TAPEWORM PARASITIC IN THE STICKLEBACK. 123 
walls consist of an inner ciliated epithelium—which appears to 
pass into the cuticle of the body—a muscular layer, and an outer 
epithelium ; altogether the wall is ‘0034 mm. thick, and the lumen 
of the tube -003 mm. dia. Along its course, but particularly near 
its opening to the exterior, are numerous glands, 004 mm. dia. 
at their widest part x ‘007 mm. long, with distinct nuclei, 
-0011 mm. dia., and having fine ducts opening into the lumen of 
the vagina. Just before it opens into the oviduct, the walls have 
a slightly different character. They diminish in width to 
0029 mm., the muscular layer nearly disappears, and the main 
thickness of the tube is due to a layer of cubical epithelium, 
similar to that lining the cavity of the oviduct. The opening of 
the vagina into the oviduct is very small. 
The ovary is two-lobed. The lobes are elliptical, and are 
joined anteriorly by a small common portion. Kach ovary is 
surrounded by a delicate membrane, which, according to 
Kraemer, passes into the sheath of the oviduct. The ovary is 
usually so full of eggs that their shape is changed by compression 
from spherical to polygonal. They will be deseribed later in 
connection with the life-history. 
Text figure 4. 
o.d. 
O.C. 
Diagram of the female genital ducts. 0.c., odclapt; o.d., oviduct; o0.¢., odtype ; 
0.v., ovary; v., vagina; 2.d., vitelline duet; v.d.’, common vitelline duct; 
u., uterus. 
Leading from the connecting-bridge of the ovaries is the 
odclapt or “Schluckapparat ” (PI. Il. fig. 14). This is a nearly 
spherical muscular organ, -002 mm. broad x ‘0022 mm. long, 
with a lumen of 008 mm. dia. Its cavity is lined by cubical 
epithelium according to Benedict, but with simple cuticle 
according to Kraemer ; the latter is the case with my specimens. 
The muscular band surrounding it is hemispherical in transvere 
section and constitutes the greater part of its walls. An irregular 
ring of nuclei surrounds it externally. 
Into the odclapt opens the oviduct. This is a short tube 
