626 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The buccal ganglia (Figure 9) are irregular in outline, each ganglion 

 consisting of two parts, the smaller of which lies on the lateral wall of 

 the buccal mass, while the larger is on its ventral surface. The buccal 

 commissure is short, lying on the ventral side of the buccal wall. 



Nerves. — In addition to the several commissures and connectives 

 already described, the ganglia have the following nerves. Each of the 

 cerebral ganglia gives off from its posterior surface a small, short nerve 

 which goes to the oviduct. From its dorsal posterior surface arises a 

 large nerve which bends ventrally, passing immediately back of the 

 optic ganglion. This nerve is enlarged on the right side of the body 

 by ganglionic cells. From this ganglionic enlargement some branches 

 pass to the distal portion of the oviduct and penis, others to the lateral 

 body wall and mantle edge. On the left side no corresponding gan- 

 glion was detected, the nerve simply giving off many branches to the 

 lateral and posterior body wall. The olfactory portion of the cerebral 

 ganglion is the source of the largest nerve in the body. This nerve 

 extends along the side of the pharynx, sending off to the rhinophore a 

 branch, which spreads out into a wide, much-flattened nerve that is 

 distributed to the integument of the rhinophore. The nerve continues 

 anteriorly beyond the base of the rhinophore giving off several branches 

 to the region around the mouth, while one branch enters the base of 

 the tentacle. Just dorsal and anterior to the olfactory lobe a small 

 nerve (Figure 9, n.) arises which goes directly to the integument dorsal 

 to the mouth. 



Each pedal ganglion sends to the foot two large nerves, the anterior 

 and posterior pedal nerves. On the right side a third nerve arises 

 from the posterior surface of the right pedal ganglion and goes to the 

 base of the penis. 



Each of the visceral ganglia gives off a single nerve which is dis- 

 tributed to the lateral and posterior wall of the pharynx and a small 

 nerve to the anterior genital mass. 



10. Histological Structure of the Pedal Ganglion. 



The several ganglia are essentially like one another histologically, 

 the conditions represented in the pedal ganglion being typical. Each 

 ganglion is closely invested in a connective-tissue capsule. Figure 1 1 

 is a longitudinal (parasagittal) section through the right pedal ganglion, 

 showing the cerebro-pedal connective on the left and the origin of the 

 anterior pedal nerve ventrally. There are a few large and many small 

 nerve cells having the base of the cell directed toward the connective- 

 tissue capsule. The number of nerve cells is much less in the ventral 



