[7], [Balanus amaryllis]: maxilla on twice the scale of the mandible
and palpus;
b, upper free segment;
b′, apodeme;
b1, thickened portion of membrane, perhaps answering
to the second segment of the mandibles;
b2, thin membrane, extending down to the basal edge of the mouth,
possibly answering to the basal segment of the mandibles;
or perhaps the thickened membrane forming the protuberance
c2 in fig. 3, may be considered as the basal
segment of the maxillæ.
u, step-formed projection at lower angle of maxilla.
[8], Thorax of [Coronula diadema]: outer membrane of the five posterior
segments laid almost flat, and viewed externally as a
transparent object.
2 to 6, the second to the sixth cirrus, cut off a little above
their basal articulations.
a, basal curved end of the probosciformed penis.
b, anus;
b′, the membrane surrounding the anus, probably
consisting of a rudiment of the abdomen.
c, rectum, seen through on the under side.
d, basal articulation of the sixth cirrus;
d′, do. of the fifth cirrus;
d2, do. of the second cirrus.
e e′, posterior thoracic segment, carrying the sixth pair of
cirri; the dorso-lateral portion e is separated, in this one
segment, from the corresponding portion e′ by a narrow
slip of thinner membrane, which may be a part of the
abdomen let in.
e2 e2, thoracic segment, supporting the second pair of cirri.
f, f3, folds or articulations between the adjoining segments.
g, swollen, punctured portions of membrane, not differing
homologically from the rest of the segments.
h, posterior portion of the prosoma, or the specially enlarged
part of the thorax; it carries the first pair of cirri; homologically
h forms part of the second segment of the
thorax of the archetype Crustacean.
A, infra-œsophageal ganglion; two pairs of rather small nerves,
arising from the dorsal surface, cannot be here shown.
B, supra-œsophageal ganglion, double.
C, ophthalmic ganglion, single.
D D, eyes, as believed to exist.
a, three pairs of nerves, running to the gnathites and olfactory
pouches;
a′, nerve rising from the collar, running towards the mandibles.
b, single medial nerve, running to the great transverse
muscle, extending across the upper part of the stomach.
c, collar-nerve or chord, uniting the infra- and supra-œsophageal
ganglions.
d, great splanchnic nerve, here spread laterally out, but
properly running along the sides of the upper part of
the prosoma, and therefore under the collar-nerve;
d′, plexus by which this nerve is connected with the
supra-splanchnic nerve, e.
e, supra-splanchnic nerve, rising from the collar, almost in
contact with the supra-œsophageal ganglion;
e′, small nerve rising from the end of the supra-œsophageal
ganglion, and running to the adductor and surrounding muscles.
f, f, pair of great nerves (antennular), distributed over the
sack and shell.
g, chord (in appearance single), uniting the supra-œsophageal
ganglion with the first (C), or ophthalmic ganglion.
h, small medial nerve, running to near the adductor muscle.
i, nerve supposed to run from the ophthalmic ganglion to the
eye.
k, small nerve, rising from the main ganglion (A), between
r1 and r2, or the nerves running to the first and second
pairs of cirri.
œ, position of the œsophagus.
r1 nerve entering the first cirrus.
r2, r3, r4, r5, r6, nerves entering the five succeeding
pairs of cirri.
Fig. [1 a], Basal membrane, with the cementing apparatus, of [Coronula
balænaris]; a small portion of the parietal membrane, p p p,
which coats the folded shelly walls, is left adherent to the
basal membrane.
b, the circumferential slip (shaded more darkly than the rest to
catch the eye), separating the basal from the parietal membrane.
c′ c′, slips of basal membrane, formed at each period of growth,
and overlapping each other.
s s s s s s, the six sutures in the walls, separating the six compartments,
of which—
A is the basal margin of the rostrum,
C C that of the lateral compartments,
D D that of the carino-lateral compartments, and
E that of the carina.
r, r, rays or spokes of membrane, prolonged from the circumferential
slip, and running under the trebly folded wall of
each compartment, but here cut off; a similar ray should
run under each line of suture (s). These rays, at their
extremities, expand transversely; and the shape and length
of the rays may be judged of from the basal outline of the
folded walls given in Pl. 16, fig. 5.
The two cement-ducts, proceeding from each cement-gland,
debouch opposite the middle folds of the lateral (C C) and
carino-lateral (D D) compartments. The layers of cement
have been removed. N.B. There is one considerable error
in this figure, the two main trunks, connecting the cement-glands,
and meeting at the centre, have been represented as
forming a straight line, but in fact they form a very open
angle, as is correctly shown in fig. 1 c.
[1 b], Diagram, representing a vertical section through a portion of
the basal and parietal membranes, with the thickness of
the membrane enormously exaggerated.
z z z, layers of cement, which, if the section had been made in
the line of the cement-ducts, would have been seen proceeding
out of these ducts, as is represented at (t), where
the section is supposed to have taken the above course.
c′ c′, the slips of basal membrane.
b, the circumferential slip; beneath this the coarsely dotted
layer represents the cement, lately excreted, and before it
has acquired its proper transparent structureless character,
elsewhere represented by fine dots.
p, membrane externally coating the walls of the shell.
t, cement-ducts opening beneath the basal membrane.
[1 c], The central portion of fig. 1 a, considerably magnified.
c′ c′, slips of the basal membrane; but the shell, when these
were formed, was so young that the walls had not acquired
their folded structure; in the centre the prehensile antennæ
of the pupa may be obscurely seen.
f, the main cement-trunk, connecting the cement-glands.
h, a cement-gland, from which two cement-ducts proceed.
a a, cement-ducts (cut off), leading to opposite the middle fold
of the carino-lateral compartment.
b b, cement-ducts (cut off), leading to opposite the middle fold
of the lateral compartment.
a′ b′, a pair of cement-ducts, with their orifices opening on the
under side of one of the slips of basal membrane (c′), at a
point which once was opposite the middle of the carino-lateral
and lateral compartments. The orifices of the other
ducts, towards the centre, may be seen forming straight lines.