380 THE BOTWM OF THE SEA. 



INFLUENCE OF LIFE ON VARIATIONS IN THE BED 

 OF THE OCEAN. 



1. Formation of Coral Reefs; limit to their growth — Conditions 

 favourable to their development. 



Animal and vegetable life influences to a great extent 

 the various changes at the bottom of the sea. We 

 have already seen that animals of the smallest size 

 build the most important submarine constructions, 

 but that every other kind of existence has also a hand 

 in this continual transformation or modification of the 

 submarine world. 



The tropical seas especially swarm with an immense 

 variety of living beings. But as in other seas, so here 

 in warmer waters, the shores are more inhabited than 

 the deeps, and at a little distance from the surface 

 life ceases to exist. 



We will attempt to describe briefly one of the most 

 interesting and wonderful of marine phenomena, that 

 of the construction of coral reefs, ^^ hich attain such 

 important dimensions in the Pacific Ocean, the Indian 

 Ocean, and the West Indian seas. 



