ran up between them.

I may here state, that I found on one Scalpellum, three males very
lately attached, and not as yet imbedded in the chitine border; they
were white, opaque, pulpy, and full of oily globules; the lower part was
considerably more pointed, and extended further beyond the prehensile
antennae, than in the older and imbedded specimens. There were distinct
remnants of two great reddish-brown eyes, showing that in this respect
the larvae of the male in their last stage of development, are
characterised like the larvae of other Lepadidae. The male larva would,
probably, be a little larger than the male itself; but yet compared with
the larva in the earliest stage, there can have been unusually little
increase of size during the several intermediate metamorphoses; I judge
of this from the dimensions of the larva of the hermaphrodite in the
first stage, namely, 9/400ths of an inch, exactly the size of some of
the smaller males. In the allied genus Ibla, the increase is also less
than is usual, namely, from 15/1000ths of an inch, the diameter of the
ovum, to only 25/1000ths of an inch, the length of the boat-shaped
larva, just before its final metamorphosis.

_Habits and Concluding Remarks._--The males are imbedded in the spinose
chitine border of the occludent margin of the scuta, exactly over an
oblique fold or notch (fig. 15 _a_ _a_), close by the umbo. This fold
has no direct relation to the males, but being present is taken
advantage of by them; for it occurs in the young hermaphrodite, before
the attachment of the males, and in species of the genus in which the
males are attached to other parts. It occurs, also, in fossil species of
Pollicipes, and in these it seems caused by the upper inner part of the
valve being rendered more and more prominent during growth: in the
present species, I suspect, its origin is connected with the formation
of a ridge bounding the outer side of the pit for the adductor scutorum
muscle: we shall see in the next species, that this fold is of the
highest importance in relation to the position of the Males. The
transparent chitine border of the scuta is broad, and fills up the fold
in the shell, so that the outline of the occludent margin is not
affected by it: in the drawing (fig. 9) some of the inner layers of
chitine (_e_ _e_), which dipped into and filled up the fold, have been
removed, that the lower part of the animal might be more plainly
exhibited. The chitine bears n