MANUAL OF NATUKAL HISTORY. 353 



are especially the animals that propagate their kind 

 upon the crests of mountain-ranges under the sea, 

 on the tops of submarine hills, or round the margins 

 of the craters of submerged volcanoes, forming, by 

 their gradual growth and decay, those "atolls/" 

 barrier-reefs, and coral-islands, met with so abun- 

 dantly in the great Pacific Ocean. The Actinic® 

 are isolated, fleshy polyps, attached to marine 

 bodies by their bases, and with their mouths sur- 

 rounded with numerous coloured tentacles, which 

 give them, when expanded, the appearance of ani- 

 mal-flowers ; hence they have been named " Sea 

 Anemones/' The red coral of commerce (Coral- 

 Hum rubrum) is obtained principally from the 

 Mediterranean, about the islands of Majorca and 

 Minorca ; it is also procured from the Coast of 

 Africa. The Corallines of Linnaeus are cellular in 

 their microscopic character, and although they re- 

 semble the skeletons of polyps, yet belong to the 

 Vegetable Kingdom. 



VI. CLASS.— POLYPS (Polypifera). 



Animal with a circle of retractile, non-ciliated 

 tentacles surrounding the mouth ; stomach simple, 

 with a single orifice ; gemmiparous and oviparous. 



I. OEDEE.— Hydroid-Polyps (Hydroida). 



Polyps compound, rarely single and naked ; ten- 

 tacles filiform, roughish ; stomach without proper 

 parietes ; reproductive gemmules pullulating from 

 the body, and naked or contained in external ve- 



