60 ILLINOIS BIOLOGICAL MONOGRAPHS [60 



anteriad into the uterus. This organ has an outlet just behind the median 

 eye. It ends in a poorly developed vagina. No Laurer's canal has been 

 definitely made out in the totos but there is evidence of such an organ in sec- 

 tions. From the sides and sUghtly caudad to the ovary the closely massed 

 testes open into filiform vasa efferentia which unite anterior to the ovary to form 

 the vas deferens. This canal is directed forward parallel to the uterus, ending in 

 a bulbous cirrus pouch just to the left of the vagina. The three paired outer 

 vitelline follicular masses and the five paired iimer masses occupy a dorsal 

 position. They are irregular in contour (Fig. 4), with aciculate margins, and 

 are finely granular with close massing of the granules. Inconspicuous com- 

 mon viteUine ducts connect the vitellaria with the ootype just dorsal to the 

 ovary. 



The excretory trunks are similar to those of the entire group of monostomes. 

 The bladder is quite small, 48/i in section, moderately muscular, superficially 

 triangular, with the excretory pore posterior. The excretory tube in the tail 

 is vesicular at the base and narrows down distad (Fig. 4). The tubes of the 

 tnmk are crowded with large excretory granules. 



The digestive system is t3T)ically triclad, with ceca extending to the sub- 

 distal extremity. They are filled with a jell, and are crowded with granules 

 imbedded in the jell. No pharynx has been observed. The oral sucker is 

 directed ventrad. It is small but powerful. 



The parenchyma is filled with cystogenous granules, included in one-celled 

 cystogenous glands, probably of mesodermal origin (Fig. 14). Between the 

 cystogenous cells are angular parenchyma cells, more commonly known as 

 vesicular cells (Blasenzellen), with processes extending to the integiunent and 

 possibly functioning in the capacity of secretory ducts for the basement mem- 

 brane. 



The locomotor organs at the posterior angles of the tnmk are neither spicu- 

 late nor spinose. They possess no cement glands. The tail has no central 

 pair of gland elements such as axe found in binoculate cercariae of the mono- 

 stome group. However, the ordinarj' parenchyma cells of the tail of C. pelltt- 

 cida are remarkably large and vesicular and suggest a glandular function 

 (Fig. 19.). 



Large, isolated bands of transverse muscle fibers are present thruout the 

 body just within the basement membrane. Longitudinal muscles are not so 

 large in the tnmk as are the transverse series, but constitute the important 

 muscle system of the tail. The transverse muscles of the tail frequently give a 

 moniliform appearance to that organ, such as is described by Leidy (1877) for 

 Glenocercaria Iticania. 



The nervous system of C. pellucida (Fig. 23) varies from the distome nervous 

 system only in its relation to pigmentation and the eye-spots. There are six 

 anterior tnmks and six posterior trunks arising from a paired brain center. 

 They constitute the dorsal, lateral and ventral nerve lines. These trunks are 

 carefully followed by the melanoidin pigment fraction. The eye-spots receive 



