THE INVERTEBRATES 137 



wall a stony skeleton of carbonate of lime which persists 

 after the polyp is dead. We know these animals chiefly 

 by their skeletons, which we see in masses in collections, 

 or made into ornaments. But in tropical oceans there are 

 whole islands of coral, or long coral reefs fringing the shores 

 of continents, formed by the skeletons of millions of polyps. 

 For as they live closely massed together in great colonies 

 their skeletons form solid stony banks. Coral islands have 

 a great variety of form, but the elongated, circular, ring- 

 shaped, and crescent forms predominate. In the Atlantic 

 Ocean they are found along the coasts of Southern Florida, 

 Brazil, and the West Indies; in the Pacific and Indian 

 oceans there are great coral reefs on the coasts of Australia, 

 Madagascar, and elsewhere; and certain large groups of 

 inhabited islands, as the Fiji, Society, and Friendly Islands 

 are almost exclusively of coral formation. 



There are over 2000 kinds of coral polyps known, and 

 their skeletons vary much in appearance. Because of the 

 suggestive appearance of some of these they have received 

 common names, as the organ-pipe coral, brain coral, etc. 

 The red coral of which jewelry is made grows chiefly in the 

 Mediterranean Sea. It is gathered specially on the western 

 coast of Italy, and on the coasts of Sicily and Sardinia. 

 Most of this coral is sent to Naples, where it is cut into orna- 

 ments. 



By walking along the sea-beach soon after a storm one 

 may find many shapeless masses of a clear and jelly-like 

 substance scattered here and there on the sand. These 

 are the bodies or parts of bodies of jellyfishes which have 

 been cast up by the waves. Exposed to the sun and wind 

 they soon die or evaporate away to a small shrivelled mass. 

 The flesh of a jellyfish contains hardly more than one per 

 cent of solid matter, all the rest of it being water. 



Jellyfishes, although closely related to the fixed polyps, 

 some indeed being the immediate offspring of them, have 



