5386 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
ventral pair posterior to these, which give oft the visceral 
nerves (fig. 70, Ant. Vise. G. and Vise. G.). 
Commissures.—Short stout commissures connect the 
sub- and supra-oesophageal nerve masses. ‘There are two 
such pairs, the posterior being the broader:—(1) the 
anterior pair, uniting the cerebral and brachial ganglia, 
and (2) the posterior pair, uniting the cerebral and 
viscero-pedal masses. 
NERVES. 
From the brain are given off numerous pairs of 
nerves, which innervate the different regions of the body. 
A. The nerves given off from the cerebral ganglia 
are:—(1) Optic, (2) olfactory, (3) labial (4 pairs), (4) 
buccal, (5) anterior superior ophthalmic nérves, and the 
motor nerves of the eyeball. 
B. The nerves given off from the sub-oesophageal © 
mass are :—(1) Posterior superior ophthalmic, (2) inferior 
ophthalmic, and the motor nerves of the eyeball, (3) 
anterior infundibular, (4) posterior infundibular, (5) 
visceral, (6) pallial, (7) accessory pallial, (8) anterior 
vena caval, (9) auditory, (10) brachial, (11) interbrachial, 
and (12) the nerves of the head. 
A. (1) The Optic nerves are stout, rather short 
nerves running straight out from the lateral region of the 
cerebral ganglion at the level of the posterior groove 
(fig. 70, Opt. V.). In section the optic nerve is oval, 
and piercing the cranial cartilage it enters the orbit 
and there expands into a large oval optic ganglion from 
which are given off nerves to the retina (Pl. IX, fig. 71, 
R.N.). These optic ganglia are each greater in bulk 
than the two supra-oesophageal ganglia, and are about 
twice as long as they are thick. Internal to the optic 
ganglion, on the dorsal side of the optic nerve, is a much 
