THE CCELENTERATES 43 



Nearly all species, like the sea-anemones, are brilliantly 

 colored during life, and several are highly phosphorescent. 

 All are marine, and while they are found everywhere, from 

 the shore-line to great depths, the more abundant and 

 larger species inhabit the clear, warm waters of the tropics 

 down to a depth of one hundred and sixty feet. In such 

 regions the stag-horn corals especially grow in the wildest 

 profusion, and become tall and greatly branched. Except 

 in quiet water they are continually being broken by the 

 waves, beaten into fragments, and the resulting sand is 

 deposited about their bases. As a result of this continu- 

 ous growth and erosion, there have been formed from coral 

 sand mixed with the shells of mollusks and the skeletons 

 of various Protozoa several of the islands along the Florida 

 coast and many of those of the Pacific, some of them 

 hundreds of miles in extent. 



