354 DR. A. E, SHIPLEY ON [Mar. 16, 
reproductive pore is on one side of the body throughout its entire 
length, but in others, and rarer, it changes over and having been 
for the anterior half of the body on the right side it suddenly 
passes to the left and remains there till the end. 
The number of the proglottides varies with the length of the 
worm. An average-sized specimen would have between 250 and 
400 proglottides ; each of these might contain, say, a couple of 
hundred eggs. These figures, though necessarily rough, give some 
idea of the number of ova a single tape-worm may contain at any 
one moment. But mature proglottides are always breaking away 
and fresh ones are always being formed, like a recurring decimal, 
so that the number of ova a tape-worm produces in the course of 
its life is very much greater than the number it contains at any 
one moment. 
Although the male and female reproductive openings are close 
together, the male orifice is very clearly anterior to that of the 
female. It leads into a muscular protrusible penis, which was in 
all cases retracted. The penis ends in a much coiled vas deferens 
which runs half across the proglottis near and slightly obliquely 
to the anterior edge ; here it ends in a number of diverticula which 
form the testes. These are scattered through the parenchyma. 
The wall of the vas deferens is thin, its lumen is spacious, and it 
acts as a vesicula seminalis. The lumen is lined by a thin cuticle, 
and outside this and all around it are a number of spherical or 
oval cells which without exactly forming an epithelium probably 
secrete the cuticle. 
The vagina opens immediately behind the vas deferens. Its 
outermost part is thick-walled and the lumen contains some 
homogeneous substance which stains deeply ; further on the wall 
becomes thinner, the lumen more capacious, and here masses of 
Spermatozoa are to be seen. The ovaries are two, right and left, 
each rather of a cauliflower shape; they contain rounded ova in 
which besides the nucleus a second deeply staining body is some- 
times seen. The vagina makes a turn through about a right 
angle, and passing between the two ovaries, where it receives the 
two oviducts, it travels back to the vitellarium, a somewhat 
pyramidal body lying close to the posterior end of each proglottis. 
Certain unicellular glands in this region of the female duct are 
probably shell-glands, 
There seems to be no walled uterus, but the fertilized ova are 
scattered throughout the body embedded in the parenchyma. 
Each is a large oval cell with very vacuolated protoplasm and a 
nucleus at one side and numerous yolk-granules (Pl. LEX. fig. 12). 
Monticelli describes the proglottides as longitudinally striated, 
and the striations as due to the longitudinal muscles. These are 
certainly conspicuous in section, although in our specimens the 
external striation was not very well marked. 
One striking feature of D. wrogalli is the great extent to which 
the water vascular system is developed. It is spacious and large 
in the anterior segments, but in the posterior half of the body it. 
