. The
auricles, one pair, are contractile expansions of the efferent
branchial vessels. The heart gives off an anterior or cephalic and a
posterior or abdominal aorta. The vascular system is almost perfect,
arteries and veins being united by capillaries. The principal vein is
a vena cava passing backwards ventrally from the cephalic region and
dividing into two afferent branchial veins, each of which receives a
pallial and an abdominal vein. Each of these afferent branchial
vessels is enclosed in the cavity of a renal organ and is covered
externally by the glandular tissue which forms the excretory part of
the "kidney" (fig. 29). Each afferent vessel is expanded into a
contractile branchial heart, which is provided with a glandular
appendage. The latter corresponds to the glandular masses which are
attached to the afferent branchial veins in _Nautilus_, and to the
pericardial glands of other Molluscs.

[Illustration: FIG. 28.--Circulatory and excretory organs of _Sepia_
(from Gegenbaur, after John Hunter).

br, Branchiae (ctenidia).

c, Ventricle of the heart.

a, Anterior artery (aorta).

a', Posterior artery.

v, The right and left auricles (enlargements of the efferent
branchial veins).

v', Efferent branchial vein on the free face of the gill-plume.

v.c, Vena cava.

vi, vc', Afferent branchial vessels (branches of the vena cava, see
fig. 29).

vc", Abdominal veins.

x, Branchial hearts and appendages.

re, e, Glandular substance of the nephridia developed on the wall of
the great veins on their way to the gills. The arrows indicate the
direction of the blood-current.]

[Illustration: FIG. 29.--Diagram of the nephridial sacs, and the veins
which run through them, in _Sepia officinalis_ (after Vigelius). The
nephridial sacs are supposed to have their upper walls removed.

v.c, Vena cava.

r.d.v.c, Right descending branch of the same.

r.s.v.c, Left descending branch of the same.

v.b.a, Vein from the ink-bag.

v.m, Mesenteric vein.

v.g, Genital vein.

v.a.d, Right abdominal vein.

v.a.s, Left abdominal vein.

v.p.d, Right pallial vein.

v.p.s, Left pallial vein.

c.b, Branchial heart.

x, Appendage of the same.

c.v, Capsule of the branchial heart.

np, External aperture of the right nephridial sac.

y, Reno-pericardial o