Helminth Fauna of the Dry Tortugas. 67 



genital aperture median, in front of the ventral sucker; ova large. The 

 character which suggests the nanie of the genus is the presence of con- 

 spicuous glands in the neck, which are interpreted to be yolk-forming 

 cells. 



Deradena ovalis gen. et sp. nov. (Figs. 162-169.) 



The following description is based on whole mounts and sections of 

 specimens from Scarus ccsruleus: 



Body smooth, oval, thickish, pale red, suckers about equal, neck 

 about 0.25 of entire length; pharynx longer than wide; esophagus rela- 

 tively long; bifurcation of intestine not far from posterior edge of ventral 

 sucker, the rami extending to the posterior end. Genital aperture at 

 anterior border of ventral sucker; no penis; genital pouch containing the 

 comparativel}' straight and strong-walled metraterm, which, near the 

 outlet, receives a small tube from the seminal vesicle (fig. 164 z) and is 

 dorsal to the ventral sucker; prostatic cells accompany both metraterm 

 and seminal vesicle. There was considerable difference in details in the 

 two series of sections as shown in figs. 164 and 165. One testis, large, 

 near posterior end of body. Ovary in front of testis and near it, nearly 

 median, its vertical diameter greater than the lateral; shell-gland ventral 

 and median to the ovary, as seen in sections; in whole mounts it is on 

 the anterior and lateral border of the ovary. In one of the whole mounts 

 the shell-gland extends along the entire anterior border of the ovary and 

 about half-way back on each lateral border. In the other it is so much 

 obscured by the vitellaria that it is difficult to see it at all. The vas 

 deferens is voluminous and was traced in sections from the posterior 

 end of the cirrus-pouch to the shell-gland. There is a large seminal recep- 

 tacle which is situated for the most part ventral to the shell-gland. No 

 Laurer's canal was recognized in the sections. The vitellaria are very 

 abundant and are distributed peripherally throughout the body. Large 

 cells extend from the body-wall into the parenchyma (fig. 168 d). At 

 their inner ends they are yolk-bearing (fig. 169 d and d'). I interpret the 

 cell to which the index line d^ points as having undergone nuclear division, 

 and the inner nucleus with thr mass of yolk surrounding it as about to 

 separate. The masses of yolk (fig. 169 vg) forming a concentric layer 

 within the layer of yolk-forming cells can be seen to be made up of cells 

 which resemble the inner ends of such cells as d\ These yolk-cells tend 

 to fuse together, their nuclei disappear, and the yolk is at first reduced 

 to a granular condition, as in the duct yd seen in longitudinal section in 

 fig. 169. Next it collects into coarse granular masses, as in the duct yd, 

 shown in cross-section in fig. 169. The folds of the uterus lie between 

 the ovary and the ventral sucker. There is a distinct excretory pore at 

 the posterior end of the body, and a straight excretory vessel appears 

 in the series of sections on the dorsal side as far forward as the anterior 

 border of the testis. My notes, made at the time of collecting, mention 

 in one of the specimens the occurrence of dark, lateral lines meeting be- 

 hind the ventral sucker whence the single tube extends to the posterior 

 end. Some very small vessels, which appear in the transverse sections 

 but which I have been unable to trace to the po-sterior single vessel, may 



