)
(FIGURE 57. Pupa of a Balanide (Chthamalus ?), magnified 50 diam. The
adherent feet are retracted within the rather opaque anterior part of
the shell.
FIGURE 58. Pupa of Sacculina purpurea, magnified 180 diam. The filaments
on the adherent feet may be the commencements of the future roots.)
Notwithstanding their agreement in this important peculiarity, the
Nauplii of these two orders present material differences in many other
particulars. The abdomen of the young Cirripede is produced beneath the
anus into a long tail-like appendage which is furcate at the extremity,
and over the anus there is a second long, spine-like process; the
abdomen in the Rhizocephala terminates in two short points,--in a
"moveable caudal fork, as in the Rotatoria," (O. Schmidt). The young
Cirripedes have a mouth, stomach, intestine, and anus, and their two
posterior pairs of limbs are beset with multifarious teeth, setae, and
hooks, which certainly assist in the inception of nourishment. All this
is wanting in the young Rhizocephala. The Nauplii of the Cirripedia have
to undergo several moults whilst in that form; the Nauplii of the
Rhizocephala, being astomatous, cannot of course live long as Nauplii,
and in the course of only a few days they become transformed into
equally astomatous "pupae," as Darwin calls them.
The carapace folds itself together, so that the little animal acquires
the aspect of a bivalve shell, the foremost limbs become transformed
into very peculiar adherent feet ("prehensile antennae," Darwin), and
the two following pairs are cast off; like the frontal horns.
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