as I have shown, a pouch, certainly
serving for some sense, I believe for hearing, is seated in quite a
different position at the anterior end of the carapace. I may mention
that I found sessile Cirripedes very sensitive of vibrations in objects
adjoining them, though not, apparently, of noises in the air or water.
In a group of specimens, I could not touch one even most delicately
with a needle, without all the adjoining ones instantly withdrawing
their cirri; it made no difference if the one touched had its operculum
already closed and motionless.

_Reproductive System_,--_Male Organs._--All the Cirripedia which I have
hitherto examined, with the exception of certain species of Ibla and
Scalpellum, are hermaphrodite or bisexual.[17] I shall so fully describe
the sexual relations of the several species of these two genera, under
their respective headings, and at the end of the genus of Scalpellum,
that I will not here give even an abstract of the grounds on which my
firm belief is based, that the masculine power of certain hermaphrodite
species of Ibla and Scalpellum, is rendered more efficient by certain
parasitic males, which, from their not pairing, as in all hitherto known
cases, with females, but with hermaphrodites, I have designated
_Complemental Males_.

[17] I am compelled to differ greatly from the account given by
Prof. Steenstrup of the reproductive system in the Cirripedia, in
his 'Untersuchungen ueber das Vorkommen des Hermaphroditismus, ch.
v, 1846;--a translation of which I have seen, owing to the great
kindness of Mr. Busk. Mr. Goodsir has described ('Edin. New Phil.
Journal,' July 1843,) what he considers the male of Balanus; but
I have seen this same parasitic creature charged with ova,
including larvae! From the resemblance of the larvae to the little
crustacean described by Mr. Goodsir, in the same paper, as a
distinct parasite, I believe the latter to be the male of his
so-called male Balanus, and that all belong to the same species,
allied to Bopyrus. This genus, as is well known, is parasitic on
other crustacea; and it is a rather interesting fact thus to
find, that this new parasite which is allied to Bopyrus, in
structure, is likewise allied to it in habits, living attached to
Cirripedia, a sub-class of the crustacea.

The male organs have been well described by M. Martin St. Ange, whose
observations have since been confirmed by R. Wagner.[18