SCYPHOZOA (SEA-A^EMO^ES, CORALS, ETC.). 



All those animals which, like the sea-anemone, have an 

 oesophagus turned into the body (much as one might turn 

 in the mouth of a bag), and which have the digestive cavity, 

 subdivided by radially arranged partitions or septa, are 

 called Scyphozoa. To these characteristic features may 

 be added others. Thus there is a circle of (usually hollow) 

 tentacles surrounding the mouth, and the edges of the 

 septa bear long mesenterial filaments which are digestive 

 in function. By the septa the digestive cavity has its 

 surface greatly increased, so that the substances rendered 

 soluble by the secretions of the mesenterial filaments can 

 be more readily absorbed. Further details of structure are 

 better given in treating of the two subclasses into which 

 the Scyphozoa are divided; merely saying here that all are 

 marine. 



SUBCLASS I. ACTIKOZOA (Sea-anemones and Corals) 

 In these the animal is fixed; it never swims freely, and 

 the body in general has much the same structure as was 

 found in the sea-anemone dissected. In some the indi- 

 viduals (polyps) are separate; in others the individuals re- 

 produce by division or by budding, and the new polyps 

 thus formed never completely separate from their parents, 

 so that large aggregations or colonies result. In these one 

 can distinguish the mouths, and usually the tentacles of 

 the individual polyps, but the division does not affect the 

 digestive tract, so all are connected, and the food which is 

 taken in at one mouth may serve to nourish any part of the 



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