238 RADIATES: POLYPS. 



is an opening called the mouth, and around the mouth 

 are one or more rows of hollow feelers, or tentacles. 

 The mouth opens directly into an inner sack, which is 

 the stomach, and this stomach opens at the bottom into 

 the main body. The main body is divided by parti- 

 tions, which run from the bottom to the top, and from 

 the outer wall to the stomach. Through the opening 

 at the bottom of the stomach there is free communi- 

 cation with all the chambers formed by the partitions, 

 and these chambers connect with the tentacles ; so that 

 the food, after being digested, passes into the main 

 body, and thence into the tentacles, thus nourishing 

 every part. The food of polyps consists of small ma- 

 rine animals of various kinds, which are secured by 

 means of the tentacles and the curious and wonderful 

 lassos situated on the tentacles, and the nature of which 

 has already been described on page 229. The word 

 Polyp means many-footed, and is given to these ani- 

 mals on account of their numerous tentacles ; but it 

 must not be supposed that the latter are feet in any 

 true sense. Most kinds of polyps are attached to the 

 rocks, shells, or other bodies beneath the waves. Some 

 live singly, others in communities whose numbers are 

 often far more numerous than the leaves upon the 

 trees. Polyps increase by means of eggs, by budding 

 in a manner much like that of trees and shrubs, and 

 by division of one animal into two or more, so that the 

 largest communities arise from a single animal. The 

 eggs are formed on the vertical partitions, and pass 

 out, through the mouth, into the water. When first 

 hatched the young do not look like the parent, but are 

 little oval bodies which move freely about by means of 

 the fringe-like appendages, called vibratile cilia, with 



