APLYSIA. 235 



2. Small tegumentary nerve. 



3. Tegumentary nerve. This large nerve supplies the 

 retractor muscles of the head, the skin, and, on the right side, 

 the muscle strands attached to the penis. It anastomoses with 

 the posterior tentacular nerve (A3). 



An additional small tegumentary nerve, occurring on the 

 right side only, supplies the skin and penis. 



All the above nerves run forwards. The following run in 

 a posterior direction. 



4. Parapodial nerve (Fig. 16, para. n. 1.). This is a 

 large nerve which arises from the ventro-lateral side of the 

 pedal ganglion and passes straight backwards ventral to the 

 longitudinal muscle bands and somewhat obliquely to innervate 

 the parapodium. It branches on its outer side only. 



5. Small tegumentary (teg. n. 7). This nerve springs 

 from the inner dorsal side of the ganglion, crosses dorsal to 4, 

 and runs beside the crop. It has three branches, viz., to the 

 body wall anterior to the genital aperture, to the parapodium, 

 and to the sub-pallium. On the right side it has an anastomosis 

 with the vulvar nerve (Dl) from the parietal ganglion and also 

 with the nerve from the pleural ganglion (Bl). 



6. Small parapodial (para. n. 2). This goes straight to 

 its destination and does not branch until it reaches the muscles 

 of the parapodium. 



7. Middle pedal nerve (ped. n. 2). It passes straight 

 backwards, crosses ventral to 8, and plunges into the middle 

 portion of the pedal sole. 



8. Posterior pedal (ped. n. 3). This large nerve inner- 

 vates the posterior portion of the foot, branching on the 

 surface of the muscle bands. An additional nerve, distributed 

 to the foot, may be present on the left side. 



D. Parietal Ganglion (par. g.). 



The parietal ganglion (supra-intestinal) lies beside, but 

 slightly antero- dorsal to the visceral ganglion, at the level of 



