168 
THE OCEAN WORLD. 
into thirteen provinces, named atollons, which is so far a natural divi- 
sion 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 by a great bank of stone — 
walls such as no human hands could build on the space of earth allotted 
to them. These atollons are almost round, or rather oval, being each about 
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 fuiy 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 zoophytie 
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 polypier,” 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 lor the food which never fails thorn ; 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 Anlipcdhes 
glaberrima, Gorgonia tuberculata (Lamarck), Leiopathes glaberrinid 
