THE CEPHALOPODA 315 
are united by a thin supra-oesophageal commissure in the adult. 
The pedal centres proper supply nerves chiefly to the funnel, and 
thus correspond to the dorsal moieties of the pedal cords of 
Rhipidoglossa which innervate the epipodium; but they also send 
fibres to the brachial nerves, and therefore, in conjunction with 
the brachial ganglia, control the locomotory functions. 
The pleural centres lie on the sides of the posterior part of 
the sub-oesophageal mass; they are but little differentiated and 
scarcely visible externally, and they give off the two great pallial 
nerves (Fig. 281, pl). The visceral 
centres are situated on the ventral Vy / 
side of the mass, and give off the 
large visceral nerves, which arise 
separately in Spirula and the 
Octopoda, but are more or less 
fused at their origin in Ommato- 
strephes, Sepia, ete. The pallial 
or ‘‘stellate” ganglia (Fig. 281, 
gang.stell) are secondary centres 
on the course of the pallial nerves, 
and are situated on the internal 
wall of the mantle near its an- 
terior or dorsal border. ‘These 
ganglia are connected by a trans- fy 
verse supra-oesophageal commis- |_--7.v08¢. 
sure, which is slender and is y 
formed by the union of the two , 
; , Ss gang, stell. | 
nerves of the pallial siphon in ey Z 
Spirula, is larger in sundry other X. 47 /\ 
Oigopsida (Ommatostrephes, Ony- 
F ; nor 
choteuthis, Enoploteuthis, Gonatus, 
Veranya, Thysanoteuthis), is re- CED” 
duced in Loligo, and is absent in Walp A 
the adult Sepiola. This commis- 
sure, together with the two fused } 
: : Lateral view of the nervous centres and 
nerves of the pallial siphon of nerves of the right side of Octopus vulgaris. 
Yen 4 ‘ way, 0.9, buccal ganglion; cer, cerebral ganglion ; 
Spu ula, repl esents the two primi gang.stell, the right ‘‘stellate” pallial gan- 
tive pallial nerves and is the glion ; n.br, branchial nerve ; 7.0lf, its supposed 
’ ; olfactory branch; w#.visc, the right visceral 
homologue of the pallial cords, nerve; ped, pedal ganglion; pl, pleural 
: : ganglion ; wisc, visceral ganglion. (After Lan- 
united by a commissure dorsad {esier.) 
of the intestine, of Amphineura ; 
whereas the large pallial nerves of the Dibranchia are neogenetic 
structures, evoked by the great development of the mantle 
borders, which are reflected over and finally enclose the shell, 
and give rise to the fins, ete. In some cases the-visceral nerves 
are also united by a commissure in the form of a transverse 
Fic. 281. 
