178 AGE OF CORAL REEFS. 
mit and the sides with their delicate, graceful 
forms. Such an intricate underbrush of Coral 
growth affords an excellent retreat for many 
animals that like its protection better than ex- 
posure to the open sea, just as many land-animals 
prefer the close and shaded woods to the open 
plain. A forest is not more thickly peopled with 
Birds, Squirrels, Martens, and the like, than is 
the Coral Reef with a variety of animals which 
do not contribute in any way to its growth, but 
find shelter in its crevices, or in its near neigh- 
borhood. ¢ 
But these larger animals are not the only ones 
that haunt the forest. There is a host of parasites 
besides, principally Insects and their larve, which 
bore their way into the very heart of the tree, 
making their home in the bark and pith, and not 
the less numerous because hidden from sight. 
These also have their counterparts in the Reef, 
where numbers of boring Shells and marine 
Worms work their way into the solid substance 
of the wall, piercing it with holes in every direc- 
tion, till large portions become insecure, and the 
next storm suffices to break off the fragments so 
loosened. Once detached, they are tossed about 
in the water, crumbled into Coral sand, crushed, 
often ground to powder by the friction of the 
rocks and the constant action of the sea. 
After a time, an immense quantity of such 
