ox SO^[E (,)UEEXSLAX1) TRE^^IATODES. 
381 
Tlie Nervous System is of the usual type, consisting of 
a large cerebral ganglion on eitlier side of the oesophagus, 
joined by a thick transverse commissure, and giving off a 
number of nerves besides the main, latei’al nerve-cords. The 
latter run backwards in the interval between the intestinnl 
limb and edg’e of .the body on each side, giving off’ nerves to 
various parts (fig. 37). 
Reproductive System. — In whole mounts the male 
and female ducts appear to open on the surface separately, 
but the sections show them opening into a shallow genital 
chamber (fig. 35), which lies laterally on the left side, outside 
the intestine. The testes are not only deeply lobed, but 
actually split up on each side into from four to six separate 
pieces, which meet in the middle line behind, so that the 
whole forms a U-shaped structure. The anterior pieces lie 
exactl}^ ventral to the intestinal limbs; posteriorly they 
gTadually converge on the middle line. The separate pieces 
are themselves deeply lobed. In whole mounts the separate 
parts, which are only connected by the ducts, overlap one 
nnother somewhat when viewed from the dorsal or ventral 
aspects, so that their separate identity is not quite apparent. 
The two vasa deferentia pursue a separate course forwards 
for some distance, and on meeting continue on as a single 
duct on the right side, between the uterus and the yolk- 
glands. The enlargement of this tube to form the vesicula 
seminalis occurs some distance behind the anterior end of 
the yolk-glands. The part of the vesicula seminalis lying in 
the region of the yolk-glands, the unpaired vas deferens and 
the separate right vas deferens are about equal in length, 
each lying near a third of the length of the yolk-glands. 
The vesicula seminalis is coiled throughout its whole length, 
the short part lying within the base of the cirrus sac, taking 
the form of an S-shaped curve. 
The cirrus sac is a strongly developed, elongated, club- 
shaped structure, with thick muscular walls, lying obliquely 
across the body in the hinder part of the anterior body third. 
There is a well-developed pars prostatica, marked off from the 
