44 ILLINOIS BIOLOGICAL MONOGRAPHS [324 



single, and internally they unite with ducts from the longitudinal vitel- 

 line ducts to form the vitello-vaginal canals, as described for the 

 other species. They do not open separately into the ootype, but the 

 two vitello-vaginal canals open into a common reservoir from which a 

 duct passes dorsad and discharges into the ootype (Fig. 32). In a few 

 of the specimens the uterus is empty and in others it contains a single 

 large egg, the size of which varies within wide limits. The smallest 

 eggs are 0.11 by 0.25 mm. and the largest 0.18 by 0.34 mm. The pos- 

 terior edge of the uterus is at the level of the vaginae, and anteriorly 

 there is a small duct from the uterus to the ventral posterior part of 

 the genital atrium. The genital pore is in the median line, a short 

 distance posterior to the bifurcation of the alimentary tract. 



The excretory pores are slightly more posteriorly situated than in 

 the previous described species. Descending and ascending ducts occupy 

 the characteristic positions. 



POLYSTOMA OBLONGUM Wright 1879 



This species was described by "Wright (1879) from the urinary 

 bladder of Aromochelys odoratus. I have had no opportunity to work 

 on material of the species and the following discussion is based on the 

 description of Wright. According to that author P. oblongum measures 

 up to 2.5 mm. in length and 1.5 mm. in width. The body is oblong in 

 shape, tho capable of considerable variation. The caudal lamina is some- 

 what narrower than the greatest width of the body and is shorter than 

 broad. The arrangement of the suckers and hooks is similar to that in 

 P. integerrimum; the suckers are 0.2 mm. in diameter; the large hooks 

 are 0.15 mm. and the small hooks are 0.015 mm. in length. 



The mouth is on the ventral surface of the rounded anterior end. 

 The pharynx is bowl-shaped and the intestinal ceca are without anasto- 

 moses or branches. The description of the excretory system is very 

 meager; concerning it he says that only the convoluted lateral stems 

 were observed near the anterior end. 



The testis is situated in the posterior third of the body, the vas 

 deferens passing dorsad and anteriad to the genital pore, which lies im- 

 mediately behind the bifurcation of the intestine. The cirrus coronet is 

 described as consisting of sixteen alternately large and small hooks. The 

 free end of each is sharply curved, while the attached end is shaped like 

 a cross the transverse piece of which is longer on one side than the other. 

 The longer pieces measure 20/x and the shorter ones 15/*,. 



Doubt is expressed concerning the disposition and relations of the 

 female organs. The ovary is described as situated in front of the testis 

 on the right side of the body, but it seems probable that the organ figured 



