a i 
NERVOUS SYSTEM OF MOLLUSKS. 353 
di sabi and they evidently 
correspond, both in 
‘position and functions, to the sensory ganglia of higher ani- 
tals, whilst the posterior gan- 
-glion has for its offica to regulats 
the respiratory movements. In 
the Pecten, however, as in other . 
Conchifera which possess a 
foot (fig. 62), we find an addi- 
tional ganglion (c), the pedal, 
connected with the cephalic 
ganglia, and sending nerve- 
trunks to that organ. There 
‘is good reason to believe that, 
whilst the cephalic ganglia alone 
are the instruments of sensation, 
‘so that they exert a general 
to the reflex actions 
_ 438. A similar arrangement is 
mnd in the higher Mollusks, 
ong which the ganglia are more 
3 merous, in accordance with the 
“greater variety of functions to be 
‘we find the cephalic ganglia rising 
higher and higher on the sides of 
the cesophagus ; and in the Aplysia 
they meet on the central line above 
it, forming the single mass (a, fig. 
183), which receives the nerves of 
the eyes, tentacula, &c., and sends 
Branches of communication to the 
Other ganglia. The branches which 
. ‘ser ds backwards are three on each 
AA 
NENG Z 
WAS 
~\ 
mtrol and direction over the Fig- 182.—Nz=nvous System or Pecrex. 
ements of the animal, th halic ganglia; B, branchial 
and Gemcbicd aateian “engin G ganglion; Pen 
: 433) of the organs which they supply. 
Fig. 183.—Nznvovus System oF 
APLYSIA. 
