52 COMPARATIVE ANATOMY. 



From the cephalic ganglia nerves may be seen passing 

 anteriorly to supply the tentacles, 'Semper's organ,' and the 

 adjacent parts. From the upper or parieto - splanchnic seg- 

 ment of the sub-cesophageal mass nerves are given off to the 

 parietes and viscera. Of the visceral nerves, the peripheral 

 divisions have been removed, their origins alone remaining. 

 From the lower or pedal segment a leash of nerves passes 

 off to supply the muscular foot. A black bristle (the longest 

 of the two) has been inserted into the foramen which gave 

 passage to the anterior branch of the aorta. 



In the angle which the gullet makes with the buccal mass, 

 and situated on the latter, is the right stomato-gastric ganglion 

 of the sympathetic system. 



Of the generative organs, the hermaphrodite gland (situated 

 at the bottom of the right side of the tablet) is connected by 

 a single convoluted duct with the large, somewhat irregularly 

 shaped, and coarsely lobulated albuminiparous gland. 



The duct, on emerging from the gland, is of much larger 

 size and plicated. It has associated with it throughout 

 the greater portion of its length a ribbon-like granular pros- 

 tatic mass. Immediately above the pulmonary sac this sub- 

 divides into a long thread-like -duct, or 'vas deferens,' which 

 joins the root of the penis, and a short, thick oviduct which 

 opens outwards. 



In the re-entering angle between the penis and the oviduct, 

 and communicating with the latter, is the globular spermatheca. 

 The penis, pinned by its retractor muscle a little to the right 

 of the right superior tentacle, is seen to communicate by its 

 saccular portion with an aperture common to it and the oviduct. 

 The 'inultifid vesicles,' and 'dart sac,' so characteristic of the 

 majority of the European Helicidae, are absent. 



83. A Black Slug (Arion empiricorum), dissected to shew 

 its general anatomy. 



The structure of this species differs in no very important 

 respect from the last. The most noteworthy points of dis- 

 tinction are the following: the extremely lobulated and dif- 

 fuse character of the salivary glands and liver; the large 

 and compact hermaphrodite gland, and the smaller and more 

 finely lobulated albuminiparous gland. The spermatheca also 



