r specimen, masses of the most distinct spermatozoa, with the
usual little knots on them, associated with numerous cells, about as
large as and resembling those which I have examined in living
Cirripedes, and from which I have every reason to believe the
spermatozoa are developed. The vesiculae seminales unite and terminate
under the two extremely minute caudal appendages, and here I think I saw
an orifice; but there is certainly no projecting, probosciformed penis.

Having dissected the six specimens with the utmost care, and having
scrupulously examined the ovaria in other Cirripedes during their early
stages of development, even before the exuviation of the larval
locomotive organs, and in specimens of smaller size than the male Ibla,
I am prepared to assert that there are no ovaria, and that these little
creatures are exclusively males. It should be borne in mind, that in
some of the specimens there were perfect spermatozoa in the vesiculae
seminales (as likewise in some of the males of _I. quadrivalvis_), and,
therefore, if these individuals had been hermaphrodites, their ova would
have been, at this period, well developed, and ready for impregnation:
in this state it is almost impossible that they could have been
overlooked. Moreover, it is probable that such ova would not have been
very small, for the larvae whence the parasitic males are derived, attain
(as might have been inferred from the known dimensions of their
prehensile antennae, and as we shall show actually is the case in _I.
quadrivalvis_,) the size common amongst ordinary Cirripedia.

_Concluding Remarks._--That these animals are true Cirripedes, though
having so different an external appearance from others of the class,
admits of not the least doubt. The prehensile antennae, enveloped in
cement and including the two cement-ducts, would have been amply
sufficient, without other parts--for instance, the mouth, by itself
perfectly characteristic with each organ, together with the whole
alimentary canal, constructed on the normal plan,--to have proved that
they were Cirripedia. Under the head of the closely-allied _Ibla
quadrivalvis_, we shall, moreover, see that the males are
developed from larvae, having every point of structure--the peculiar
quasi-bivalve shell, the two compound eyes, the six natatory legs,
&c.,--characteristic of the Order. But in some respects, the males are
in an embryonic condition, though unquestionably mature, as shown by the
s