ds the front and back of the mouth. The horny plates
grow from a fibrous and vascular matrix, which covers the palatal
surface of the maxillae, and sends out plate-like processes, one of
which penetrates the base of each blade. Moreover, the free edges of
these processes are covered with long vascular thread-like papillae,
one of which forms the central axis of each of the hair-like fibres
mainly composing the blade. A transverse section of fresh whalebone
shows that it is made up of numbers of these soft vascular papillae,
circular in outline, and surrounded by concentrically arranged
epidermic cells, the whole bound together by other epidermic cells,
that constitute the smooth (so-called "enamel") surface of the blade,
which, disintegrating at the free edge, allows the individual fibres
to become loose and assume a hair-like appearance.

Whalebone really consists of modified papillae of the mucous membrane
of the mouth, with an excessive and horny epithelial development. The
blades are supported and bound together for a certain distance from
their base, by a mass of less hardened epithelium, secreted by the
surface of the palatal membrane or matrix of the whalebone in the
intervals of the plate-like processes. This is the "gum" of the
whalers. Whalebone varies much in colour in different species; in some
it is almost jet black, in others slate colour, horn colour, yellow,
or even creamy-white. In some descriptions the blades are variegated
with longitudinal stripes of different hues. It differs also greatly
in other respects, being short, thick, coarse, and stiff in some
cases, and greatly elongated and highly elastic in those species in
which it has attained its fullest development. Its function is to
strain the water from the small marine molluscs, crustaceans, or fish
upon which the whales subsist. In feeding, whales fill the immense
mouth with water containing shoals of these small creatures, and then,
on closing the jaws and raising the tongue, so as to diminish the
cavity of the mouth, the water streams out through the narrow
intervals between the hairy fringe of the whalebone blades, and
escapes through the lips, leaving the living prey to be swallowed.

Although sometimes divided into two families, _Balaenidae_ and
_Balaenopteridae_, whalebone-whales are best included in a single
family group under the former name. The typical members of thi