144 PROCEEDINGS OF THE ACADEMY OF [Mai'ch, 



Two pairs of nerves, in addition to the two commissures (Pc), 

 arise from the pedal ganglia. The first of these is — 



PI, a fairly heavy bundle springing from the side of the ganglion. 

 Coursing through the dense mat of muscle and connective tissue 

 composing the body wall, it extends posteriorly and ventrally, and 

 divides at the junction of the body and head (PI. XIII, fig. 11). The 

 anterior branch supplies the body wall adjacent to the head, and 

 sends a ventrally directed division to join the extensive plexus 

 located in the foot. The posterior branch is distributed over the 

 antero-lateral body wall, and in some instances also appears to be 

 connected with the pedal plexus, though this has not been established 

 with complete certainty. 



P2 is a nerve likewise originating from the lateral surface of the 

 pedal ganglion, but posterior to the foregoing nerve. Extending 

 laterally and posteriorly, it divides opposite to the stomach into an 

 anterior and posterior branch. The anterior division supplies the 

 body wall posterior to the area adjacent to the 'external reproductive 

 opening, and, extending to the foot, unites with the pedal plexus. 

 The posterior branch continues posteriorly to a point about opposite 

 to the level of the vas deferens, where it divides. The ventral 

 division pursues a fairly direct course to the foot, where it unites 

 with the pedal plexus. The dorsal branch continues its way along 

 the side of the body to the posterior end of the animal. Throughout 

 its course it develops at least four connectives which unite with the 

 pedal plexus. Approximately one-third of its length beyond the 

 point of origin, P2 gives rise to two dorsally directed branches. The 

 anterior one passes forward and appears to anastomose with nerves 

 from offshoots of x and y (fig. 12) arising from the pleural ganglion. 

 The posterior branch, a slender nerve, pursues a course posteriorly 

 and dorsally, and more or less parallel with P2 extends to the hinder 

 end of the body. Throughout its extent it develops four branches, 

 which pass into the dorsal lappets and about the anal opening, since 

 this normally replaces one of the lappets on the right side. 



The pedal ganglia are united by two commissures (Pc), the heavier 

 one being anterior. 



Four pairs of nerves usually pass out from the pleural ganglia. 

 In certain cases this may become obscured on one or both sides 

 through fusion or the presence of heavy connectives. In addition 

 to these paired nerves, a single one — 



G, appears on the right side (PI. XIII, figs. 11, 12), emerging at a 

 point close to the union of the pedal and pleural ganglia. Coursing 



