CCELENTERA TES. 



39 



of it settles down among the corals and converts the reef into a solid mass. 

 Little by little the accumulation goes on, the waves constantly throwing 

 the sand inward, until at last a firm land is obtained, upon which plants 

 becin to grow and animals to live. 



The distribution of the coral islands on the face of the globe seems 

 most capricious, and still it is to be explained by the direction of the pre- 

 vailing currents. In the western Pacific coral islands are most numerous : 

 next comes the Caribbean Sea, in which the Bahamas are the largest exam- 

 ples of purely coral islands and reefs. There are also extensive banks in 

 the Indian Ocean, as around Mauritius, Madagascar, and at the entrance 

 to the Red Sea. They are almost entirely lacking from the western shore 

 of Africa and from the eastern shore of South America, as well as the 

 whole western shore of both Americas. 



