Fig. 1, Nervous system of _Coronula diadema_, seen from the
ventral surface.
A, infra-œsophageal ganglion; two pairs of rather small
nerves, arising from the dorsal surface, cannot be here
shown.
B, supra-œsophageal ganglion, double.
C, ophthalmic ganglion, single.
D D, eyes, as believed to exist.
_a_, three pairs of nerves, running to the gnathites and
olfactory pouches;
_a′_, nerve rising from the collar, running towards the
mandibles.
_b_, single medial nerve, running to the great transverse
muscle, extending across the upper part of the stomach.
_c_, collar-nerve or chord, uniting the infra- and
supra-œsophageal ganglions.
_d_, great splanchnic nerve, here spread laterally out, but
properly running along the sides of the upper part of the
prosoma, and therefore under the collar-nerve;
_d′_, plexus by which this nerve is connected with the
supra-splanchnic nerve, _e_.
_e_, supra-splanchnic nerve, rising from the collar, almost
in contact with the supra-œsophageal ganglion;
_e′_, small nerve rising from the end of the supra-œsophageal
ganglion, and running to the adductor and surrounding
muscles.
_f_, _f_, pair of great nerves (_antennular_), distributed
over the sack and shell.
_g_, chord (in appearance single), uniting the
supra-œsophageal ganglion with the first (C), or ophthalmic
ganglion.
_h_, small medial nerve, running to near the adductor muscle.
_i_, nerve supposed to run from the ophthalmic ganglion to
the eye.
_k_, small nerve, rising from the main ganglion (A), between
_r^1_ and _r^2_, or the nerves running to the first and
second pairs of cirri.
_œ_, position of the œsophagus.
_r^1_ nerve entering the first cirrus.
_r^2_, _r^3_, _r^4_, _r^5_, _r^6_, nerves entering the five
succeeding pairs of cirri.
_s_, nerve entering the probosciformed penis.
2, nervous system of _Balanus tintinnabulum_; letters of
reference as in fig. 1.
3, acoustic sack of _Balanus tintinnabulum_.
4, " " _Coronula diadema_.
5, eye of _Balanus tintinnabulum_; _i_, nerve coming from the
ophthalmic ganglion; D, eye itself.