[duff] THE BEAVER FLUKE 89 



pharynx is without true diverticula but there are, at about the middle 

 of its extent, two lateral pouchings of the cavity into the muscular 

 wall. These are quite extensive, irregularly shaped sacs, completely 

 surrounded by the pharyngeal muscles, each communicating with the 

 gut by a short narrow canal (Figs 1 and 6). At its posterior end 

 the pharynx narrows down to a short oesophagus which bends dorsal- 

 wards and divides to form the two arms of the intestine. These are 

 simple and unbranched; they run the length of the body as parallel 

 straight tubes which end blindly behind the ventral sucker. The 

 digestive tubes are filled with a mass of food stuff in which bits of 

 wood fibre are to be seen, showing that the worm is at least partly 

 nourished by the food of the host. 



Reproductive System. 



(1) Male genital organs. The testes are two large much lobed 

 sacs, lying one in front of the other in the middle ventral region of 

 the body. The anterior testis belongs to the right side although it 

 extends across the middle line; the posterior one is that of the left 

 side. The posterior lobes of the anterior (right) testis overlap the an- 

 terior lobes of the other. A single vas deferens arises as a narrow tube 

 from one side of each testis, runs forward with gradually increasing 

 diameter, and unites with the other in an elongated sac, the vesicida 

 seminalis. After bending sharply back on itself this leads into the 

 ductus ejaculatorius, the terminal part of the sperm duct, which lies 

 coiled in a strongly developed muscular cirrus sac (Fig. 3). The 

 presence of the latter is exceptional in the genus Amphistomum (10). 

 Before leaving the cirrus sac to enter the common genital sinus lead- 

 ing to the genital pore the ductus ejaculatorius is surrounded by cells 

 of glandular nature, the so-called "Prostate glands." 



(2) Female genital organs (Fig. 1). The ovary or germarium 

 lies in the middle of the body, a little to the left side, just in front 

 of the posterior sucker. The ripe ova pass backwards by a short 

 narrow oviduct which arises from the posterior dorsal region of the 

 ovary. Near its origin the oviduct gives off a backwardly directed 

 branch longer than itself, known as Laurer's Canal. This is a slender 

 median tube opening to the exterior on the dorsal surface about • 75 

 mm. in front of the execretory pore. No receptaculum seminis is present. 

 There are two yolk glands, each composed of numerous follicles closely 

 packed together, which extend on either side from behind the sucker 

 forward about half the length of the body. The bulk of them is below 

 the intestinal arms and they spread out close to the lateral body walls. 

 The two vitelline ducts, a straight tube from each vitellarium, unite 



