ung are passed out by the way of the mouth, and they go swimming
about as little oval bodies covered with a very curious kind of hairlike
processes. Each of these processes is capable of striking water like an
oar; and the consequence is that the young creature is propelled through
the water. So that you have the young polype floating about in this
fashion, covered by its 'vibratile cilia', as these long filaments,
which are capable of vibration are termed. And thus, although the polype
itself may be a fixed creature unable to move about, it is able to
spread its offspring over great areas. For these creatures not only
propel themselves, but while swimming about in the sea for many hours,
or perhaps days, it will be obvious that they must be carried hither and
thither by the currents of the sea, which not unfrequently move at the
rate of one or two miles an hour. Thus, in the course of a few days,
the offspring of this stationary creature may be carried to a very great
distance from its parent; and having been so carried it loses these
organs by which it is propelled, and settles down upon the bottom of the
sea and grows up again into the form and condition of its parents. So
that if you suppose a single polype of this kind settled upon the bottom
of the sea, it may by these various methods--that is to say, by cutting
itself in two, which we call "fission," or by budding; or by sending out
these swimming embryos,--multiply itself to an enormous extent, and
give rise to thousands, or millions, of progeny in a comparatively short
time; and these thousands, or millions, of progeny may cover a very
large surface of the sea bottom; in fact, you will readily perceive
that, give them time, and there is no limit to the surface which they
may cover.

Having understood thus far the general nature of these polypes, which
are the fabricators both of the red and white coral, let us consider a
little more particularly how the skeletons of the red coral and of
the white coral are formed. The red coral polype perches upon the sea
bottom, it then grows up into a sort of stem, and out of that stem there
grow branches, each of which has its own polypes; and thus you have a
kind of tree formed, every branch of the tree terminated by its polype.
It is a tree, but at the end of the branches there are open mouths of
polypes instead of flowers. Thus there is a common soft body connecting
the whole, and as it grows up the soft body deposits in i