14 THE CHICAGO ACADEMY OF SCIENCES. 
minor nerve centers such as the BUCCAL GANGLIA, OSPHRADIUM, etc. All 
but the abdominal ganglion are paired. ‘these ganglia, with their 
nerves and commissures, may be briefly described as follows: 
The CEREBRAL GANGLIA (1) are situated above or a little to the 
side of the cesophagus and are joined to each other, to the pedal gan- 
glia and to the pleural ganglla by short, thick commissures. ‘These 
ganglia are made up of a number of small lobes, each ot which is 
probably the center for some particular nervous direction, The right 
cerebral ganglion sends a nerve to the male generative organ which 
divides betore reaching that organ, one branch going to the penis (15) 
and the other, which again subdivides, innervating the penis-sac (14). 
The cerebral ganglia also send nerves to the tentacles (12), optic 
nerves to eyes (10, 11), nerves to the front of the head (9), labial 
nerves to the region of the mouth (17) and a pair of nerves to the 
buccal sac. These latter or cerebral commissures enlarge on the buccal 
sac to form the buccal or stomato-gastric ganglia. A small nerve (13) 
arises from the posterior lobe of the right cerebral ganglion and 1n- 
nervates the region of the neck. Two nerves (32) supply the labial 
arteries. These ganglia also send out a number of small nerves which 
innervate the buccal sac and the manducatory organs. Branches are 
also sent to the salivary glands. 
The PEDAL GANGLIA (7) are very large, lie directly beneath the 
cesophagus, and are connected with the cerebral and pleural ganglia 
by short, thick commissures. These ganglia send off two sets of 
nerves of three each, the first, inferior and superior cervical and colu- 
mellar nerves (16, 18, 19, 26, 27) to the posterior part, and the second, 
superior, inferior and central pedal nerves (28, 29, 30) to the anterior 
part of the foot. There are several other short, minute nerves in- 
nervating the fore part of the body. The otocysts (31) are placed in 
the posterior part of the pedal ganglia, and are connected with some 
of the other ganglia by fine nerves. 
The PLEURAL GANGLIA (2, 6) lie below the cesophagus, and are 
connected by short, thick commissures with the pedal, cerebral and 
visceral ganglia. They apparently send off no nerve cords. 
The VISCERAL GANGLIA (3, 5) lie behind, and a little above the pleu- 
ral ganglia, and are connected with the latter and the abdominal ganglia 
by short commissures. The right ganglion sends off a long nerve (24, 
right pallial nerve) which innervates the female genital orifice, a por- 
tion of the respiratory cavity and the right posterior part of the 
mouth. Near the end of this nerve an enlargement forms the olfac- 
tory organ or osphradium (25). A shorter nerve (33, anterior pallial), 
