52 FLORIDA REEFS. 
increase. Here, as elsewhere, destruction and construction go hand in hand, 
and the materials broken or worn away from one part of the reef help to 
build it up elsewhere. The corals forming the reef are not the only beings 
that find their home there: many other animals, — shells, worms, crabs, 
star-fishes, sea-urchins, — establish themselves upon it, work their way into 
its interstices, and seek a shelter in every little hole and cranny made by 
the irregularities of its surface. In the Zoiilogical Museum at Cambridge 
there are some large fragments of coral reef which give one a good idea of 
the populous aspect that such a reef would present, could we see it as it 
actually exists beneath the water. Some of these fragments consist of a 
succession of terraces, as it were, in which are many little miniature 
caves, where may still be seen the shells or sea-urchins which made their 
snus: and sheltered homes in these recesses of the reef 
We must not consider the reef as a solid, massive structure throughout. 
The compact kinds of corals, giving strength and solidity to the wall, may 
be compared to the larger trees in a forest, giving it shade and density ; 
but beneath these larger trees grow all kinds of trailing vines, ferns, and 
mosses, Avild-flowers, and low shrubs, filling the spaces between them with 
a thick underbrush. The coral reef also has its underbrush of the lighter, 
branching, more brittle kinds, filling its interstices, and fringing the summit 
and the sides with their delicate, graceful forms. Such an intricate under- 
brush of coral growth affords an excellent retreat for many animals that 
like its protection better than exposure 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 whicli do not contribute in any way 
to its growth, but find shelter in its crevices, or in its near neighborhood. 
But these larger animals are not the only ones that haunt the forest. 
There is a host of parasites besides, principally insects and their larvaj, 
Avhicli 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 direction, 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. 
