bloomer: on the British species of the genus solen. 19 



viscero-parietal ganglion. The direction of the connective after 

 leaving the ganglion is, for a short distance, between the retractor pedis 

 anterior muscle, and the ventral integument, then close to the side of 

 the muscle, and crossing over it continues along the side of the viscera, 

 afterwards passing through the wall of the retractor pedis posterior 

 muscle, and finally under the bifurcated portion of the muscle, to the 

 viscero-parietal ganglion (Figs. 18 and 20, V.P.G.). 



On the inner side of each cerebro-visceral connective runs a 

 cerebro-pedal connective (Figs. 18 and 19, Ce. P.). On leaving the 

 cerebro-pleural ganglion, the cerebro-pedal connective traverses a short 

 distance under and then on the inner side of the retractor pedis 

 anterior muscle, it then buries itself in the tissues of the foot, and 

 emerging into the pedal sinus, passes close to the longitudinal muscle 

 to the pedal ganglion. From this connective a nerve arises which 

 passes to the viscera. 



The pedal ganglia (Fig. 18, P.G.) are situated in the proximal part 

 of the foot, near its dorsal surface, and close to the most ventral fold 

 of the intestine. From them a number of nerves radiate which 

 innervate the viscera and the muscles of the foot. Passing along the 

 latter are four pairs of nerves, four nerves traversing each side, between 

 the longitudinal and transverse muscles, to the distal end. From these 

 a number of small branches arise. 



The viscero-parietal ganglia (Fig. 18 and 20, V.P.G.) are situated 

 between the bifurcated portions of the posterior retractor pedis muscle, 

 and anterior to the posterior adductor muscle ; like the cerebro-pleural 

 ganglia they can be seen through the transparent ventral integument. 

 Anteriorly they give rise to two branchial nerves (Figs. 18 and 20, 

 B.X.), one curving to the right and the other to the left, passing to the 

 base of the inner gills. They run immediately beneath the afferent 

 branchial vessels. 



From the posterior part of the ganglia the two posterior pallial 

 nerves arise (Figs. 18 and 20, P.P.N.). Each nerve passes under- 

 neath the posterior adductor muscle, and along the inner surface of the 

 dorsal' portion of the muscular part of the mantle lobes, formed by 

 their concrescence. On their way each gives off a large inner nerve, and 

 from both a series of smaller branches pass to the surrounding tissue. 



Near the muscular fringe of the posterior pallial band the posterior 

 pallial nerve divides, the outer branch crossing the mantle lobe 

 ventrally and first joining the inner circumpallial nerve, and afterwards 

 the outer circumpallial nerve. The other branch, in all probability, 

 passes around the base of the siphon, sending out branches to 

 it and the muscles of the mantle, and then joins the outer circum- 



