MOLLUSCAN GENUS COCHLITOMA. 



255 



protection for the brain and support for muscles, but they must 

 be deferred to a later date. 



The cerebral ganglia are joined by a stout commissure. The 

 several elements of the visceral commissure are very closely 

 united, and on the right side no distinction between abdominal 

 and visceral ganglia could be made out. On the left, the line of 

 demarcation between the visceral and pallial ganglia was fairly 

 plain, that between the visceral and abdominal less plain. There 

 are no pallio-pedal connectives, the centres being closely approxi- 

 mated. The pedal centres are likewise intimately fused to form 



Text-fiffure 4. 



Coclilitoma zebra var. obesa. 



Central nervous system (left moiety). 



cpdc. = ccrebro-pedal connective, epic. = cerebro-pleural connective, eg. = cerebral 

 ganglion, pg- = pedal ganglion, pig. = pleural ganglion, vag. — viscero- 

 abdominal ganglion. u».=visceral nerves. pZrt.=pallial nerves. pdn.=pedt\\ 

 nerves. 



a single mass, all that indicates an originally separate condition 

 being a faint median ventral furrow. The right side of this 

 complex is larger than the left. 



Pedal Nerves. — In counting the number of nerve-roots arising 

 from all ganglia, allowance has to be made for a certain amount 

 of error due to' the density of the sheath and the consequent 

 impossibility of being certain that adjacent roots are separate. 

 In z there are eighteen pedal roots on the left and sixteen (three 



