and ordinary form of Ibla. The full importance of the
above generic resemblance in the antennae, will hereafter be more clearly
seen, when their classificatory value is shown in the final discussion
on the sexual relations of Ibla and Scalpellum.

Here, then, we have a pedunculated Cirripede _very much_ nearer in all
its essential characters to Ibla than to any other genus, and
exclusively of the male sex; and this Cirripede in six specimens, from
two distant localities, adhered to an Ibla exclusively of the female
sex. May we not, then, safely conclude that these parasites are the
males of the _Ibla Cumingii_? Considering that, in the same class with
the Cirripedia, there is a whole family of crustaceans, the Lerneidae, in
which the males, compared with the females to which they cling, differ
as much in appearance as in Ibla, and are even relatively smaller, I
should not have added another remark, had there not been under the head
of the following species, and of the next genus Scalpellum, a class of
allied facts to be advanced, which in some respects support the view
here taken, but in others are so remarkable and so hard to be believed,
that I will call attention to the alternative, if the above view be
rejected. The ordinary _Ibla Cumingii_ must have a male, for that it is
not an hermaphrodite can hardly be questioned, seeing how easy it always
is to detect the male organs of generation; and we must consequently
believe in the visits of a locomotive male, though the existence of a
locomotive Cirripede is improbable in the highest degree. Again, as the
little animal, considered by me to be the male of _I. Cumingii_, is
exclusively a male, (for there were no traces of ova or ovaria, though
the spermatozoa were perfect,) we must believe in a locomotive Cirripede
of the opposite sex, though the existence in any class of a female
visiting a fixed male is unknown:[48] in short, we should have
hypothetically to make two locomotive Cirripedes, which, in all
probability, would differ as much from their fixed opposite sexes, as
does the Cirripede, considered by me to be the male of _I. Cumingii_,
from the ordinary form. This being the case, I conclude that the
evidence is amply sufficient to prove that the little parasitic
Cirripede here described, is the male of _Ibla Cumingii_.

[48] It deserves notice, that in the class Crustacea, both in the
Lerneidae and in the Cirripedia, the males more closely resemble
the l