90 



then cut through in the middle hne, and the two sides 

 reflected outwards from below upwards, the attachments 

 of the transverse muscle bundles being cut through as close 

 to the body- wall as possible. The whole course of each 

 cerebro-pedal connective is then exposed from the point 

 v/here it perforates the muscular body-wall to its ending 

 in the ganglion. The latter, with its nerves, is further 

 exposed by picking away the transverse muscle fibres and 

 the tubules of the gonad. 



The ganglion (Ga.p.) is elongated in a transverse direc- 

 tion, and is rather oblong in shape. The cerebro-pedal 

 connectives {Con. cp.) leave its upper and external borders. 

 Half-way between the pedal and cerebral ganglia each 

 connective gives off a small branch from its internal 

 surface, which enters into the viscero-pedal mass. 



Exclusive of the connectives four pairs of nerves radiate 

 out from the ganglion. These enter into the surrounding 

 tissue. One nerve, however, which is very thick, and 

 which leaves the lower border of the ganglion, can be 

 traced as far as the tip of the foot. 



The pallial plexus is formed by the three pallial nerves 

 described above. The anterior common pallial nerve, it 

 has been stated, bifurcates on leaving the anterior adduc- 

 tor muscle ; the inner of the two branches so formed gives 

 off a very fine nerve on its internal side, and thus three 

 pallial nerves, as in the case of the posterior common 

 pallial trunk, are formed. These three nerves are, of 

 course, identical with the three formed from the posterior 

 trunk, and so each pallial nerve has a double origin, one 

 extremity proceeding from the cerebral ganglion, the other 

 from the visceral. At about the centre of the mantle 

 margin, the middle and external nerves, which have 

 hitherto kept widely apart from each other, coixie together 

 and separate again, and at this point of contact a gangli- 



