166 THE OCEAN WORLD. 



divided into thirteen provinces, named atollons, which is so far a 

 natural division in that place, that each atollon is separated from the 

 other, and contains a great number of smaller islands. It is a marvel 

 to see each of these atollons surrounded on all sides hy a great hank 

 of stone walls such as no human hands could huild on the space of 

 earth allotted to them. These atollons are almost round, or rather 

 oval, heing each ahout thirty leagues in circumference, some a little 

 less, others a little more, and all ranging from north to south, without 

 any one touching the other. There is between them sea channels, one 

 broad, the other narrow. Being in the middle of an atollon, you see 

 all around you this great stone bank, which surrounds and protects 

 the island from the waves ; but it is a formidable attempt, even for 

 the boldest, to approach the bank and watch the waves as they roll in 

 and break with fury upon the shore." 



Since the publication of Laval's description, many circular isles, or 

 groups of islands, analogous to these atollons, since called atolls > have 

 been discovered in the Pacific Ocean and other seas. The naturalist 

 Forster, who accompanied Cook in his voyage round the world, first 

 made known the more remarkable characteristics of these gigantic for- 

 mations. He perfectly comprehended their origin, which he was the 

 first to attribute to the development of the calcareous zoophytic 

 polypier. 



After Forster, many other naturalists Lamouroux, Chamisso, Quoy, 

 Gaimard, Ehrenberg, Ellis, Darwin, Couthony, and Dana have fur- 

 nished Science with many precious lessons on the natural history of 

 coral islands and madreporic reefs. We can only glance at a few 'of 

 the more remarkable genera of these interesting creatures. 



" Those occupying the same Coral," says Fredol, " live in perfect 

 harmony ; they constitute a family of brothers, physically united in 

 the closest bonds of union. They occupy the same dwelling, each 

 having its separate chamber ; but the power of abandoning it is 

 denied them. Attached each to its cell, they are driven to trust in 

 Providence for the food which never fails them ; moreover, what is 

 eaten by each mouth profits the whole community. Urged on by a 

 wonderful instinct, the polypes labour together at the same work ; 

 isolated, they would be weak and helpless ; in combination, they are 

 strong." M. Lacaze-Duthiers has even demonstrated that Antipatlies 

 ylaberrima, Gorgonia tiiberculata (Lamarck), Leiopatlies glabemma 



