353] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD IZ 



.cephalic part extends anteriad about 0.46 mm. from the anterior margin 

 pf the opening of the sucker. The opening of the acetabulum is oval 

 approximately 1.1 mm. in length and 0.74 mm. in diameter. The sep- 

 tum or partition which divides the sucker extends almost to the opening 

 ^nd appears to separate an anterior circular part from the remaining 

 portion but there is a single oval opening of the acetabulum. 



The euticula is unarmed, slightly thicker on the dorsal surface. On 

 the ventral surface it is about 12/x in thickness and reaches 30/ti in thick- 

 ness on the dorsal surface. It is not homogeneous, but is traversed by 

 fine crinkled lines extending from internal to external surfaces, which 

 give it a reticulated appearance. The entire dorsal surface of the body 

 is underlaid with large gland cells filled with a substance staining deeply 

 with haematoxylin ; and their ducts lead to the dorsal surface. The con- 

 tents of the gland cells and their duets have the same appearance and 

 staining reaction as the euticula of the external surface. The dermo- 

 piuseular sac consists of the usual circular, longitudinal, and oblique 

 layers, the circular layer is next to the euticula. From the body wall 

 there are many large dorso-ventral muscle strands extending thru the 

 body. 



Alimentary Tract. — The oral sucker is subterminal, circular or 

 slightly oval in shape, 0.37 to 0.53 mm. in diameter. The oral evagina- 

 tions are 0.15 to 0.22 mm. in length and 0.07 to 0.1 mm. broad ; they 

 branch one on either side from a common sinus (Fig. 74) which opens 

 into the dorsal side of the posterior part of the oral sucker. The esoph- 

 agus leads from the oral sucker to the intestine ; it is 0.05 to 0.37 mm. 

 in length and is surrounded by a layer of deeply staining cells. Its 

 caudal portion is surrounded by an esophageal bulb. This structure is 

 oval, 0.2 to 0.45 mm. in length, 0.18 to 0.23 mm. in width, and 0.35 mm. 

 in thickness in the specimen cut in cross sections. It is situated obliquely 

 in the body, the anterior end is ventral and the posterior end more dorsal 

 in position. The muscles are not arranged in concentric lamellae as in 

 the previously described paramphistomes ; there is a capsule of external 

 longitudinal fibers and the body of the organ is composed of fibers ex- 

 tending on the sides from the central canal to the external capsule and 

 above and below the canal the fibers extend across from the lateral walls 

 of the bulb (Fig. 73). The alimentary tract is lined with euticula to 

 the bifurcation. The ceca are flattened laterally and the lateral walls 

 are sinuous giving them a very irregular appearance. They have a mus- 

 cular wall composed of outer circular and inner longitudinal fibers and 

 extend almost to the opening of the acetabulum, about 0.1 to 0.15 mm. 

 intervening. They terminate just caudad of the excretory pore. 



Male Reproductive Organs. — The testes lie one behind the other in 



