[2], Cement-ducts and one cement-gland of [Chelonobia patula],
represented without the basal membrane, to which they
adhere:
f, f, main cement-trunk;
g, enlarged portion;
h, gland;
a, b, the two ducts proceeding from this gland,
and bifurcating several times before debouching on the
under side of the basal membrane. Several other cement-ducts,
proceeding from other glands, are represented just
as they appeared under the microscope.
[3], Cement-ducts and glands of [Tubicinella trachealis], represented
without the basal membrane to which they adhered:
(f) (f), main cement-trunk, connecting the several
glands;
h, cement-gland;
a, cement-duct, with a singular loop (a′) having two
projections or rudimentary branches;
b, spur or rudiment of a second cement-duct; c, third
cement-duct.
[4 a], Chain of cement-glands of [Balanus tintinnabulum], with all
the ducts removed, excepting those proceeding from the
last formed gland, which latter correspond in age with the
last-formed zone of the shelly basis; the whole of the basis
having been removed by acid.
f, main cement-trunk connecting the glands.
gh, last-formed cement-gland.
k, t, two cement-ducts, proceeding from a great common duct;
one of these bifurcates at (t), and one branch joins at (t′)
the corresponding branch from the corresponding gland.
i i i, circumferential duct, into which the ducts k, k, t, t, t′ all
enter.
i′ i′, branches proceeding from the circumferential duct, which
branch and sub-branch till they form a sheet (z z) of
cement-tissue on the outside of the basis of the shell.
[4 b], two cement-glands of [Bal. tintinnabulum] (this figure, to match
with 4 a, ought to have stood upside down), taken from
near the centre of the basis, greatly enlarged;
(f f), main trunk;
(g), enlarged portion of the trunk;
(h), gland;
k, t, two cement-ducts proceeding from a common point, one of
them (t) bifurcates, and gives off a rudimentary branch, t′;
m, a spur, or rudimentary duct.
The gland, h, has been
pushed on one side, it ought to lie over the enlarged
portion (g). There is a considerable difference between
these two glands and that (gh) represented in fig. 4 a; the
neck of the gland in the latter being elongated into a great
common duct, and the spur or rudimentary duct (m) being
absent.
a, b, flexor and extensor muscles, moving the upper segment
(i to k) of the pedicel.
c and d, flexor and extensor muscles, apparently moving the
lower segments of both rami, as a whole; the lower articulations
in these rami being confluent.
e and f, flexor and extensor muscles extending up both rami
(those only in the near ramus being figured) to their tips.
gg, flexors of the separate segments in both rami.
h, basal articulation of lower segment of the pedicel.
i, upper articulation of lower segment of the pedicel.
k, upper articulation of upper segment of pedicel.
[8], Larva of Scalpellum vulgare, immediately after coming out of
the egg, seen on the ventral surface (letters of reference
given below).
[9], Larva of [Balanus balanoides], immediately after coming out of
the egg, seen on the ventral surface, copied from Mr. C.
Spence Bate’s drawing in ‘Annals and Magazine of Natural
History’ (S. 2), vol. viii, Plate VI, fig. 1 (letters of
reference given below).
[10], Larva of [Chthamalus stellatus], after the first moult, but
during the first stage, seen on the ventral surface, copied;
with some alterations, from Mr. C. Spence Bate’s drawing
in ‘Annals and Magazine of Natural History’ (2 Ser.),
vol. viii, Plate VIII, fig. 13.
(The following letters apply to above figs. 8, 9, 10.)
a, eye.
b, first pair of antennæ, not observed in fig. 9.
b′, the same antennæ, as yet encased (in fig. 8) within small
horns.
c, horns, including the second pair of antennæ.
d, mouth, probosciformed: in fig. 8, the specimen having
been acted on by potash, the œsophagus can be seen
within, with the orifice beneath the swelling, which
latter perhaps answers to the labrum.
e, first, uniramous natatory leg (homologically the second
thoracic limb).
fg, second and third, biramous natatory legs (homologically
the third and fourth thoracic limbs.)
h, posterior point of carapace.
i, forked terminal projection of the body or abdomen.
l, second forked projection.
m, two sharp points, apparently representing a third forked
projection.
n, a rounded swelling, apparently lying between the carapace
and the supposed abdomen, and believed to form the
anus.
PLATE [30.] LARVÆ OF LEPAS: SECOND AND LAST STAGES OF DEVELOPMENT.
Fig. [1], Larva of Lepas in the second stage of development;
a, supposed antennæ (second pair);
m, mouth;
c, three pairs of legs. (Copied from Burmeister’s
‘Naturgeschichte der Rankenfüsser,’ Tab. 1, fig. 3.)
[2], Lepas australis: pupa or larva (2 a, of natural size) in the last
stage of development, with the young cirripede in its natural
position, obscurely seen within,—the specimen
having been treated with caustic potash, and so rendered
transparent,—viewed laterally and greatly enlarged.
Scarcely more than the outline of the shell or carapace is
represented. The darkly shaded part to the left represents
the extent of the sack of the pupa, or the cavity occupied
by the thorax, with its limbs.
a, both antennæ, adhering by their discs to a piece of wood.
b, dorsal surface of the shell or carapace; and immediately underneath
this letter is the point of reflection of the membrane
investing the thorax, so as to line the sack of the pupa.
b′, is the posterior end of the animal, and of the orifice on the
ventral surface, through which the legs are protruded.
c, six pairs of natatory legs.
d, pair of caudal appendages, seated on a minute abdomen.
m, mouth, from which the œsophagus can be seen running into
the stomach, the latter having two dark cæca; the stomach
sweeps round in the pupa to the abdomen, near b′;
but in the young included cirripede, only as far as the
letter (b), where the bases of the posterior pair of cirri and
the anus lie.
n, apodemes, supporting the eyes, produced deeply inwards
from the eye-bearing segment (N, in fig. 4) of the antennæ.
s, bottom of sack of the young cirripede immediately after its
metamorphosis; it extends as far as s′. (See s, in fig. 3.)
t, gut-formed cement-gland (or incipient ovaria), seen on the
near side of the animal, whence a cement-duct, t′, runs
into the near antenna.
u, internal and anterior part of the pupa, filled with pulpy, oily
matter, together with the incipient muscles of the peduncle;
when stretched out it forms the peduncle of the
young cirripede. See u′, in fig. 3.