88 



{b) Fruiii each pedal cord, tlie auteiior end of wliieli 

 may be called an ill-defiued pedal ganglion : — 



(1) From tlie anterior end, a nerve going forwards to 

 the foot and ventral body wall. 



(2) Xerves to the dorsal layers of the foot and to ihe 

 shell muscle. 



(0) Stout nerves to the ventral part (sole) of the foot. 

 (4) Fine nerves, those from one cord going towards 



those from the other. These nerves from the two cords 

 unite in two cases forming anastomoses, of which one 

 is close behind the pedal commissure, and the other 

 quite posterior. It is probable that these nerves and 

 anastomoses are vestiges of an ancestral ladder-like 

 condition of the pedal cords and their interconnections. 

 (c) From each pleural ganglion : — 



(1) Two small nerves (one more strictly from the 

 cerebro-pleural connective and one from the ganglion 

 itself) arising close together and supplying the dorsal 

 body wall. 



(2) A distinct nerve which seems to supply the anterior 

 end of the shell muscle. 



[IS) A small nerve arising near the lateral extremity of 

 the ganglion close to the origin of (4). 



(4j The great pallial nerve, which soon divides into 

 two : — (a) The anterior branch this again divides usually 

 into two; and (h) The stouter posterior branch— this 

 runs outwards with the anterior branch and then turns 

 backwards. At this point it may be seen just beneath 

 the tissue covering the foot when the visceral hump is 

 lifted oft'. This branch gives olf, from its outer side, 

 several nerves which run outwards to the mantle. Dr. 

 J. Travis Jenkins has shown by minute dissection that an 

 anastomosis does exist between the anterior and the 

 posterior branches of the pallial nerve (tig. 24j. It is. 



