318 



PKOCEEDINGS OF THE MALA.COLOGICAL SOCIETY. 



Ampullaria, sp., in this point seems to represent an interesting stage 

 in the anterior concentration of the pedal ganglia, in which, although 

 the outward form of the scalariform pedal ganglion cords is retained, 

 the ganglion cells are already concentrated towards the anterior end, 

 and form definite pedal ganglia. 



With regard to the pedal ganglia and their commissure Bouvier 

 says : — " The pedal ganglia are united by a fairly long and very stout 



sp.int.g 



The pleuropedal ganglia and surrounding nerves of Ampullaria, sp. (enlarged). 



p. com. I. pedal commissure I. p. com. II. pedal commissure II. p. g. pedal 

 ganglion, p. cd. pedal cords, pi. com. pleural commissure, pi. g. pleural 

 ganglion. sh. int. g, subiutestinal ganglion. sp. int. g. supra-intestinal 

 ganglion. 



commissure. They project somewhat in front, and are fused behind 

 with the pallial (pleural) ganglia." This description is applicable 

 enough, as far as it goes, to Ampullaria, sp. ; but the commissure that 

 unites the pleuropedal ganglion masses is not a simple stout band ; on 

 the contrary, it is distinctly separable into three : ( 1 ) a broad flat 



