mains is carried to the sea floor,
even to great depths; but the main dependence of the deep-sea forms of
animals is upon other animal forms, which themselves may have obtained
their store from yet others. In fact, in any deep-sea form we might
find it necessary to trace back the food by thousands of steps before
we found the creature which had access to the vegetable matter. It is
easy to see how such conditions profoundly limit the development of
organic being in the abysm of the ocean.

The sedentary animals, or those which are fixed to the sea bottom--a
group which includes the larger part of the marine species--have to
depend for their sustenance on the movement of the water which passes
their station. If the seas were perfectly still, none of these
creatures except the most minute could be fed; therefore the currents
of the ocean go far by their speed to determine the rate at which life
may flourish. At great depths, as we have seen, these movements are
practically limited to that which is caused by the slow movement which
the tide brings about. The amount of this motion is proportional to
the depth of the sea; in the deeper parts, it carries the water to and
fro twice each day for the distance of about two hundred and fifty
feet. In the shallower water this motion increases in proportion to
the shoaling, and in the regions near the shores the currents of the
sea which, except the massive drift from the poles, do not usually
touch the bottom, begin to have their influence. Where the water is
less than a hundred feet in depth, each wave contributes to the
movement, which attains its maximum near the shore, where every surge
sweeps the water rapidly to and fro. It is in this surge belt, where
the waves are broken, that marine animals are best provided with food,
and it is here that their growth is most rapid. If the student will
obtain a pint of water from the surf, he will find that it is clouded
by fragments of organic matter, the quantity in a pound of the fluid
often amounting to the fiftieth part of its weight. He will thus
perceive that along the shore line, though the provision of victuals
is most abundant, the store is made from the animals and plants which
are ground up in the mill. In a word, while the coast is a place of
rapid growth, it is also a region of rapid destruction; only in the
case of the coral animals, which associate their bodies with a number
of myriads in large and elaborately organized com