that of the branches, is solidified by the
deposition of carbonate of lime in its tissue, somewhat in the same
fashion as our own bones are formed of animal matter impregnated with
lime salts; and it is this dense skeleton (usually turned red by a
peculiar colouring matter) cleared of the soft animal investment, as
the hard wood of a tree might be stripped of its bark, which is the red
coral.

In the case of the red coral, the hard skeleton belongs to the interior
of the stem and branches only; but in the commoner white corals, each
polype has a complete skeleton of its own. These polypes are sometimes
solitary, in which case the whole skeleton is represented by a single
cup, with partitions radiating from its centre to its circumference.
When the polypes formed by budding or division remain associated, the
polypidom is sometimes made up of nothing but an aggregation of these
cups, while at other times the cups are at once separated and held
together, by an intermediate substance, which represents the branches
of the red coral. The red coral polype again is a comparatively rare
animal, inhabiting a limited area, the skeleton of which has but a very
insignificant mass; while the white corals are very common, occur
in almost all seas, and form skeletons which are sometimes extremely
massive.

With a very few exceptions, both the red and the white coral polypes
are, in their adult state, firmly adherent to the sea-bottom; nor do
their buds naturally become detached and locomotive. But, in addition to
budding and division, these creatures possess the more ordinary methods
of multiplication; and, at particular seasons, they give rise to
numerous eggs of minute size. Within these eggs the young are formed,
and they leave the egg in a condition which has no sort of resemblance
to the perfect animal. It is, in fact, a minute oval body, many hundred
times smaller than the full grown creature, and it swims about with
great activity by the help of multitudes of little hair-like filaments,
called cilia, with which its body is covered. These cilia all lash the
water in one direction, and so drive the little body along as if it were
propelled by thousands of extremely minute paddles. After enjoying its
freedom for a longer or shorter time, and being carried either by the
force of its own cilia, or by currents which bear it along, the embryo
coral settles down to the bottom, loses its cilia, and becomes fixed to
the rock, gradually