CG5LENTERATA ACTINOZOA. 



125 



in the Polyzoa. The individual members of these colonies 

 are called polypes (Gr. polus, many; pous, foot) ; the 

 entire colony, the actinosoma (Gr. aktis, a ray; soma, a 

 body); the common fleshy structure, the ccenosarc (Gr. 

 koinos, common; sarx, flesh). The corals are fixed; the 

 sea-anemones are capable of shifting their position very 

 slowly; the Ctenopkora can swim with facility by the 

 action of their 

 cilia. The sea-ane- 

 niones and Cteno- 

 pliora are destitute 

 of any hard struc- 

 ture. Some groups 

 secrete a horny, 

 others a calcareous 

 skeleton, which 

 is called coral. 



180. The com- 

 mon sea-anemone 

 (actinia) forms a 

 good example of 

 this class. It is a 

 simple animal, the 

 actinosoma consist- 

 ing of a single po- 

 lype. It may be 

 found on the sea 

 shore, in almost any 

 rocky pool. When 

 the tide is out, it 

 looks like a little 

 lump of red flesh; 

 but, when it gets 

 covered with sea 

 water,its true shape soon appears. It is of a cylindrical 

 form, and is firmly, but not permanently, attached to a 

 rock by its lower part or base, which acts like a sucker. 

 It is able to move along, at the rate of a few inches a 



Fra 62. SEA-ANEJIOXE, 

 attached to a gasteropod shell. 



