349] XORTH AMERICAN PARAMPHISTOMIDAE—STUXKARD 69 



orgaus, and the suckers are especially well supplied with l.ympli sinuses. 

 Excretory System. — The excretory pore is in the median line on tlu; 

 dorsal surface, near the posterior end of the body, and the median teriui- 

 ual vesicle extends interuallj- and anteriorly. It gives off a brancli to 

 either side and these branches of the collecting vesicle pass auteriad, 

 winding about the cecum of either side in many loops or coils. In sections 

 (Fig. 64) the tube may appear on either side, above, or below the cecum; 

 in a single section it may be cut in two or three places or a loop may piiss 

 half to two-thirds of the way around the cecum. No connections betw-.-en 

 the collecting ducts of the two sides could be seen, and they were traced 

 to the region of the oral sucker. 



ALASSOSTOMA PARVUM Stunkard 1916 



[Figures 66 to 71] 



Three individuals of this species were collected from the cloaca of 

 a single specimen of ChAydra serpentina from Urbana, Illinois. One 

 was retained as an alcoholic specimen, one was stained and mounted as 

 a toto preparation, and the third was cut into cross sections. 



The worms (Fig. 66) are thick with almost parallel sides, rounded at 

 the posterior end and tapering slightly anteriorly. Just in front of the 

 acetabulum the body narrows sliglitly and then widens posteriorly due 

 to the presence of two lateral prominences or evaginations, one on either 

 side at the level of the anterior part of the acetabulum. The worms are 

 2.8 to 3 mm. long and 0.78 to 0.08 mm. wide, the points of greatest width 

 are at the level of the testes and thru the posterior lateral prominences. 

 The sectioned worm is 0.8 mm. in width and 0.54 mm. in thickness. The 

 acetabulum is subterminal, oval, 0.8 mm. in length and 0.7 mm. in width 

 in the toto preparation. The inside measurements of the same sucker 

 are 0.56 mm. in length by 0.4 mm. in width and the opening is 0.45 mm. 

 in length and 0.21 mm. in greatest width. 



Alimentary Tract. — The oral sucker is terminal, ovoid, 0.46 ram. 

 long by 0.37 mm. wide, and in tlie sectioned worm 0.32 mm. in depth. 

 In the mounted specimen tlie sucker is widest posteriorly, and from the 

 posterior dorsal part on either side there is an oral evagination. These 

 arise separately and are 0.055 mm. long. Among the fibers of the oral 

 sucker there are many nuclei ; they are situated in the peripheral half 

 of the sucker and are confined to the central two-thirds of the external 

 half. There are also among the nuiscle fibers glandular cells with ducts 

 to the lumen of the sucker. The esophagus is somcMiiat coiled but ex- 

 tends thru 0.2 mm. and is surrounded by large deeply staining gland 

 cells. The posterior part is enlarged by the thickening of the annular 

 muscles of the wall which forms the esophageal bulb (Fig. 70). This 



