34. 



Several branches are given to t'ne posterior extension of the 

 mantle. 



Each pedal ganglion gives rise to a nerve that runs 

 direct^ to the byssal gland, and to six or nore ner^.'^s that supply 

 the muscles of the foot. Frequently one neirre and sometimes sev- 

 eral ner^^es may run up the cerebro-pedal commissure for some dis- 

 tance before iss'aing to be distributed to the muscles of the foot. 



The nerve that supplies the otocyst issues from the 

 cerebro-pedal commissure but^ judging from the direction of the 

 fibres in the commissure, probably has its origin in the cerebral 

 ganglion. 



OTOCYSTS. 

 Figixres 4-., 21 and 22. 



The otocysts are rather large and, as Kellogg ' has 

 pointed out, each contains a single large otolith, whicia plainly 

 ■< shows concentric structure. The epithelial cells of the otocysts 

 carry rather long arid slender cilia. In adult- specimens there 

 IS a well defined canal connected with each otocyst. Pelseneer v"' J 

 describes this canal as opening at the surface of the foot and 

 gives a figure indicating the position of its opening. 



I have found that, by the careful dissection of speci- 

 mens preserved in formaline, the cerebro- pedal coirmissures, with 

 the otocysts, otocystic ner^res, and otocystic canals, all held 



