imen preserved in spirits, I unfortunately
omitted to search for the vesiculae seminales; I cannot doubt that such
existed, but it would have been important to have ascertained whether
they contained spermatozoa. I made out, most distinctly, that there was
no trace of ovarian tubes within the peduncle; and my assertion may be
believed when I state, that I traced the two much finer and more
transparent cement-ducts, from the prehensile antennae up to the body of
the animal: in Lepas I have _repeatedly_ detected, with ease, the
ovarian tubes within the peduncle, before the calcification of the
valves had even commenced, and therefore at a much earlier period of
growth than in these parasites. Consequently I am prepared to affirm,
that these parasites are not females, but that, as far as can be judged,
from external organs, they are exclusively males.

_Concluding Remarks._--In comparing the capitulum of the hermaphrodite
with that of the complemental male (Pl. VI, figs. 6 and 3), we must be
struck with the differences in their shape, in the number, relative
sizes, and forms of the several valves. It should, however, be borne in
mind, that the scuta and carina in the hermaphrodite at first grow
exclusively downwards; so that if we remove the upper portions
subsequently added, the difference in shape in these valves is not so
great as it at first appears. The rostrum in the male is of much larger
relative size; whilst of the upper latera there is not a trace, although
in the hermaphrodite these valves are larger than the rostrum. The
terga, compared with those of the hermaphrodite, differ more essentially
than do the other valves; and the manner in which the primordial valves
project, shows that from the first commencement of calcification, the
lines of growth have followed an unusual course. The great breadth and
shortness of the terga is evidently related to the shortening of the
whole capitulum, and the transverse position of the orifice; and this
shortening of the capitulum, no doubt, is rendered necessary for its
reception and protection within the shallow furrow between the scuta of
the hermaphrodite. Finally, if we compare the internal parts of the
hermaphrodite and male, the differences are considerable, though partly
to be accounted for by the youth of the latter: the form and position of
the labrum, and the distance between the first and second pair of cirri,
is the same in both; but the mandibles and maxillae diff