these parts serve, probably, to defend the little creature, when its eye
announces the passing shadow of some enemy, and for this purpose they
are well adapted from the extreme sharpness of the spines. The thorax,
into which I traced the vesicula seminalis, no doubt also serves for the
emission and first direction of the spermatozoa; and hence, perhaps, its
singularly extensible structure. I have already remarked, that in
specimens preserved in spirits, the thorax is often largely protruded,
and bent down at right angles to the orifice. I presume this is caused
by endosmose; nevertheless it deserves notice, that it was in these
protruded specimens that the vesicula seminalis was most conspicuously
gorged with spermatozoa. I suspect the longitudinal and transverse
muscles lining the upper part of the outer integuments of the whole
animal, can be of little use to the creature, without it be to aid in
the protrusion of the thorax, and perhaps in the violent expulsion of
the spermatozoa, thus causing them to reach the ovigerous lamellae within
the sack of the hermaphrodite. It is also probable, that the action of
the cirri of the hermaphrodite, would tend to draw inwards the
spermatozoa in the right direction. In one specimen, the spermatozoa in
the hermaphrodite and in the male were mature at the same time; in
another this was not the case; and as the males, apparently, become
attached at all periods of the year, this want of coincidence in
maturity must often occur. Can the males retain their spermatozoa, till
told by some instinct, that the ova in the sack of the often fecundated
hermaphrodite are ready for impregnation; or are the spermatozoa
sometimes wasted, as must annually happen with such incalculable
quantities of the pollen of many dioecious plants?

This little Cirripede is, in many respects, in a partially embryonic
condition. There is no separation between the capitulum and peduncle;
there is no mouth; and the thorax, throughout its whole width, opens
into the anterior part of the animal: the limbs differ greatly from
those both of the mature Cirripede and of the larva, but come closest to
the latter: the preservation of the abdomen is a well-marked embryonic
character. On the other hand, the four rudimentary calcareous valves,
the narrow orifice, the hirsute outer integument, the two muscular
layers, the single eye, and male internal organs, are all characteristic
of the fully-developed condition. The four li