180 THE OCEAN WORLD. 



To the west of the Indian Peninsula, the Maldive and Laccadive 

 Islands form the extremity of another group of atolls, and important 

 madreporic reefs, which extend towards the south, by the Maldives 

 and the Chagos Islands ; they consist of low coral formations, densely 

 clothed with cocoa-nut trees. The Maldives, the most southerly 

 cluster, include upwards of a thousand islands and reefs ; the Lacca- 

 dives, seventeen in number, are of similar origin. The Saya de Malha 

 bank, towards the south-east, constitutes a further group of madre- 

 poric islets. Finally, the coast of the Mauritius, of Madagascar, of 

 the Seychelles, and even the African continent, from the northern 

 extremity of the Mozambique Channel to the bottom of the Red Sea, 

 are studded with numerous reefs of the same nature. They fail, 

 however, almost completely, along the coast of the Asiatic continent, 

 where, among others, the waters of the Euphrates, the Indus, and the 

 Ganges, enter the sea, and diversify its inhabitants. The western 

 coast of Africa, and the east coast of the American continent, are 

 almost entirely destitute of great madreporic reefs, but they abound in 

 the Caribbean Seas. In the Gulf of Mexico, where the vast fresh- 

 water current of the Mississippi debouches into the sea, they are 

 unknown. It is principally on the north coast and upon the eastern 

 flanks of the chain of West Indian Islands that the madreporic reefs 

 show themselves in these regions. 



The polyps which have produced these vast ranges of islands 

 would be set down, at first sight, as the most incapable objects in 

 creation for accomplishing it. In the case of the Pennatulidte, the 

 case is coriaceous, strengthened with calcareous particles ; the interior 

 is a fibrous net-work containing a transparent jelly in the squares, and 

 permeated by a certain number of longitudinal cartilaginous tubes ; the 

 soft part is uniformly gelatinous, but the skin is also coriaceous, with 

 a great number of calcareous spicula placed parallel to one another, 

 adding greatly to its strength and consistency. 



The polyps are placed in this external fleshy crust ; their position 

 being marked by an orifice on the surface, distinguished by eight 

 star-like rays, which open when the upper portion of the body is forced 

 outwards, in which state it resembles a cylindrical bladder or nipple 

 crowned with a fringe of tentacula, which surround the mouth. 

 Under this orifice is the stomach, occupying the centre of the cylinder. 



