INTERNAL ANATOMY. Bol 
2 T. cervina, | D. rumphii | Notarchus 
Aplysiidae T. dactylom-| [= scapula] | punctatus 
Mazazarelli. ela MacF. | Amaudrut. | Vayssiére. MacF. 
Peripheral distribution. 
G1 Cul: 4 — Cal Integument between tentacles 
and rhinophores. 
a a a a | Ganglion of anterior tentacles. 
C2 C2 5 3 C2 
b b lb b | Integument and muscles of 
mouth-region. 
C3 C3 1 2 C3 Ganglion of rhinophores and ad- 
jacent integument. 
C4 C4 2 5 C4 Optic nerve. 
a | Integument and muscles of 
C5 €5 6 4 Ce5 mouth-region. On right side a 
_b | branch to the penis. 
6 Cz6 3 6 CuG Acoustic nerve. 
passes outward and forward for about 7.0 mm. and bifurcates into an inner 
and an outer ramus. The inner of these, c. 3, corresponding to the third cere- 
bral nerve of the above table, passes at once through the overlying retractor 
muscles of the head to its dorsal wall, courses forward between the eyes and 
penetrates deeply into the integument, giving off a number of fine branches and 
terminating in the ganglion of the rhinophore, at the base of the latter organ. 
The outer ramus, c. 1, the first cerebral nerve, passes forward within the cone of 
retractor muscles of the head. On the right side, just beyond its crossing above 
the superior retractor muscle of the penis-sheath, it receives an anastomosing 
branch from the third pedal nerve, which recurves posteriorly to it. A short 
distance toward the cerebral ganglion from this union a branch is given off to 
the above named muscle, seeming to be a direct continuation of the fibres from 
the pedal nerve alone. Beyond this point the main trunk of the nerve curves 
upward and is distributed to the dorsal wall of the head in front of the rhino- 
phores. 
Outside of and behind the origin of the nerve-trunk A, just described above, 
arises another nerve but slightly smaller in diameter, the second cerebral nerve. 
At a short distance from its origin it bifurcates into nearly equal rami, which 
pass downward and forward along the pharyngeal bulb. The upper of these 
