that
the passage (fig. 22) from several to one segment is seen to be easily
effected. When the appendage consists of many articulations, it is
generally about as long as the pedicel of the sixth cirrus; but in _Ibla
quadrivalvis_, it is four times as long. The segments are narrow,
slightly flattened, much tapering; each (fig. 24) is surmounted by a
ring of short spines, which are generally longest on the apex of the
terminal segment. I could never trace muscles into these appendages.

_Alimentary Canal._--The oesophagus is of considerable length: it is
formed of strong, transparent, much folded membrane, continuous with the
outer integuments, and moulted with them: it is surrounded by corium,
and as already stated, by numerous muscles: at its lower end it expands
into a bell, with the edges reflexed, and sometimes sinuous: this bell
lies within the stomach, and keeps the upper broad end expanded.
According to the less or greater distance of the mouth from the adductor
muscle, the oesophagus runs in a more or less parallel course to the
abdominal surface between the first and succeeding pairs of cirri, and
enters the stomach more or less obliquely. In Ibla alone, it passes
exteriorly to, and over the adductor scutorum muscle. The stomach lies
in a much curved, almost doubled course; it is often a little
constricted where most bent; it is broadest at the upper end, and here,
in Lepas and Conchoderma, there are some deep branching caeca; in the
latter of these two genera, the whole surface is, in addition, pitted in
transverse lines. The stomach is coated by small, opaque, pulpy,
slightly arborescent glands, believed to be hepatic; these are arranged
in longitudinal lines, in all the genera, except in Alepas, in which
they are transverse and reticulated: the whole stomach is thus coated.
There is, also, a coating of excessively delicate, longitudinal and
transverse muscles without striae. The rectum varies in length, extending
inwards from the anus to between the bases of the second and fifth pair
of cirri: it is narrow, and formed of much folded transparent membrane,
resembling the oesophagus, continuous with the outer integuments, with
which it is periodically moulted. The anus is a small longitudinal slit,
in the triangular piece of membrane representing the abdomen, let in
between the last thoracic tergal arches, as already mentioned under the
head of the Metamorphoses; it lies almost between the caudal appendages,
an