: hence, I often
found specimens, which externally seemed to have perfected their
metamorphoses, but which, within their sacks, retained all the
characters of the natatory larva. According to Mr. King, the larva of
Lepas throws off its external shell five days after becoming attached.
Whilst the young Lepas is closely packed within the larva, the
capitulum, as known by the five valves, about equals in length the
peduncle. The peduncle occupies the anterior half of the larva; when
fully stretched, it becomes narrower and slightly longer than the
capitulum; the separation between the capitulum and peduncle is almost
arbitrary in the mature animal, and corresponds with no particular line
in the larva. Even at this early period, the muscles of the peduncle are
quite distinct. No vestige is preserved in the outer integument, of the
sternal and dorsal sutures of the larval carapace; but in the corium of
the peduncle, three coloured marks which occur near the eyes, and two
little curled marks which occur near the acoustic orifices of the larva,
are all preserved for some time after maturity. The compound eyes, as we
have seen, are attached to apodemes, springing from the sternal surface
of the larval carapace, and are consequently cast off with it: whilst
the young Cirripede is packed within the larva, the outer integument of
its peduncle necessarily forms a deep transverse fold passing over the
eyes and apodemes, and this, as we shall presently see, plays an
important part in the future position of the animal. The antennae are not
moulted with the carapace, but left cemented to the surface of
attachment; their muscles are converted into sinewy fibres, the corium
after a short period is absorbed, and they are then preserved in a
functionless condition. No trace of the two acoustic sacks can be
perceived in the corium of the young Cirripede, excepting the coloured
marks above alluded to.

In the young capitulum, the five valves stand some way apart from each
other; they are elegant objects under the microscope; they are not
calcified, but consist exclusively of chitine; they are rather thick,
composed of an outer membrane lined by hexagonal prisms, quite unlike
any other membrane in the animal. These valves, which I have called
_primordial_ valves, resemble pretty closely in shape the valves of the
mature animal; the fork of the carina, however, is indicated only by a
slight constriction above the lower end. After the exuviatio