THE STRUCTURE OF CRYPTOGONIMUS 
531 
etal cells, measuring 0.006 mm., and have a very large nucleus 
(0.005 mm.) with membranes, granular chromatin and a large 
and distinct nucleolus, or in some cases the nuclear membrane is 
wanting and the chromatin gives indications of activity, in one 
case radially arranged cells are present but in the main the mate- 
rial is not favorable for study of spermatogenesis. 
It has not been possible to recognize the ducts leading from the 
spermaries to the very large seminal vesicle, either in living speci- 
mens or in preparations. The seminal vesicle is a very large organ 
occupying the dorsal region of the body in the space between the 
spermaries and ventral suckers. Figs. 2, .3 and 5 show its posi- 
tion. It has a winding course which produces the broken effect 
shown in figs. 2 and 3. The diameter of the organ varies some- 
what, it is about 0.05 mm. or less and is nearly uniform through- 
out. The wall is a thin sharp line, in which in places indications 
of circular muscle fibres are present. The organ is filled with 
spermatozoa in all cases which have come under my notice, 
showing that the spermaries must have been active recently. 
At its anterior end the cavity of the seminal vesicle suddenly 
narrows into a tube of a diameter of 0.01 mm. which bends sharply 
at a right angle with the seminal vesicle and passes in a ventral 
direction. This passage may be called the ejaculatory duct since 
it is surrounded by the prostate cells. It measures 0.02 mm. in 
length and 0.01 mm. across. Its wall is somewhat muscular. 
There are a few longitudinal fibres and a few circular ones; 
neither lie close enough together to make a continuous 
sheet of muscle. Figs. 5 and 6 show this duct and 6 gives a 
fairly accurate view of the musculature full}' corroborated by 
longitudinal sections of the animal. Anteriorl}' the ductus ejac- 
ulatorius passes into a chamber of the same size with which the 
uterus communicates and which may hence be called the atrium. 
Surrounding the ductus there are certain peculiar cells shown in 
the diagram, fig. 5. These cells are confined to this part of the 
body. They lie in a loose and open mass on each side of the duc- 
tus. In a cross section of the animal they show an arrangement 
as if radiating from the ductus. These cells present a globular 
free end in which a nucleus is seen surrounded by a small amount 
