 

 thick crown of tentacles, aii-anged around the edge, leaving 

 an open space in the miiidle, 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. 



