48 A NOVICE IN THE ANDAMANS 



animals, or polyps," having a strong family resem- 

 blance to the familiar sea-anemone, and that a coral- 

 reef is a mass of rock gradually built up in the main 

 by the continuous budding and branching and dying 

 down of many different species of coral-polyps. 



If the reader will imagine a scrub jungle on a very 

 gently sloping incline, in which the spaces between 

 the various kinds of bushes gradually become filled 

 up, partly by the increase in size of the bushes 

 themselves, and partly by all sorts of litter from the 

 branches and their inhabitants, until at last the jungle 

 is a solid mass of dead wood with only the outermost 

 twigs still living and growing in the fresh open air, 

 he will have some sort of idea of the way in which 

 a coral-reef is formed. 



It must not be supposed that all the different 

 kinds of coral-polyps burgeon and branch like shrubs, 

 or that all take part in forming coral-reefs. Some 

 species live a solitary life, or at most grow out into 

 small plots or encrusting patches, and such ''solitary" 

 corals have been found in all seas and at all depths 

 up to nearly 3000 fathoms. The reef-making corals, 

 however, are found at the present day only in tropical 

 and subtropical seas, and there they can exist only 

 in the warm, shallow water, from high-water mark 

 down to about 30, or exceptionally 50, fathoms. 



Coral-reefs occur in three principal forms : as fringing 

 reefs close to shore, and in part laid bare at ordinary 



