196 



BULLETIN OF THE 



the dorsal median face to the visceral ganglion (Figs. 103 a , 112, 113), 

 and the anterior face to the cerebral ganglia (Fig. 107). No nerves 

 arise from the pleural ganglia. 



The visceral ganglia (Plate VIII. Figs. 103% 110-113) have also 

 moved nearer to the median plane. The left ganglion is directly below 



Figure G. — Posterior face of a transverse section from an embryo of the seventeenth day. x 60. 



ab. Abdominal ganglion. n. pd. 



art. ce. Cephalic artery. nph. 



art. pd. Pedal artery. nph. dx 



dt. sx. pr. Primary sexual duct. o cy. 



gl. sal. Salivary gland. pd. s. 



ffl pd. Pedal gland. pi. cr. 



hp. Liver. ret. ta. 



mt. Mantle. ret. ta. s, 



n. Nerve. vsc. s. 



Pedal nerve. 



Nephridial organ. 



Right nephridial organ. 



Otocyst. 



Left pedal ganglion. 



Pericardium. 



Retractor muscle of right ocular tentacle. 



Retractor muscle of left ocular tentacle. 



Left visceral ganglion. 



the oesophagus (Fig. Ill and Figure G), since the latter occupies a posi- 

 tion more to the left side of the body than before. The right visceral 

 ganglion still remains larger, and extends farther dorsally than the 

 left (Figs. 103 a , 111, 112). It is nearer the median plane than in the 



