420 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
the sense cells. The pallial muscles are also innervated 
by branches from the circumpallial nerve. The circum- 
pallial nerve is connected with both the cerebro-pleural 
and visceral ganglia; with the former by the anterior 
pallial nerves (V. pa.) already described (figs. 16 and 18, 
NV. pall.). 
The pallial nerves from the visceral ganglion do not 
pursue a similar course on the right and left sides of the 
body. On the right, that is, the side on which the gill is 
attached to the mantle, the palhal nerves pass out as a 
large trunk very close to the branchial nerve, and run 
alongside this until the point is reached where the 
branchial nerve enters the gill lamellae. 
Here they enter the mantle, and at once divide into 
branches which radiate out to the circumpallial nerve 
(fig. 3, MW. pall.). The main branch, however, passes 
along in the mantle, after bending sharply, exactly in the 
line of attachment of the basal gill lamellae, and from 
this the various branches arise. 
On the left side the distribution is somewhat different. 
The pallial nerves are not collected to form a large trunk, 
but radiate out directly from the ganglion over the surface 
of the adductor muscle until the mantle is reached; 
entering the mantle, they pass out, branching on the way, 
to the circumpallial nerve. In all probability these 
pallial nerves also innervate the pallial muscles. There 
are, in addition to the pallial nerves already described, 
certain nerves which leave the visceral ganglia from the 
posterior angles of the lateral lobes, and pass directly back 
over the surface of the adductor until they reach and enter 
the mantle opposite the terminal point of attachment of 
the rectum (fig. 28, V. pp.). 
With regard to the histology of the visceral ganglion, 
the ganglion cells are, for the most part, grouped over the 
