338 ON THE FORMATION OF CORAL ISLANDS. 



Hydra and Actinia, the tentacula are the organs of 

 feeding. 



The whole of the species of corals engaged in the 

 formation of the coral banks, are not known, hut a 

 considerable number of genera and some of the species 

 also have been ascertained. The Madreporae appear 

 to be among the most numerous ; Milleporae, Tubi- 

 porae, Caryophillese, Distichoporae, Corallinae, and 

 many more also abound ; while for these I must re- 

 fer to the works on this subject. Echini, and nu- 

 merous other shells which reside on the banks, serve 

 to augment the general mass of calcareous matter. 

 Careless observers have mistaken Holothuriae, and 

 other soft worms for the coral animals. 



It is for geography, not for a work of this nature, 

 to describe the islands and rocks produced by the 

 Coral tribes. It is here sufficient to mention the 

 islands to the south of the equator, between the west 

 coast of America and New Holland, crowding the 

 whole of that sea, under a rapid increase, accompanied 

 by still more numerous rocks, destined to become 

 the seats of vegetation, and the habitations of man ; 

 and perhaps, at length, to form a continent in the 

 Pacific ocean. To these, abounding particularly be- 

 tween New Holland, New Caledonia, and New Gui- 

 nea, I may add those of the Indian Archipelago, in- 

 cluding Cosmoledo, Chagos, Juan de Nova, Ami- 

 rante, Assumption, Cocos, and the Maldive and 

 Laccadive islands. 



When we consider the feebleness of the means 

 and the minuteness of the agents, the extent of these 

 reefs and islands is a subject of equal curiosity and 

 surprise. For these however, the reader may con- 

 sult the writings of navigators : though it will indeed 

 be sufficient to cast an eye over a map of the Pacific 



