THE OCEAN WORLD. 



CHAPTEE Y. 



POLYPIFEEA. 



" Happy is he who, satisfied with his humble fortune, lives contentedly in the obscure state 

 where God has placed him." RACINE. 



ENTERING on the class Polypifera, we leave the domain of the infi- 

 nitely small to enter the world of the visible. Beside the Infusoria, 

 the Polypifera, which are sometimes several inches in length, are very 

 important beings. Science has made great advances towards giving us 

 an exact knowledge of these singular animals. Many scientific pre- 

 judices have been dissipated, many errors have been corrected. The 

 Polyps, as they are denned in the actual state of Science, correspond 

 not only with the Polypes, properly so called, of Cuvier and De Blain- 

 ville, buf also with the acaleplious zoophytes of the same authors. 

 "We now know that certain Polyps engender medusw, or acalephous 

 zoophytes, and that there exist some medusae scarcely differing in their 

 structure and habits of life from the ordinary Polyps. 



Thus regarded, the Polyps comprehend a great variety of animals, 

 the bodies of which are generally soft or gelatinous substances. The 

 principal and smaller divisions, to the number of more than two, 

 are arranged round an imaginary axis, represented by the central 

 part of the body. These divisions of the body have in their ensemble 

 the appearance of a regular cylinder, of a truncated cone, or of a 

 disk. They are invested with a skin or envelope of calcareous or 

 siliceous corpuscles, and even a portion of the deepest-lying tissues 

 may be invaded by a calcareous deposit, the mass of which belongs some- 

 times to an individual ; sometimes it is common to many, constituting 

 what Dr. Johnston calls the Polypidom, of which Professor Grant 



