THE CEPHALOPODA 305 
posterior part of the mantle, including the siphonal prolongation of 
Nautilus and Spirula and the fins of the various Dibranchia ; (3) a 
small genital artery, which may originate from the abdominal aorta 
(Fig. 277, g.a), or separately from the ventricle: it may even be 
triple, as in Nautilus, where there-is one artery for the gonad, one 
for its duct, and one for the homologue of the duct, the pyriform 
appendage. 
In Nautilus the circulation is partly lacunar, except in the 
integuments, but in the Dibranchia the vascular apparatus is 
remarkably perfect, and sinuses are, as a rule, absent, the blood 
passing from the arteries into the veins through the intermediary 
of capillary vessels provided with an endothelium. Nevertheless, 
7 ck : aby 
TMG Vise per: 
aperc. 
Fie. 271. 
Diagram representing an approximately median sagittal section of Sepia officinalis; this 
drawing is intended to be compared with the foregoing one. a, internal shell; a.b.v, afferent 
branchial vessel ; an, anus ; app, appendage of the branchial heart ; b, nuchal cartilage ; br.b, 
branchial heart ; c, the integument covering the visceral hump ; er, crop ; ct, the left ctenidium ; 
d, the reflected portion of the mantle-skirt forming the sac which encloses the shell; e, the 
inferior margin of the mantle-skirt ; e.b.v, efferent branchial vessel; f, the pallial chamber ; g, 
the vertically cut median portion of the funnel ; gizz, the gizzard; 7, the valve of the funnel ; 
i.s, ink-bag ; m, the two upper lobes (arms) of the foot; n, the long prehensile arms; 7.c, the 
nerve-collar ; ”.7.a, aperture of the left kidney; 0, the fifth or lowermost lobe (arm) of the 
foot ; p, the third arm; g, buccal membrane ; re, renal glandular mass ; s, the lower jaw; ¢, the 
radula; v, the upper jaw ; vent, ventricle of the heart ; visc.per.apert, viscero-pericardial aperture ; 
x, the viscero-pericardial sac. (After Lankester.) 
in the Octopoda there is a large venous sinus on the course of the 
blood returning to the gills: this sinus surrounds the oesophagus 
and salivary glands, the hepatic ducts, the anterior aorta, etc., and 
communicates by a large venous trunk with the great vena cava 
which carries to the gills the greater part of the blood coming from 
the body. In Nautilus the whole visceral cavity is a vast blood- 
sinus communicating with the vena cava by a number of perforations 
in the walls of the latter vessel, in the same manner as, in Aplysia, 
the abdominal sinus communicates with the afferent branchial vein. 
The vena cava of Cephalopods consists of a principal trunk directed 
antero-posteriorly : this trunk in Nautilus (Fig. 274, v.c) is divided 
into four, and in the Dibranchia into two afferent branchial veins, 
each of which is joined by a pallial and an abdominal vein (Fig. 
20 
