36 Papers from the Marine Biological Laboratory at Tortugas. 



icle, its base overlapping the anterior edge of the ventral sucker. The 

 metraterm lies on the left side of the cirrus-pouch. Testes 2, oval, about 

 half-way between the ventral sucker and the posterior end, diagonally 

 placed and near together. Ovary about 4-lobed on right of median line 

 near right anterior border of anterior testis. Vitelline glands diffuse, 

 somewhat scattered, behind testes, and marginal to about the level of the 

 bifurcation of the intestines. Uterus between anterior testis and ven- 

 tral sucker; ova large. Excretory vessel a straight, median tube from 

 the posterior end to caudal edge of ovary where it divides, the 2 lateral 

 branches reaching the level of the pharynx. Numerous anastomosing 

 vessels surroimd the oral sucker (fig. 55 exv). 



Dimensions in balsam: Length 1.85; breadth 0.67; neck 0.71; oral 

 sucker 0.15; pharynx 0.08; ventral sucker 0.24; ova 0.078 by 0.044. 



Hamacreadium consuetum gen. et sp. nov. (Figs. 56-59.) 



Body ovate, flattened, oral sucker subterminal, pharynx adjacent to 

 oral sucker; esophagus usually as long as pharynx or longer; intestinal 

 rami extend to the posterior end of the body; ventral sucker 1.5 times 

 the diameter of the oral sucker, or more. Neck approximately one- 

 third the entire length. Reproductive aperture median, immediately 

 behind the bifurcation of the intestines. Cirrus-pouch overlaps anterior 

 edge of ventral sucker, or it may pass for a short distance to one side, 

 usually the right, but it was not seen to reach as far as the middle of the 

 ventral sucker. The seminal vesicle and prostate gland are both inclosed 

 in the cirrus-pouch. Testes 2, oval, one diagonally behind the other on 

 opposite sides of the median line, about midway between the ventral 

 sucker and the posterior end. Ovary lobed, somewhat variable, near 

 anterior border of posterior testis, with the oval seminal receptacle on its 

 dorsal surface, in some cases extending much beyond the anterior border 

 of the ovary. Vitelline glands diffuse, along margins as far forward as 

 the pharynx. Folds of the uterus between the testes and the ventral 

 sucker. The metraterm passes to the left of the cirrus-pouch to the 

 genital aperture; ova relatively large with a tubercle at one pole. 



The principal variations noted in the distomes referred to this 

 species were in the position of the cirrus-pouch and in the outlines of 

 the ovary. The cirrus-pouch in worms which were well extended lay 

 in front of the ventral sucker with the posterior end but slightly over- 

 lapping. In those which were more or less contracted the cirrus-pouch 

 lay at one side of the anterior border of the ventral sucker, but did not 

 extend as far as the middle of that organ. The ovary is sometimes dif- 

 ficult to make out on account of the dense masses of yolk-gland which 

 often overlie it. In some it appeared to be bilobed, but usually deeper 

 focussing or viewing from the opposite side brought another lobe into 

 view. In one specimen there were as many as 5 lobes visible. The 

 seminal receptacle is dorsal to the ovary, as shown in the figure, and 

 extends much in advance of the ovary. This was the case in the 5-lobed 

 ovary. 



Some are much more broadly ovate than the one shown in fig. 56. 

 This was particularly true in specimens from HcBtnulon sciurus. In these, 



