THE CHPAALOPODA 
Oo 
~ 
to 
at their cephalic extremities; they are symmetrically disposed on 
either side of the rectum (Fig. 272, 7), on the somatic wall of the 
pallial cavity, and are more or less close to the pallial aperture, 
being further from the aperture in Ommatostrephes (Oigopsida) than 
in Sepia (Myopsida). In the Decapoda Myopsida the renal orifices 
are situated on prominent papillae. 
The excretory products of the Cephalopoda consist, in part at 
least, of solid concretions, and do not contain uric acid, but chiefly 
guanin. 
The appendages of the branchial hearts of the Dibranchia (Fig. 
273, 7) correspond morphologically with the pericardial glands of 
other Mollusca. The glandular investment of the branchial hearts 
is also excretory, experi- 
GIN ment having shown that it 
plays the same physiological 
part as a pericardial gland. 
4. Nervous System.—In 
all the Cephalopoda the 
essential parts of the 
nervous system are cen- 
tralised in the head, round 
0.4 
Diagram of the coelom of a female Octopod, as seen 
from the ventral side. a.d, the so-called aquiferous 
duct; a.p, appendage of the branchial heart; b.h, 
branchial heart; ca, capsule of branchial heart; g.c, 
genital coelom (gonocoele); 0, ovary; 0.d, oviduct ; 
the initial part of the oeso- 
phagus (Fig. 271, n.c). In 
Nautilus the concentration 
of the nerve-centres is less 
than in the Dibranchia, each 
0.g, Oviducal gland; 0.0, oviducal orifice; r.p, reno- 
pericardial orifice. (After Brock.) 
pair of centres with its com- 
missure being represented 
by a ganglionic half-hoop. Of the three half-hoops forming the 
central nervous system, one, the cerebral, is dorsal, and the two others 
are continuous with it and ventral. The more anterior ventral half- 
hoop is the pedal centre, the more posterior the visceral. The pedal 
centre innervates the funnel and the circumoral appendages, the pedal 
origin of these organs being demonstrated by this innervation in 
the adult. In the female each of the two large nerves passing to 
the interior ventral series of tentacles bears a large ganglion at the 
point where it breaks up into branches to supply the supposed 
olfactory or lamellar organ (Fig. 280, z, y). The visceral centre 
gives off nerves to the mantle, the branchiae, and the viscera, the dis- 
tribution of these nerves being analogous to that of the Dibranchia 
described below. Finally, the dorsal or cerebral centre gives off nerves 
to the eyes, the otocysts, the lips, ete. A labial commissure is also 
present, arising by a double root (Fig. 279, VIII) from the cerebral 
centre and passing below the sub-radular organ; and as is the 
case in the Polyplacophora, the Aspidobranchia, and the Scaphopoda, 
the stomato-gastric commissure arises from the labial commissure in 
