rifice placing the left renal sac or nephridium
in communication with the viscero-pericardial sac, the course of
which below the nephridial sac is indicated by dotted lines.

y', The similar orifice of the right side.

a.r, Glandular renal outgrowths.

w.k, Viscero-pericardial sac (dotted outline).]

_Coelom._--The coelom forms a large sac with a constriction between
the anterior or pericardial division and the posterior or genital
division, and it is produced into lateral diverticula which contain
the branchial hearts; but in the Octopoda the pericardial division is
suppressed and the genital division communicates by long ducts with
sacs containing the appendages of the branchial hearts. The renal sacs
communicate with the pericardium by pores near the external renal
apertures; in the Octopoda the reno-pericardial openings are in the
capsules of the branchial hearts. The genital ducts pass from the
genital coelom to the exterior. They are paired in female Oigopsida
and Octopoda except _Cirrhoteuthidae_, but only the left persists in
the males of all Dibranchiata, and in the female Myopsida.

[Illustration: FIGS. 30, 31.--Nerve-centres of _Octopus_. Figure 30
gives a view from the dorsal aspect, figure 31 one from the ventral
aspect.

buc, The buccal mass.

ped, Pedal ganglion.

opt, Optic ganglion.

cer, Cerebral ganglion.

pl, Pleural ganglion.

visc, Visceral ganglion.

oes, Oesophagus.

f, Foramen in the nerve-mass formed by pedal, pleural and visceral
ganglion-pairs, traversed by a blood-vessel.]

In the oviduct is a glandular enlargement, and in addition to this the
females are provided with the so-called nidamental glands which are
developed on the somatic wall of the pallial cavity, one on each side
of the rectum, except in certain Oigopsida (_Enoploteuthis, Cranchia,
Leachia_) and in the Octopoda, in which these organs are absent. The
latter fact is related to the habit of the majority of the Octopoda of
guarding or "incubating" their eggs, which have little protective
covering. In the other cases the eggs are surrounded by a tough
gelatinous elastic material secreted by the nidamental glands.

[Illustration: FIG. 32.--Lateral view of the nervous centres and
nerves of the right side of _Octopus vulgaris_ (from a drawing by A.G.
Bourne).

bg, Buccal ganglion.

cer, Cerebral