552 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
(figs. 11, 17 to 22). Under high magnifying power occasional nucleated 
cells are visible. The nerve vessels extend back through the body, one 
near each margin of the central core (figs. 19, 20, 32). They were 
observed in sections made near the middle of the strobile, where the 
genitalia had already begun to develop. No nucleated cells were 
observed in the posterior extension of the nerve vessels, where they 
appear to consist of spongy tissue alone. These vessels are without 
proper walls in any part of their course. 
Genitalia . — Along one of the lateral faces of each mature segment 
there is a depression, which is called in the explanation of the figures 
the lateral furrow (figs. 26, 27, 29, 30, 31). For convenience of descrip- 
tion, the face which bears the lateral furrow is called ventral and its 
opposite dorsal. 
The mature segments contain both sets of sexual organs. The ex- 
ternal aperture is a genital cloaca. It is marginal and situated in the 
elongated mature segments a little in front of the middle. The cirrus 
is long and apparently smooth, except at the base, where it is beset 
with short curved spines (fig. 12). The male genital organs consist in 
general of the cirrus, which, when invaginated, is coiled into several 
folds in the cirrus pouch. The latter, together with the voluminous 
folds of the vas deferens, lies towards the median region of the segment 
in the sinus formed by the vagina. The testes develop within the cen- 
tral core of the strobile. They consist of spheroidal, granulo nuclear 
bodies, often appearing as nests of nuclei, which occupy the whole inner 
core of the segment back to the germ glands, thus, in part, surrounding 
the cirrus pouch, vas deferens, vagina, and uterus, all of which lie in 
the central space, i. e., the space which is inclosed by the thin layer of 
longitudinal and circular muscles. 
The fine ducts which lead from the testes to the vas deferens have 
not yet been traced satisfactorily. A duct which is continuous with the 
voluminous folds of the vas deferens at the base of the cirrus pouch 
lies along the median line near the dorsal side of the segment (figs. 27, 
29, v. d.). 
The testicular lobes apparently communicate with this by means of 
fine tubules, but their disposition is not clearly shown in any of the 
sections. One of the lobes of the testis, in which there are spermatic 
cells and spermatozoa, is shown in fig. 39. 
The following points on the arrangement of the female genitalia 
have been elucidated: The vagina opens in front of the cirrus in a 
common cloaca (figs.* 34 and 35). Its course is thence forward and 
inward to the median line near the anterior end of the segment, thence 
posteriorly along the median line on the dorsal side of the uterus. 
Throughout its course it presents in sections a rugose interior surface 
(fig. 43). There are two enlargements of the cylindrical vaginal tube, 
one near the genital cloaca, from which the sketch shown in fig. 43 was 
made, the other near the posterior end of the segment in the midst of 
