ANATOMY AND PHYSIOLOGY. 
Moll. 35 
in the substance to which the foot is applied or in the surrounding 
water. 
The nervous system of Ancylus fluviatilis differs from that of Gadinia , 
inasmuch as the oesophageal collar is very small and the buccal mass does 
not pass through it. The cerebral ganglia are pear-shaped, bifurcated 
above, the outer prominence giving rise to the ocular, tentacular, and 
lateral cephalic nerves; the inner dividing into branches for the lips, skin 
of the head, and the penis. The “ asymmetric centre ” consists of four 
ganglia, three ’of which belong to one side, one to the other ; it inner¬ 
vates the mantle, reproductive organs, branchial lamella, and heart. The 
otocysts are easily found on the dorsal aspect of the pedal ganglia. 
Lacaze-Duthiers (224). 
The nervous system of Gadinia garnotii consists of six ganglia, which 
are united to form two oesophageal collars, in addition to which there is 
a third, composed of an uneven number of ganglia, correlated with the 
asymmetry of the animal. The otocysts are seen by removing the pedal 
ganglia, and placing them under the microscope ; the auditory nerve fol¬ 
lows the usual rule of arising from the cerebral ganglia. The repro¬ 
ductive system is hermaphrodite ; the apertures are separated by the 
right eye, but are very small; Lacaze-Duthiers (222a). 
Bouvier (48) has examined the nervous system of Buccinum undatum, 
and finds two groups of ganglia united by a long visceral commissure. 
The anterior group is almost hidden in the salivary glands, and consists 
of 2 cerebral, 2 pedal, 2 commissural, 1 subintestinal, 2 sympathetic 
ganglia. The posterior contains only two ganglia on the visceral com¬ 
missure. Each cerebral ganglion has three sensory nerves—tentacular, 
optic, and auditory, and also a nuchal arising from the cerebro-pedal con¬ 
nective ; there are four nerves to the sheath of the siphon, and three, 
large and long, to the siphon itself. The pedal ganglion in the female 
is symmetrical, and gives off twenty-seven nerves, in addition to two from 
the upper surface, one of which goes below the mouth. In the male the 
ganglion is asymmetrical, owing to the presence of the penial nerve. 
The Pur pur idee, and the Buccinidce belong to the Chiastoneura of von 
Jhering ; the sub-intestinal ganglion, is, however, attached to the right 
commissural ganglion by an accessory connective, short in Purpura , and 
shorter in Buccinum ; in Coneholepas an intimate union takes place. The 
relations with the vascular system are very constant ; the anterior aorta 
passes below the visceral ganglia, and penetrates into the posterior and 
middle commissures, but below the anterior. The auditory nerve is con¬ 
nected with the cerebral ganglion ; the pedal ganglion gives off nerves to 
the penis as well as to the foot ; the right commissural ganglion gives off a 
single nerve to the walls of the body ; the left, in addition, several 
parietal nerves, the columellar nerves, and two constant branches, one 
siphonal, one to the pad situated between the foot and the columellar 
muscle ; the branchio-siphonal nerve gives off a branch to the olfactory 
organ of Spengel. In addition to characters drawn from the nervous 
system, may be mentioned the presence of a crop below the commissure, 
of a special oesophageal gland, and the absence of an efferent canal from 
the organ of Bojanus, which opens into the pallial cavity. Between 
