76 WONDERS OF THE DEEP 



Have you ever wondered how the beautiful coral 

 reefs, of which you may have heard, have been 

 constructed ? The way in which they have been 

 formed is not at all difficult to understand. The 

 coral, while it is alive, secretes a substance called 

 carbonate of lime, and has the power of depositing 

 this chemical compound in solid masses. Now, the 

 coral polyp, instead of living inside this mass, as one 

 would expect it to do, after the manner of shell fish, 

 prefers to live outside, clothing the hard substance 

 with a kind of soft, transparent jelly. The co-opera- 

 tive principle underlies all the actions of the coral 

 polyp : they live and work together in communities, 

 and as time goes on the amount of carbonate of lime 

 secreted accumulates, and, while doing this, assumes 

 different forms, often, indeed, branching out in 

 various directions, as a tree does when it is 

 growing. 



After a time the coral polyp, having lived its 

 full term of existence, dies, and presently the soft 

 portion of the animal decomposes and is washed 

 away by the moving water, leaving behind the hard, 

 stony skeleton. Parts of this skeleton mass are 

 broken off from time to time by the currents, or 

 the waves, and the loose blocks of coral are fre- 

 quently flung with considerable force against the 

 mass, breaking off other portions, and gradually 

 grinding a great deal of this into fine coral sand, 

 which eventually fills the numerous holes and 

 crevices. In the course of a long period the whole 

 mass thus becomes cemented into hard reef rock, 



