480 PROCEEDINGS OF THE ACADEMY OF [Sept., 



Of the more peripheral portions of the nervous system the buccal 

 ganglia are situated in the head region slightly attached to the 

 dorsal face of the radular musculature. From the commissure 

 uniting them two delicate nerves are given off, which course ven- 

 trally but rapidly become lost to view among the surrounding muscle 

 bundles. The connectives to the cerebral ganglia arise from the 

 forward borders of each buccal ganglion, extend laterally and ante- 

 riorly over the buccal musculature for a short distance, whereupon 

 they pass between some of the bundles of radular muscles to the 

 ventral side of the head. In this position, at each side of the under 

 surface of the radula, they pursue a course posteriorly to the cerebral 

 ganglia. Immediately after reaching the ventral surface of the 

 head they are united by a delicate commissure. 



Each cerebral ganglion gives rise anteriorly to one or two nerves, 

 in addition to the buccal connective, which innervate the head. 

 Where one nerve appears it soon divides into an outer and inner 

 branch destined to supply the tentacle and lips, respectively. The 

 relatively strong tentacle nerve gives off a short, stout nerve to the 

 eye and, after dividing, extends far towards the tip of the tentacle. 

 The inner, or lip nerve, passes by a fairly direct path to the dorsal 

 side of the head, and ultimately breaks up in the tissue about the 

 mouth. 



The pedal ganglia usually develop four pairs of nerves. The 

 most anterior, springing from the forward border of the ganglion, 

 extends through the pedal musculature to the forward section of the 

 foot, where each branches repeatedly and becomes lost among the 

 muscle fibres. Two other pairs extend ventrally and likewise soon 

 disappear in the compact pedal musculature. In addition to these 

 three pairs, each pedal ganglion gives off from its antero-dorsal 

 surface another nerve destined to supply the base of the neck. On 

 the left side of the body the bundle is comparatively slender and 

 soon becomes lost to view at the junction of the head and mantle. 

 On the right side the corresponding branch has the same size and 

 apparent distribution in lately hatched individuals, but at a later 

 period it becomes greatly enlarged and supplies the penis, which 

 arises relatively late in life. It may be added that the pedal 

 ganglia are united by two commissures, the usual heavy one and 

 another, much more delicate, posterior to it. 



The elements of the visceral loop comprise three clearly denned 

 ganglia, the sub-intestinal, the supra-intestinal and the visceral. 

 The first named is a globular body of approximately the same size 



