SPECIAL ANATOMY. 241 



■while in Vaginulus it is so short that the two sets of gan- 

 glia form a close ring around the anterior part of the 

 buccal body. 



The third set of ganglia are the stomato-gastric, con- 

 sisting of two minute, lateral masses, united by a short, 

 transverse commissure, and always placed upon the buc- 

 cal body immediately postero-laterally to the commence- 

 ment of the oesophagus. The stomato-gastric ganglia are 

 connected with the supra-oesophageal on each side, by 

 means of a long, delicate commissure, which is more or 

 less loose, and permits a free movement of the former 

 ganglia with the buccal body to which they are fixed. 



From the supra-oesophageal ganglia pass off on each 

 side, — 1st, a minute branch along the course of the 

 supra-sub-oesophageal commissure ; 2d, three or four small 

 branches to the retractor muscles of the tentaculte ; 3d, 

 a large branch, the superior tentacular nerve ; 4th, one 

 or two small branches to the base of the superior tenta- 

 cle, for its integument ; 5th, the inferior tentacular 

 nerve ; 6th, small branches to the integument of the 

 lips. 



From the sub-oesophageal ganglia pass off, — 1st, nume- 

 rous branches on each side, to the podal disk, and late- 

 rally to the integument ; 2d, a branch on the right side 

 to the penis ; 3d, a branch to the vas deferens and pros- 

 tate gland ; 4th, on each side a branch to the retractor 

 muscle of the buccal body ; 5th, a large one to each side 

 of the collar and pulmonary chamber ; 6th, a branch 



which follows the posterior aortic vessel, which gives off 

 VOL. I. 30 



