242 INTRODUCTION. 



brandies to the muscular peritoneum ; 7th, branches to 

 the origin of the tentacular retractors ; 8th, branches 

 to the oviduct, ovarj, testicle, stomach, intestine, and 

 liver. 



From the stomato-gastric ganglia pass off on each 

 side, — 1st, a nerve to the external muscular structure 

 of the buccal body ; 2d, two branches which penetrate 

 posteriorly into the buccal body ; 3d, a branch to the 

 sahvary duct and gland ; 4th, a branch to the oesophagus 

 and stomach ; 5th, branch to the interior of the buccal 

 body anteriorly. 



The above distribution of the nerves has been princi- 

 pally derived from dissections of Glandina and Helix 

 albolahris. In the former genus, upon what is the nerve 

 to the inferior tentacle in the other genera, there is 

 formed, near the base of the tentaculte, a ganglionary 

 enlargement, from which passes off the true, inferior 

 tentacular nerve of this animal, and two other large 

 branches to the third, or external tentacle. 



The nervous centres are composed of ganglion glo- 

 bules, varying very much in size ; some are very large, 

 others are not more than one-eighth the diameter of 

 the larger ones and nuclear bodies. The globules are 

 more or less polygonal, from mutual pressure, are dis- 

 tinctly granular, and contain a nucleus which is com- 

 paratively of enormous size. The latter usually fills 

 one-half or two-thirds of the cell or globule, is more 

 distinctly and darkly granular, and contains from one 

 to seven small, round, transparent nucleoli. The sepa- 



