164 PROCEEDINGS OF THE NATIONAL MUSEUM vol.88 



either long or short oval-elliptical, or fusiform; neck very variable, 

 usually strongly contracted in preserved specimens. Oral sucker 

 subterminal, usually broader than long; prepharynx short; pharynx 

 of good size, usually longer than broad, approximately as long as the 

 oral sucker and about half as broad ; esophagus as long as or longer 

 than the pharynx, but often appearing shorter on account of the con- 

 tracted condition of the neck; intestinal rami with thick walls and 

 extending to the posterior end. The ventral sucker is much larger 

 than the oral, its opening transverse. The genital pore is in front 

 of the ventral sucker to the left of the median line, and about on a 

 level with the posterior end of the pharynx. The cirrus is smooth, 

 the cirrus-pouch long-pyriform, muscular, extending back of the 

 ventral sucker on the left side and enclosing a seminal vesicle at its 

 posterior end. A second seminal vesicle lies behind and beside the 

 posterior end of the cirrus-pouch. The second seminal vesicle and 

 the base of the cirrus-pouch are surrounded by cells of the prostate 

 gland. Testes, eleven in number so far as observed, roundish or sub- 

 triangular in outline, median, in two more or less irregular longi- 

 tudinal rows, in the posterior half of the postacetabular region. 

 Ovary small, about 3-lobed, in front of testes, and usually a little to 

 the right of the midventral line; in most cases behind the level of 

 the seminal vesicles, but in some cases on a level with the base of 

 the cirrus pouch, and near the ventral sucker. The shell gland and 

 yolk reservoir are at the posterior border of the ovary. There is a 

 seminal receptacle behind the ovary. It is dorsally placed with 

 respect to the ovary, and in compressed specimens may appear to be 

 to the right of the median line in some cases, to tlie left in others; 

 often it appears to be to the right of the median line and on a level 

 with the anterior testes. Laurer's canal was seen in a series of cross 

 sections (fig. 339). The diffuse vitellaria fill the greater part of the 

 space back of the testes and extend forward nearly or quite to the 

 ventral sucker. The uterus lies between the testes and ventral 

 sucker ; the metraterm lying beside the cirrus pouch and lateral to it, 

 joining the cirrus pouch very near the genital pore. The ova are 

 thin-shelled ; maximum in balsam about 0.060 by 0.036 mm. 



The relative positions of ovary, seminal vesicles, seminal recepta- 

 cle and first testes are subject to some variation with different degrees 

 of contraction, and with varying amounts of sperm in the vesicles. 



The main excretory vessel is conspicuous in living specimens, and 

 was traced from the terminal excretory pore to a point dorsal to the 

 ventral sucker. In series of cross sections the excretory vessel was 

 traced to the level of the ventral sucker, but the arrangement of the 

 excretory vessels in the neck was not satisfactorily shown. 



