33O ELEMENTARY BIOLOGY. [CHAP. 



c. Carefully snip away the membranous tissue at the 

 base of the labial palps ; there will thus be laid 

 bare the cerebral ganglia. 



Each is about the size of a pin's head, and 

 somewhat triangular in form; it lies immediately 

 in front of the protractor pedis tendon, and dis- 

 tributes fibres to the anterior adductor muscle, 

 labial-palps and pallial lobe. Examine, in connec- 

 tion with the one exposed 

 a. the inter-cerebral commissure. 



A short cord uniting the two cerebral ganglia 

 across the middle-line, above the gullet. 

 /?. The further course of the cerebro-splanchnic com- 

 missure. 



Dissect off the fibrous tissue between the 

 anterior retractor and protractor tendons, and 

 remove the body-wall, between these and the 

 anterior end of the pericardium. The commis- 

 sure will be exposed, on carefully picking away 

 the superficial portions of the digestive and 

 reproductive glands along the same line. 

 tL Remove a small portion of the body-wall along the 

 point of origin of the muscular foot, and pick away 

 the genital gland until the pedal ganglia are reached; 

 they are a pair of deep-orange-coloured oval 

 bodies, each rather larger than a big pin's head, 

 applied to one another in the middle line, near the 

 point of junction between the body and the mus- 

 cular foot. 



Branches are given off to the muscles of the 

 foot and to the auditory organ. See infra. 



e. The cerebro-pedal commissure ; a cord which runs 



