218 ZOOLOGY 
of cartilage is in the head. Here there is a cephalic cartilage 
of complicated form, which is pierced by the oesophagus. It 
ensheaths the chief nerve ganglia, the ear is embedded in 
it, and it forms two recesses which lodge the eyes. Another 
portion affords some support to the bases of the arms, and there 
is also a flat piece situated in the neck known as the nuchal 
plate. 
The chief nerve ganglia are aggregated round the oeso- 
phagus, close behind the buccal mass, and are embedded in the 
Fic. 128.—Lateral view of the nervous centres 
and nerves of the right side of Octopus vul- 
garis. From a drawing by A. G. Bourne. 
After Lankester — Zoological Articles re- 
printed from the Hncyclopedia Britannica. 
Cerebral ganglion, 
The optic nerve. 
Pedal ganglion giving nerves to arms. 
Pleuro-visceral ganglion. 
Right visceral nerve. 
Right stellate ganglion of the mantle, con- 
nected by a nerve to the pleural portion 
of 4. 
Branchial branch of 5, 
8. Olfactory branch of 5. 
9. Buecal ganglion. 
10. Buccal mass. 
SNS Co a 
> 
cartilaginous skeleton. The cerebral ganglion on the dorsal 
side of the oesophagus gives off a pair of nerves which end in 
the superior buccal ganglion, from which a pair pass to 
the inferior buccal ganglion, both lying on the surface of the 
buccal mass. In connection with these ganglia there is a well- 
developed stomatogastric system. lLaterally each cerebral 
ganglion is continued into two very stout optic nerves ; 
these expand into the optic ganglia, situated at the back 
of the eye. 
The cerebral ganglion gives off two circum-oesophageal com- 
missures, which pass down to the nervous mass on the ventral 
surface of the oesophagus. This mass is composed of three 
ganglia very much fused together. Anteriorly le the pedal 
