GENUS OF PARASITIC GASTROPODS. lOI 



proboscis which is concealed from view by a fold (not shown in 

 figure) springing from its base. From the study of sections it is 

 evident that this fold is of greater length than the proboscis and 

 is not united along the median line posteriorly. Externally the 

 fold is covered by a cuticular layer which is continuous over the 

 proboscis and within the digestive tract itself as far as the radula. 

 This last named organ is in a very rudimentary condition since it 

 consists of but a single tooth (Fig. 5, PI. I.) composed of some 

 finely granular substance staining intensely in Delafield's hsema- 

 toxylin. On each side of it are the openings of the salivary 

 glands which are doubtless the homologue of the ventral pair in 

 other molluscs. 



The main portion of each salivary gland consists of a large sac 

 located at the sides of the body proper as shown in Fig. i, PI. I. 

 The component cells are highly vacuolated structures containing 

 a faintly staining, granular secretion that is present also in the 

 adjoining cavity. Ventrally, in close proximity to the outlet of 

 this portion of the organ, the walls of the sac change abruptly in 

 character and consist of more slender non-staining elements 

 developed into low folds. Surrounding these cells are others of 

 considerably greater height that form a papilla projecting into 

 the cavity of the next division of the organ (Fig. 4, PI. I.). This 

 last named section is plain-walled and is composed of low 

 columnar cells containing small quantities of a finely granular 

 material, possibly a glandular substance differing from that of the 

 larger sac. At the base of the proboscis the walls become pro- 

 duced into several small folds before entering the slender canal 

 passing onward to its outlet at the side of the radula. Beyond 

 the radula the pharyngeal or oesophageal epithelium becomes 

 thicker and is attached to several muscle fibers acting as dilators 

 and constrictors. The opening into the stomach is on the 

 summit of a papilla whose general features are represented in 

 text fig. A. 



Opening into the oesophagus in close proximity to the stomach 

 are two sets of glands, that may correspond to the dorsal salivary 

 glands of other molluscs, whose position has shifted, though 

 there is a possibility that they are strictly oesophageal products. 

 Each group extends from the neighborhood of their outlet far 



