ELEMENTARY BIOLOGY. [CHAP. 



wards from the pedal ganglion of the same 

 side (b. ft). 



A long slender cord which passes directly 

 backwards from each beneath the organ of 

 Bojanus and joins the parieto-splanchnic gan- 

 glia of the same side (c). 



b. The pedal ganglia. 



u. Lay the animal on one side and proceed gently 

 to scrape away the tissues of the foot at about 

 the junction of its anterior with its middle 

 third, where the muscular and the visceral 

 portions of the foot join. The pedal ganglia 

 will thus be brought into view. They are a 

 pair of deep-orange-coloured oval bodies, each 

 rather larger than a big pin's head; they are 

 applied to one another in the middle line. 

 From each ganglion one commissural cord 

 (a. ft) passes forwards and upwards to the 

 cerebral ganglion of its side, and branches are 

 given off to the muscles of the foot and to the 

 auditory organ. 



The parieto-splanchnic ganglia. 



a. This pair are readily found by turning the 

 animal on its dorsal side, and dissecting away 

 the integument from the ventral surface of the 

 posterior adductor muscle. 



p. Trace forwards from each the cord (a. ft) 

 which runs to the cerebral ganglion of the 

 same side. It is easy to follow the commissure 

 so long as it lies in the region of the organ of 

 Bojanus difficult further on. 



