14 MR GOODCHILD ON 
bered that in the adult state the coral animal is fixed, and 
can no more roam abroad in search of food than can an 
oyster. What food it gets has to be brought to it by the 
waves of the sea. On the seaward side of a coral reef there 
are myriads of tiny mouths waiting to be filled by whatever ” 
suitable food may come along. To enable the coral animal 
to secure some of this food, it is provided with special organs 
which enable it to shoot out stinging threads at any animal 
desirable for food which may be brought within reach by the 
waves. By this means the prey is paralysed, and is then 
transferred by means of the tentacles to the mouth. Sea- 
water on the outer margin of a reef is usually full of minute 
creatures suitable for the food of the coral animal; but a 
reef is often very wide, and is, moreover, tenanted not only by 
corals of very many kinds—reef-building corals, and various 
other corals, both simple and compound—but also by great 
mumbers of species of worms, echinoderms, crustacea, 
molluses, ete., all of whom are more or less dependent upon 
their food-supplies being brought to them by the waves. It 
follows from this that millions of hungry beings are waiting 
to be fed over every superficial yard of the coral reef, and 
are ready to intercept anything good that the waves may 
bring their way. It thus becomes a case of “ first come, first 
served.” The animals on the seaward margin of the reef get 
the best and the most of the food-supply, and by the time 
the waves have traversed the reef for even a short distance, 
most of the food has been intercepted, and there is often not 
enough left for those farther from the sea to enable them to 
thrive. Thus those inland die, and those on the seaward 
margin increase and multiply apace. The increase takes 
place by a process of repeated bedding and branching, by 
which the more vigorous corals push their way out to sea; 
while the. multiplication, which goes on concurrently with the 
extension of the coral branches, arises from the vast numbers 
of ova which go forth from the parent stocks into the sea. 
Reef-building corals cannot live above high-water mark ; 
they are limited in their downward extension by the depth to 
which the required temperature happens to exist; they die and 
their hard parts are dissolved away from the surface downward 
in the central and older-formed parts of the reef; and they both 
