$ 209. THE CEPHALOPHORA. 235 
5. With other Apneusta, the oesophageal ring is composed of several 
contiguous ganglia which closely bind the cesophagus, but have no appar- 
ent commissures. 
6. The other Gasteropoda, and especially the Pectinibranchia and 
Pulmonata, have a highly-developed superior and inferior ganglionic mass ; 
the ocsophageal ring is formed by these ganglia, being connected on each 
side by a cord, which is oftener double than single. The superior mass 
is composed usually of two ganglia which are connected by a transverse 
commissure, or are contiguous, and sometimes even blended together. 
The inferior mass also presents many variations. With some species it 
consists of a circle of distinct ganglia, connected by commissures;“" while 
with others, it is composed of a group of ganglia more or less fused 
together. 
§ 209. 
With many of the Cephalophora,® there is a Splanchnic nervous system. 
This can be divided into a Plexus splanchnicus anterior and posterior. 
The first is composed usually of a double Ganglion pharyngeum inferius, 
connected by a transverse commissure, or contiguous, but rarely blended 
together. They are situated under the csophagus and connect with the 
cerebral mass by two filaments; they send off nerves principally to the 
pharynx, to the esophagus and the salivary glands; and when the posterior 
plexus is wanting, they send nerves also to the liver and the genital glands.” 
7 This ph 1 ring is d of eight gan- 
glia with Tergipes (Nordmann, loc. cit. p. 35, 
Tab. II.), but with Actaeon, there are only seven, 
the lower one of which, asymmetrical, sends two 
very long cords of communication to two large 
cerebral ganglia, while the two lateral ganglia con- 
nect by a short commissure passing under the 
esophagus (Aliman, loc. cit. p. 194, Pl. VII. fig. 
1. According to a communication which Kélliker 
has made to me, this ring, with Flabedlina, has 
only five ganglia. 
’ 8 See Berthold, in Miller’s Arch. 1836, p. 378. 
9 There is a transversal commissure between the 
two cerebra] ganglia with Patella, Haliotis, Pha- 
sianella, Janthina, Turbo, Paludina, Lymna- 
eus, Planorbis, and with many other species having 
a shell. These two. ganglia are contiguous with 
Helix, Limaz, and Cypraea; but they are fused 
into one with Buccinum, Murex, Oliva, Harpa, 
Voluta, and other Pectinibranchia. 
10 Haliotis has two, and Patella four inferior 
ganglia disposed transversely, which send off 
from each side a double cord of communication to 
the brain. With Ancylus, Lymnaeus, Planor- 
bis, Physa, Succinea, Bulimus, the inferior por- 
tion is composed of five to seven ganglia, unequal and 
disposed asymmetrically, and d together by 
commissures 3 see Berthold, loc. cit.,and my ob- 
servations in Wiegmann’s Arch. 1841, I. p. 153, 
Taf. VI. fig.3 (Lymnaeus stagnalis). Judging 
from the figure of Van Beneden (Exercices zoot. 
loc. cit. Fasc. I. Mém. sur le Lymnaeus gluti- 
nosus, p. 30, Pl. I. fig. 12, and: Ann. d. Sc. Nat. 
VII. 1837, p. 112, Pl. ITI. B.), of the oesophageal 
ring of Amphipeplea, this genus resembles, in this 
respect, Lymnaeus. ith Pneumodermon vio- 
laceum (Van Beneden, loc. cit. p. 45, Pl. I. fig. 2), 
and with Clio (Eschricht, loc. cit. p. 6, Tab. IL. 
fig. 28), the lower portion appears also to consist 
of a circle of ganglia. 
ll Heliz, Limaz, Arion. With Limaxr (Pou- 
chet, Recherch. loc. cit. p. 8), there remains in the 
middle of the fused ganglia only a small opening, 
which, with several species of Heliz, entirely disap~ 
pears.* 
1 See Brandt, Ueber der Mundmagennerven der 
Evertebraten, loc. cit. p. 43. 
2 The two ganglia of the Plerus splanchnicus 
or Sympathicus anterior, which is situated more 
or less in front of the inferior portion of the cesoph- 
ageal ring, have, together with their correspond- 
ing nervous filaments, already been regarded 
by Cuvier as a sympathetic system, with several 
G poda ; see his Mém. sur le Genre Aply- 
off eight pairs of nerves; Part V. Pl. II. fig. 13 
(Doris), cerebral ganglia, five pairs, and a single 
ganglion, —the pairs are symmetrically placed 
with regard to the median line and give off fifteen 
pairs of nerves; the single or visceral ganglion 
gives off four nerves which are distributed to the 
organs of reprod , to the st sh, to the two 
heurts. and to the branchiae, and can be traced 
into ganglia of the sympathetic system belonging to 
these several organs; Part V. Pl. XLIII. fig. 10 
{Antiopa), cerebral ganglia, six, and give off ten 
or eleven pairs of nerves. 
With all these genera, the cesophageal ring is 
formed by lateral commissures which unite with the 
sub-cesophageal ganglia which are sometimes two 
(Dendronotus, Doto, E is), ti four 
(Eolis, Doris, Antiopa).— Ep, 
*([§ 208, note 11.] The nervous system of the 
terrestrial Gasteropoda has been most carefully 
described and beautifully figured by Leidy (loc. 
cit.). The details are so full that I can only indi- 
cate the work. — Ep. 
