168 THE UNIVERSITY SCIENCE BULLETIN. 



ECHINOSTOME CERCARIiE. 



Of one hundred specimens of Physa gyrina collected at Law- 

 rence, Kan., August 19, one was infected with Cercaria fusiformis. 

 This species is characterized by a symmetrical spindle-shaped 

 body with a long digestive tract extending from the oral sucker to 

 near the caudal end of the body. While this species had all of the 

 characteristics of the echinostome cercariae, no spines are present 

 anywhere. The region of the oral sucker presents a collared ap- 

 pearance. The total length of this cercaria is .77 mm. and the 

 width is .07 mm. The oral sucker has an external diameter of 

 .028 mm. and an internal diameter of one-fourth that size. The 

 ventral sucker is about the same size and is capable of being greatly 

 extended or projected. This form used the ventral sucker exten- 

 sively in holding fast to the substratum. 



The digestive diverticula do not inclose the ventral sucker as 

 one would infer from the dorsal aspect, but are dorsal to it in lat- 

 eral view. The digestive tract consists of a very narrow esoph- 

 agus leading from the mouth to the pharynx. Just back of the 

 pharynx is a median intestine extending as far as the anterior end 

 of the ventral sucker, where it branches into two diverticula that 

 extend back to the posterior end of the body. The esophagus 

 measures .003 mm. wide and .03 mm. long. The width of the 

 pharynx is .018 mm. and that of the intestine .012 mm. 



The excretory tract consists of narrow paired tubes extending 

 from the region of the pharynx to the posterior end of the body. 

 The excretory bladder and the excretory duct, in the anterior part 

 of the tail, could not be traced definitely, but appeared as more 

 transparent areas in the toto mount. 



The anlage of the reproductive organs is a dense mass of cells 

 near the posterior end of the body. 



The posterior sucker is very muscular. The figures accom- 

 panying the plate show this sucker open, closed, and extended. 



The redise are large and contain from six to eight mature cer- 

 carise, together with a few large germ balls. They are distended 

 in places by the cercarias contained within. The average measure- 

 ments of the redise are, length 1.91 mm. and width .13 mm. to 

 .33 mm. 



GYMNOCEPHALOUS CERCARIA. 



Of fifty specimens of Physa integra collected at Chanute, Kan., 

 October 17, two were infected with Cercaria gracilis. I propose 

 this name because of the ability of the species to draw itself out 



