HYMEXOLEPIS NITIDA, KRABBE, AND E. NITIDULANS, KRABBE. 39 



taculum seminis. In this species, H. nitidulans, this " staerkt 

 lysbrydende oval-cirrusblaeren" of Krabbe is a muscular glandular 

 sac. The thick, strong, smooth, transparent sagittal muscles 

 of which it is composed run obliquely, longitudinally, and trans- 

 versely in fascicles interwoven into a net or trelliswork, and 

 one must admit that when the sac is seen in situ they might 

 easily be mistaken for spermatozoa. When, however, the sac 

 is ruptured, and the cirrus-pouch is isolated, the illusion is 

 dispelled, and their identity, by the cleavage of the fibrillae, 

 becomes apparent in contradistinction to the spermatozoa, which, 

 when the receptaculum is ruptured, protrude from the vesicle 

 in long, slender, tufted filaments or individuals. This sac is 

 0*167 mm. long and 0*102 mm. in diameter, but varies somewhat 

 in individual segments, as the longitudinal muscles have a 

 tendency to shorten, whilst the transverse lessen the diameter 

 of the sac. They are totally independent of the muscular 

 structure of the cuticle. This muscular sac contains two prostate 

 glands (Fig. 2). They are semi-lunar, and are developed simul- 

 taneously with the secretion of the spermatozoa in the vesicula 

 seminalis. The ducts of these prostate glands run upwards 

 to the apical end of the cirrus-pouch, to which they are attached, 

 and into which they pour their secretion. 



In the hermaphroditic segments the female genitalia are ventral 

 to the male. The vagina is cup-shaped ; its vaginal canal runs 

 obliquely upwards in the segment crossing the proximal ovary 

 dorsally. It then runs dorsally, curves at its distal extremity, 

 and, running proximally, swells out into a large pyriforin sac, 

 the receptaculum seminis (Fig. 12, ?*s). The ovaries are paired 

 organs, but dissimilar (Fig. 12, oo), the proximal being elongated, 

 whilst the distal is somewhat rosaceous. The yelk-gland is 

 orbicular (Fig. 12, yg), whilst the shell-gland is long and 

 attenuated. 



The uterus (Fig. 13) in some of my specimens had not developed, 

 and in those in which it had it was very immature, being only 

 formed at the proximal and distal lateral borders of the segment. 

 In a ruptured uterus which contained impregnated eggs I could 

 trace none which had advanced from the ovarian to the hexacanth 

 stage. 



