No. 2.] NOTES ON DISTOMUM PATELLARE. 59 



an external limiting membrane into which muscle fibers are 

 inserted, and an internal non-cellular reticulum in which the 

 dermal muscles are embedded. A continuation of the subcu- 

 ticula sheaths the inner surfaces of the suckers. The dermal 

 musculature shows the usual arrangement, -- outer circular, 

 middle longitudinal, and inner diagonal fibers. The oral sucker 

 shows its adaptation to food-taking by the especial develop- 

 ment of sphincter fibers, while its extrinsic muscles are weak ; 

 the ventral sucker has few sphincters, but its base is fairly 

 sheathed in a powerful extrinsic musculature of protractors and 

 retractors, which pass in various directions from its sides to 

 the body wall, so that the sucker could readily be shifted in 

 position. The cellular structure of the parenchyma is distinct. 

 The peripheral or subcuticular cells are smaller and more 

 deeply staining than the rest, which look in comparison pale 

 and vacuolar. The subcuticular cells are most conspicuous in 

 the neck, but are coextensive with the cuticle. In the suckers 

 they are also scattered among the vacuolar parenchyma cells. 



D. patcllare resembles in internal anatomy (Fig. i) D. 

 folium, which is described by Looss J (a) as occurring in the 

 bladder of certain fishes. The digestive tract has no salivary 

 glands and no pharynx, although the thickened cuticle and 

 musculature of the oesophagus may present traces of a 

 pharynx. _ The intestinal epithelium has long abundant cilia. 

 Each cerebral ganglion gives rise to two anterior and two pos- 

 terior nerves, all of which give off branches which pass toward 

 the body wall. No commissures were seen between the main 

 trunks or their branches. The excretory system resembles 

 more closely than that of D. folium that of D. cygnoides which 

 occurs in the bladder of the frog and which Looss J (a) considers 

 closely related to D. folium. The excretory vesicle, which is 

 much elongated and has a slight fusiform expansion in front of 

 the excretory opening, has no epithelium, but the walls of the 

 excretory ducts from the point where they leave the vesicle 



1 Looss, A.: (a) Die Distomeii unserer Fische und Frcische, Bibliotheca Zoologica, 

 Leuckart u. Chun, 1894. 



(b) Zur Frage nach der Natur des Korperparenchyms bei den Trematoden, 

 Abhand. sacks. Gesell. d. Wiss., 1893. 



