Helminth Fauna of the Dry Tortugas. 25 



to be found in the nature of the cirrus-pouch. In P. oval is it is relatively 

 short, reaching barely to the posterior edge of the acetabulum, while in 

 P. irroratus it extends far back of the acetabulum between the testes. 

 Body compressed, thickish when at rest; outline long-oval or ellipti- 

 cal, in some cases oblong with extremities bluntly rounded; living speci- 

 mens very active, the shape constantly changing; translucent with con- 

 spicuous excretory vessels. Oral and ventral sucker- about equal, the 

 latter about the middle of the body. Pharynx relatively large, longer 

 than broad, joined with oral sucker by a very short prepharynx; esoph- 

 agus very short, only discernible in sections. In transverse sections 

 the lumen of the pharynx, at its anterior end, is surrounded by 4 blunt, 

 tooth-like lobes (fig. 11). The rami of the intestines are capacious, 

 sacculate, with thick mucous membrane composed of large, granular 

 cells. In some preparations these cells have striated borders. The 

 intestines extend to the posterior end of the body. Each ramus sends 

 2 or 3 short diverticula? forward. The first diverticulum on each side 

 lies beside the pharynx and extends cephalad as far as the anterior end 

 of the pharynx. The genital aperture is immediately in front of the 

 ventral sucker, close to its anterior border, and a little to the left of the 

 median line. The cirrus-pouch, in most cases, lies along the anterior 

 border and right side of the ventral sucker; the anterior portion contains 

 the cirrus surrounded by prostate cells, the posterior portion contains 

 the convoluted seminal vesicle. There are some variations in the posi- 

 tion of the cirrus-pouch and of the genital aperture, as well as in the 

 proportions of the prostate and seminal vesicle. In the majority of 

 the cases examined the prostate occupied a little more than half the 

 length of the cirrus-pouch, and the genital aperture was very close to 

 the anterior border of the ventral sucker. Testes 2, opposite, lobed, 

 close behind the ventral sucker. The ovary is subglobular, subtriangular 

 to oval-elliptical in sections, and lies very close to the posterior border 

 of the ventral sucker, a little to the right of the median line, in front of 

 the right testis and close to its antero-median border. The shell-gland 

 with the seminal receptacle on its lateral border is dorsal to the ovarv. 

 Where best seen the seminal receptacle is globular and dorsal to the 

 posterior edge of the ovary. Laurer's canal opens dorsally opposite the 

 posterior border of the ventral sucker and near the median line. The 

 position of the vitellaria, as seen in the larger specimens in balsam, is 

 lateral and dorsal from a point on a level with the anterior edge of the 

 ventral sucker, then lateral only as far back as the posterior edge of the 

 testes. In other cases they extend from the anterior edge of the ventral 

 sucker or slightly in advance of that point to a point about midway 

 between the testes and the posterior end. In sections they were seen 

 to extend laterally nearly to the posterior end. They are diffuse and 

 somewhat dendritic. The voluminous folds of the uterus fill the body 

 behind the testes extending forward between the testes and dorsal to 

 them to pass to the left of the cirrus-pouch, where, as the metraterm, 

 it lies parallel to the cirrus-pouch and opens along with the cirrus at the 

 genital pore. The excretory vessels, while presenting very many differ- 

 ences of detail, were in general as represented in the sketch (fig. 14). 



