again at the extreme end. The external membrane is very
thin, and is penetrated by the usual fine tubuli leading to the corium;
its surface is wrinkled and destitute of spines, or with extremely few.
The peduncle is often completely surrounded by a yellowish ball, (of
which I have seen specimens from the coast of England, and from off
Borneo,) sometimes half as wide as the capitulum, composed of very
tender, vesicular, structureless membrane, and of a pulpy substance:
perhaps the yellow colour may be owing to long immersion in spirits.
Some authors have supposed that the ball was the ovisac of the animal;
and for the first few minutes, deceived by the numerous included spores
of, as I believe, Bacillariae, I thought that this was the case; others
have supposed that it consisted of some encrusting algae or other foreign
organism; but it is, in reality, a most singular development of the
cement-tissue, which ordinarily serves to attach Cirripedes by their
bases to some extraneous object, but here surrounding that object and
the peduncle, gives buoyancy, by its vesicular structure, to the whole.
The membrane of the ball falls to pieces in caustic potash, differently
from the chitine membrane of the enclosed peduncle, and this shows that
there is some difference in composition from ordinary cement. The ball,
when cut in two, exhibits an obscure concentric structure. The whole is
excreted by the two cement-ducts, through two rows of orifices, one on
each side of the surrounded portion of the peduncle; and I actually
traced, in one case, the yellow pulpy substance coming out of the
cement-ducts. The upper apertures are in gradation larger than those
below them, and they stand a little further apart from each other; these
are figured as seen from the outside, much magnified, at Pl. I, fig. 6
_d_. I did not succeed in finding the cement-glands, but I followed the
ducts, of rather large size, running for a considerable distance as
usual along and within the longitudinal muscles of the peduncle. Nearly
opposite the uppermost aperture, on each side, the duct passes out
through the corium, and becomes laterally attached to the outer membrane
of the peduncle, at which point an aperture is formed (as in other
cases, by some unknown process), thus giving exit to the contents of the
duct. Beneath this upper aperture the duct runs down the peduncle,
between the corium and the outer membrane, till it comes to the next
aperture, to which it