GASTROPODA, 



363 



innervates the vascular, excretory, and reproductive organs, and 

 also gives off from the supra- and sub-intestinal ganglia nerves to 

 the mantle, gills and osphradium. In all Gastropoda except the 



Ag 



FIG. 282. Nervous system of Paludina (after 

 v. Jhering). Cg cerebral, Pig pleural, Pg 

 pedal, Sp supra-intestinal, Sb sub-intestinal, 

 Ag abdominal ganglion ; o otocyst ; Eg sto- 

 matogastric (buccal) ganglion. 



CMtonidae the visceral com- 

 missure is asymmetrical, in 

 connection with the asymmetry 

 of the organs which it supplies. 

 In the arrangement which is 

 usually described as primitive 

 the cerebral ganglia are placed 

 at the sides of the oesophagus, 

 and are connected by a long 

 commissure ; the pedal ganglia 

 are drawn out into long gan- 

 glionic cords (Fig. 283, 15, Fig. 

 284, pe) extending along the 

 ventral surface (Aspidobranchs, 

 Paludina, Cydophorus, Cypraea), 

 and connected in a ladder-like 



manner by numerous commissures; the pleural ganglia are approxi- 

 mated to the pedal; and the visceral commissure is of considerable 



FIG. 283. Nervous system of Patella (from 

 Lang, combined after Pelseneer and Bou- 

 vier). 1 cerebral ganglion ; # cerebral 

 commissure ; 3 labial ganglion ; k buccal 

 ganglion ; 5 cerebro-pleural commissure ; 

 6 cerebro-pedal commissure ; 7 nerve to 

 otocyst 8; 9 pleural ganglion; 10 pedal 

 commissure ; 11 right, 12 left osphradium : 

 13 visceral ganglion ; lit supra-intestinal 

 ganglion ; 15 pedal cord ; 16 indication 

 of a sub-intestinal ganglion. 



