376 
ED^ IN LINTON 
sperm-sac to the genital pore. In living worms it was noted that 
the sperm-sac often lay behind the eyes on the middle line in such 
position that it and the eyes formed an equilateral triangle. The 
sac is usually pyriform. Inside dimensions of a living specimen: 
length 0.048; breadth, at dorsal end 0 051, at ventral end 0.034. 
In this case it was noted that the walls of the sac were clearly 
limited on the inner side, but not so clearly defined on the outer 
side. Its walls are rather thin, but they become thick and mus- 
cular where they merge into the penis sheath. In life the sac is 
actively contractile. On one occasion a curious behavior of the 
sperm-sac was noticed. An ovum, with two large, clear germ cells 
embedded in a mass of yolk, lay just behind the sac and touching 
it. The o\aim was constricted in the middle where it was in 
contact with the sac and the two germ-cells had passed one to 
each side of the sac (figs. 37, 38). At the posterior border of the 
sac there was a wisp of fibers as though sperm were being forced 
into the o^Tim. At the same time there was an almost rhythmical 
contraction of the posterior border of the sac. The OM.mi was also 
contracting somewhat rhythmically. In another specimen the 
sperm-sac, which w^as collapsed and pushed to one side, appeared 
to be trying to approach one of the densely granular ova which 
was lying adjacent to one side of the worm. This ovum had one 
large, clear germ-cell, and was actively contractile. The impres- 
sion made on the mind by this behavior was that something of 
the nature of copulation was in progress (fig. 39). This singular 
action did not appear to be due to pressure of the cover-glass. 
In one specimen a cluster of spermatozoa was noticed on the 
median line a short distance behind the sperm-sac. The genital 
pore lay between the sac and the cluster of sperm. Similar clus- 
ters of sperm were seen in sections in a duct which lies posterior 
to the sac and leads dorsad to the volk-forming cells of the ovary 
(fig. 40). 
The testes were not satisfactorily made out. In a series of 
horizontal sections, made from a specimen which had been fixed 
in corrosive-acetic and stained with hsematoxylin and orange G, 
branching glands near the dorsal surface (fig. 8) were at first taken 
■to represent the testes, but are evidently vitellaria. In a young 
