H. A. Baylis 
411 
Excretory system. Of the two pairs of longitudinal vessels, the dorsal pair 
are very narrow, but thick-walled. They are usually situated vertically above 
the ventral vessels, but may be a little to either side of them. The ventral 
vessels are very wide. These, instead of being merely connected by a branching 
transverse vessel at each interproglottidal division, as in 0. zonuri , give off 
numerous small lateral branches, which ramify about and anastomose here 
and there, forming a complete network extending throughout the medullary 
parenchyme. 
Genital organs. Rudiments of the genital ducts are visible in almost the 
earliest distinguishable segments. Mature segments appear at about the 35th. 
The ovary (PI. XXI, fig. 6, Ov.) is situated almost in the centre of the segment. 
It consists of two large lateral portions connected by a narrower bridge, and 
the whole, when fully developed, measures from 0-23 to 0-25 mm. across at 
the widest part. Behind it is the yolk-gland (PI. XXI, fig. 6, Vit.), forming 
with the two lateral portions of the ovary, as Liihe (1898) remarks to be 
characteristic of the genus, very much the shape of a trefoil-leaf. Between 
the ovary and yolk-gland, on the dorsal side, is the shell-gland (PI. XXI, 
fig. 6, S.). 
The testes (PI. XXI, fig. 6, T.) are from 39 to 46 in number. In the 
best-preserved material (PI. XXI, fig. 6) they are arranged almost in a straight 
series of three to four rows across the back of the segment. They extend 
forward a little further at the sides than in the middle of the series, but not 
as far forward as the yolk-gland. In the other material (PI. XXI, fig. 7), where 
the segments have been much stretched in a longitudinal direction, they 
surround the yolk-gland in a horse-shoe pattern. This difference is probably 
sufficiently accounted for by the different states of contraction. The two 
figures referred to are drawn to the same scale, and the apparent difference 
in the size of the testes is due to one of the segments not being at quite such 
an advanced stage as the other. 
The genital ducts pass between the dorsal and ventral excretory vessels 
and dorsally to the lateral nerve. They open at the base of a large muscular 
genital cloaca (PI. XXI, fig. 6, Cl.), 0-15 mm. long. The cloaca has a narrow 
distal portion and a large proximal cavity, into which the fleshy cirrus pro¬ 
trudes from the cirrus-sac. The walls of the cloaca send out many radiating 
muscle-fibres to the subcuticular layer. The cirrus-sac (PL XXI, fig. 6, C.S.) 
is of an elongate pear-shape. It measures about 0*15 mm. in length and 0-08 
mm. in width at the widest part, which is nearest to the cloaca. The vas 
deferens (PL XXI, fig. 6, V.D.) is much coiled for the distal portion of its 
course. The vagina (PL XXI, fig. 6, Vag.) enters the genital cloaca behind and 
somewhat ventrally to the cirrus-sac. It forms a spindle-shaped swelling in 
its course before reaching the ovary, then becoming narrow again. Between 
the two lateral portions of the ovary it forms a coil functioning as a recep- 
taculum seminis. 
The uterus begins to appear at about the seventh mature segment. Its 
