THE CARNIVOROUS SLUGS OF SOUTH AFRICA. 149 



and are distributed to all parts of the foot. The most 

 posterior nerves, which arise from the extreme hind end of 

 the ganglia, are the largest, and run back for almost the 

 whole length of the animal, as will be seen from fig. 75. 

 This figure also shows that the other pairs of pedal nerves are 

 not arranged quite symmetrically. The pedal gland is inner- 

 vated by a pair of nerves which bi'anch from the inner sides 

 of the most anterior pair of pedal nerves. The size of 

 these nerves to the pedal gland is in direct proportion to 

 the size of the gland itself; thus in Apera dimidia, with its 

 highly developed pedal gland, the nerve is larger than in A. 

 sexangula, as will be seen by comparing figs. 73 and 74. 



From the sides of the ventral group of ganglia a large 

 number of nerves radiate to the skin on each side of the 

 body and head, passing below the tentacular retractors, but 

 above the vagina and the adjacent part of the vas deferens on 

 the right side (PI. XIII, fig. 57). These are the nerves that 

 de Lacaze-Duthiers termed the "nerves of the neck." The 

 most posterior of these nerves can be seen running back on 

 each side along the inner surface of the body-wall sometimes 

 nearly as far as the diaphragm, thus confirming the hypothesis 

 that all this region of the skin corresponds to that of the 

 neck of ordinai-y snails and slugs. The posterior ends of the 

 common retractors of the tentacles also receive nerves belong- 

 ing to this group. All these lateral nerves appear to arise 

 by i-epeated branching from three main roots on each side 

 of the ventral ganglia. The most anterior root springs from 

 the outer edge of the pedal ganglion a little behind the 

 cerebro-pedal connective. The second arises from the junc- 

 tion of tlie pedal and pleural ganglia — that is to say, from the 

 very short pleuro-pedal connective. The third and most 

 posterior root arises from the pleural ganglion itself. Fischer's 

 figures of the nervous system in Rhytida ina^qualis {Pfi'-) 

 and the Oleacinidie also show nerves arising from the 

 pleural ganglia, but according to de Lacaze-Duthiers, Plate, 

 Wiegmann, and Beutler, no nerves arise from the pleural 

 ganglia in Testacella, Daudebardia, Ennea (Eden tu- 



