338 Olive B. Bavies : 



ganglia a number of nerves pass to the foot, and from the vis- 

 cero-pleural ganglia nerves pass to the body wall and to the 

 different viscera. The ganglia consist of nerve fibres in the 

 centre, and surrounding these the typical ganglionic cells, large 

 and granular, Avith branching processes and very distinct 

 nuclei, and smaller granular nucleated cells. The whole gan- 

 glion is bounded by an outer fibrous membrane. 



Sense Organs. 



These are the eyes, otocysts and sense papillae. 



The Eyes do not differ from those of other forms. 



The Otocysts (Figs. 8 and 16) are two semi-lunar sacs situ- 

 ated on the outer dorsal sides of the pedal ganglia. The walls 

 of these sacs appear to be formed by a thickening of the outer 

 membrane of the ganglia. In the walls are rounded granular 

 cells. The cavities contain minute particles, which I take to be 

 the calcareous otoliths, although I could not prove them to be 

 calcareous, probably owing to the acid I had used in staining 

 my specimens. In the inner corner of each otocyst is a minute 

 patch of cilia. The auditory nerves run down beside the pleural 

 ganglia to enter the posterior ends of the otocysts, having 

 their origin in the cerebral ganglia. 



Pedal Gland. 



Pedal gland (Figs. 5 to 12). This is a large gland extending 

 down almost the entire length of the foot, becoming larger at 

 its anterior and posterior ends, the median portion being com- 

 pressed by the visceral mass. It has a ciliated opening anteriorly 

 (Fig. 5) in the mid-line between the snout and anterior part 

 of the foot, and a posterior opening by the caudal mucous pore. 

 It consists of large, slightly granular gland-cells, with large 

 rounded granular nuclei and distinct nucleoli, connective 

 tissue and small granular cells. A great deal of mucus is pre- 

 sent, and takes the stain very readily. The median walls of 

 the gland surround a space which is ciliated, more particularly 

 the anterior portion. This acts as a duct for the gland. 

 Besides this large pedal gland the whole surface of the animal 



