720 Harozp HEATH, 
the inner face of the outher limb of the kidney and unites with the 
superior posterior ganglion, a relatively large nerve mass closely 
applied to the posterior cloacal wall which it equals in breadth. 
From this ganglion apparently all the nerves that innervate the 
various organs of the hind end of the body have their origin. A 
number of small fibres arise from it at the junction with the 
commissure from the pedal and pallial cords. Some of their branches 
may be followed for considerable distances over the cloacal wall, in 
some cases almost to its outer opening, while one small branch is 
distributed to the cells that guard the external renal opening. Three 
or four other divisions, more dorsal in position, pass backward and 
finally become lost among the somatic muscles. 
On either side of the mid line two strong nerves arise from the 
dorsal side of the superior ganglion. Each soon divides and of the 
two resulting branches the ventral one enters the base of the gill 
and, in close proximity to the efferent branchial sinus, passes along 
the upper surface of the dorsal gill retractor. In this position it 
may be followed to a point close to the apex. The dorsal branch 
soon takes a position between the pericardial and cloacal walls and 
dividing once or twice passes backward and finally penetrates the 
muscles at the extreme hinder end of the body. Two small twigs 
on each side of the mid line may be followed to the base of the 
dorsal sense organ. 
The two ventral branches from the superior ganglion arise from 
the under side immediately opposite the dorsal nerves. They rapidly 
penetrate the ventral gill retractors and are consequently somewhat 
difficult to follow but material killed in Vom Rarn’s fluid and 
examined with an oil immersion lens shows that throughout the first 
part of their course they pass down the dorsal wall of the rectum 
until they reach the junction of the ventral gill wall with the cloacal 
wall. Here each divides, one portion continuing its course along 
the rectum to the anal opening while the other bends abruptly out- 
ward and enters the gill. Almost at once it enters the blood sinus 
(afferent branchial vessel) and adjacent to the fibres of the ventral 
gill retractor makes its way to the tip. 
The paired gonad extends from the posterior end of the stomach 
to the pericardial cavity with which it is in communication by two 
relatively long and slender ducts (Figs. 6, 8). The sexes are separate 
and in several cases the germ cells had made their escape into the 
pericardial cavity. 
