he
hermaphrodite Ibla. The larvae, though not yet attached, were on the
point of attachment, so that the single eye of the mature animal could
be distinctly seen, lying near to the two great compound eyes of the
larva. We have also just seen, that one male quite recently here had
undergone its metamorphosis. The larvae are 25/1000ths of an inch in
length, and rather more than 10/1000ths in width in the widest part:
they are boat-shaped, the dorsal edge forming the keel of the boat; the
anterior end is only a little blunter than the posterior end; the
quasi-bivalve carapace is smooth. All the essential points of structure
in the larvae of other Cirripedes at this stage, could be distinctly here
seen,--such as the two compound eyes, with the apodemes to which they
are attached, and the two oblong sternal plates whence the apodemes
spring,--the adductor muscle,--the six natatory legs, with long plumose
spines,--the abdomen, with its three small segments and the caudal
appendages,--the prehensile antennae already described,--and, lastly, the
two little (auditory?) sacks at the antero-sternal edges of the
carapace, but not so near the anterior extremity as in Lepas. The four
or five larvae, after having undergone in the open sea the several
preparatory metamorphoses common to the class, must have voluntarily
entered the sack of the hermaphrodite: ultimately would they, on finding
two males already attached there, have retired, and sought another
individual less well provided; or would they all have remained, and so
formed a polyandrous establishment, such as we shall presently see
occurs sometimes in Scalpellum? This must remain quite uncertain.

In this same hermaphrodite specimen of _I. quadrivalvis_, the two
ovigerous lamellae contained some hundreds of larvae in the first stage of
development, which were liberated from their enveloping membranes by a
touch of a needle: they were about the 16/1000ths of an inch in length,
and presented all the usual characters of larvae at this period. What a
truly wonderful assemblage of beings of the same species, but how
marvellously unlike in appearance, did this individual hermaphrodite
present! We have the numerous, almost globular larvae, with lateral horns
to their carapaces, with their three pair of legs, single eye,
probosciformed mouth and long tail:--we have the somewhat larger larvae
in the last stage of development, much compressed, boat-formed, with
their two great compound