axis resuming the position of
approximate parallelism to the longitudinal axis of the whole body,
which it had in the larval condition. The reader will, perhaps,
understand what I mean, if he will look at the mature Cirripede, figured
in Pl. IX, fig. 4. In this, he will see that the body or thorax is
united to the peduncle only by a small part below the mouth; on the
other hand, if he imagines the whole bottom of the body (as high up as
the letter _h_) united and blended into the peduncle, he will see the
state in which these parts exist in the larva. Now, let him greatly
shorten the cirri, so as to resemble the natatory legs of the larva, and
then imagine a young Cirripede, with cirri _of full length_, formed
within the old one, he will see that the new thorax supporting the cirri
will have to be developed in an almost transverse position,--the animal
consequently being internally almost separated into twain.

Of the internal organs, whilst the Cirripede is still within the larva,
I have already mentioned the stomach with its pair of caeca: from the
retracted position of the thorax and rudimentary abdomen, and
consequently of the anus, compared with these parts in the larva, the
alimentary canal is not above half its former length. There is, as yet,
no trace of the filaments supposed by some to act as branchiae, at the
base of the first pair of cirri. Nor could I perceive a trace of the
testes or vesiculae seminales: the penis is represented by a minute,
apparently imperforate projection. I have already briefly described the
pair of large, gut-formed bodies in the larva, into the anterior ends of
which the cement-ducts ran, and evidently derived their slightly opaque,
cellular contents. At a very early age, before the young Cirripede can
be distinctly made out, the posterior ends of these gut-formed bodies
are absorbed, so as not to pass beyond the caeca of the stomach. When the
young Cirripede is plainly developed within the larva, these bodies in a
relatively reduced condition are still distinct near the caeca, and at
the opposite or anterior end (_i. e._ lower, in the position in which
Cirripedes are usually figured), they have branched out into a sheet of
delicate inosculating tubes; these could be traced by every stage,
until, in the young perfected Cirripede, they filled the peduncle as
ordinary ovarian tubes. In the larva, the two gut-formed bodies or
incipient ovaria keep of equal thickness from one to the othe