234 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



intestinal and visceral ganglia, and Guiart claims to have 

 found traces of this fusion in Aplysia. Both Guiart and 

 Mazzarelli deny that any nerves arise from the pleural ganglia 

 in Aplysia. Pelseneer, however, figures a p) euro-pedal plexus 

 in Aplysiella petalifera. 



C. Pedal Ganglia and Nerves. 



Each pedal ganglion (fed. g.) lies close to the pleural ganglion 

 of its side. A stout cerebro-pedal connective runs between 

 it and the cerebral ganglion, and a pleuro-pedal connective 

 between it and the pleural ganglion. From it arise the 

 numerous nerves supplying the foot and parapodia. The anterior 

 portion of the ganglion bears a hollow sac, the "otocyst" 

 (Fig. 23, ot.), which receives a slender nerve from the cerebral 

 ganglion (nerve A6). The pedal ganglia are united by two 

 commissures, known as the pedal and parapedal commissures 

 respectively. The former is a broad commissure which lies 

 ventral to the oesophagus and thus completes the cerebro-pedal 

 nerve ring. (Fig. 23, ped. comm.) The parapedal commissure 

 (para. ped. comm.) is long and slender, and is ventral not only 

 to the oesophagus but also to the aorta. : The aorta, therefore, 

 passes through the space between the two commissures. The 

 parapedal commissure gives off a small nerve on the left side 

 to the connective tissue in this region. 



The pedal nerves may vary in number and distribution 

 in different specimens. Those on the right side are always 

 larger and more numerous than those on the left, since they 

 are distributed to such asymmetrically placed structures as the 

 penis, genital groove, etc. 



1. Anterior pedal nerve. This large nerve arises from 

 the ventral side of the pedal ganglion and divides into four 

 branches, all of which supply the foot. The first or deep branch 

 is hidden by the second and third in dissection and runs forward 

 to the anterior portion of the foot. 



