ike the mouth in the mature animal,) certainly answers to
the mouth as made out by dissection in Scalpellum; and I believe I saw,
as has Mr. Bate, a terminal orifice: it certainly does not possess any
trophi. In Ibla (in which the larva is large enough for dissection), the
base of the proboscis arises posteriorly to the first pair of legs, and
the orifice at the other end reaches beyond or posteriorly to the point,
where the mouth in Scalpellum opens, namely between the middle pair of
legs. The mouth being either so largely probosciformed or seated only on
a slight eminence, in two genera so closely allied as Ibla and
Scalpellum, and (judging from Mr. Thompson's figures, and from what I
have seen myself,) in the species of the same genus Lepas, is a singular
difference: in the cases in which, at first, the proboscis is absent, it
would probably soon be developed. I cannot but suppose that the inwardly
directed spines on the bases of the two posterior legs, which are so
rapidly developed, serve some important end, namely, as organs of
prehension for the larvae, like the mandibles and maxillae of mature
Cirripedes, for seizing their prey, and conveying it to their moveable
mouths, conveniently seated for this purpose.

The first pair of legs answers, as I believe from reasons hereafter to
be assigned, to the outer pair of maxillipods in the higher crustacea;
and the other four legs to the first two pair of thoracic limbs in these
same crustacea; this being the case, the highly remarkable position of
the mouth in the larva, either between the bases of the two posterior
pair of legs, or at least posteriorly to the first pair, together with
the probable functions of the spiny points springing from the basal
segments of the two hinder pair of true thoracic limbs, forcibly bring
to mind the anomalous structure of the mouth being situated in the
middle of the under side of the thorax, in Limulus,--that most ancient
of crustaceans, and therefore one likely to exhibit a structure now
embryonic in other orders. I will only further remark, that I suspect
that the truncation of the anterior end of the carapace, has been
effected by the segments having been driven inwards, and consequently,
that the larger antennae within the lateral horns, though standing more
in front than the little approximate pair, are normally the posterior
of the two pair. According to Milne Edwards, the posterior pair are
normally seated outside the anterior p