REPORT ON SPIRULA. 
23 
The ventricle is pointed behind and in front, each point being the origin of an aorta, 
but the two aortse are not in the same line, the anterior being oblique from the outside 
towards the axis (Fig. P, vii). 
The cephalic or anterior aorta, properly so-called, is directed towards the head ; its 
distribution has not been followed in the incomplete specimen of Spirula reticulata 
examined, but in Spirula peronii a principal branch passes (as in other Cephalopods) 
between the pedal and visceral centres (PL V, fig. 4, ar.\ The short posterior aorta 
(Fig. P) gives ojff immediately to the left a recurrent branch (“anterior” aorta), which 
supplies the rectum, and at least in part the genital organs (this is a character of the 
(Egopsids, this vessel arising anteriorly and directly from the ventricle in the Myopsids ; 
the disposition observed in Spirula and the CEgopsids is evidently primitive, the parts 
supplied by this artery being morphologically posterior). It then immediately arrives 
at the shell and bifurcates, giving, on each side of the shell, a pallial branch (Fig. P, iv), 
which continues as far as the terminal disk and fins. 
The vena cava is situated quite ventrally, its terminal portion (posterior) being 
alone visible in the incomplete specimen of Spirula reticulata examined. It receives 
a trunk from the back, which traverses the bottom of the little visceral sac of the last 
chamber ; this trunk comes from the reunion of the two veins arising from the sinuses 
surrounding the stellate ganglia, veins accompanying the commissure of this last, and its 
median nerve (Fig. N, iv and ii). At the back of the anus, under the junction of the 
visceral nerves, the vena cava divides into two branches directed backwards and towards 
the sides (Fig. S) ; each of them passes into a renal sac (see further on), these 
uniting to the corresponding abdominal vein (Fig. S, vi), which presents the enlargement 
characteristic of Decapods (PI. VI. fig. 8, v.v.), then uniting further to the pallial vein (Fig. 
S, viii) in forming the branchial heart (Fig. S, vii). This last (PI. VI. hr.h. ; PI. IV. figs. 2 
and 4, hr.h.), flattened dorso-ventrally, carries a little ventral appendage directed towards 
the median line (PL VI. fig. 8, hr.app. ; Fig. S, iii), which in Spirula peronii appears 
villous (PL IV. fig. 4, a) like the pericardial gland of Nautilus, to which it morphologi- 
cally corresponds. From the branchial heart arises the afferent branchial vessel, shorter 
on the right than on the left (Fig. S, ix) and passing to the surface of the visceral sac 
on the ventral side of the oviduct (PL IV. fig. 5, hr. a.). This afferent branchial vessel 
passes to the dorsal side of the branchial axis. The branchials, situated quite laterally 
almost near the dorsal surface, have already been described (see pallial cavity). The 
efferent branchial vessels occupy the ventral side of the branchial axis ; on leaving the 
branchia, they pass before the afferent vessels which are parallel to them, then at the 
back of these last and the kidneys. That on the right side is much shorter than that on 
the left (as in Ommatostrephes, Loligo, &c., see Fig. P, i, and PL VI. fig. 8, aur. aur'.) ; it 
is also more swollen, constituting an apparent auricle, whilst to the left the branchio- 
cardiac vessel is long with a tolerably constant diameter. The two trunks, contractile in 
