1903. ] POLYCLADS OF THE ‘‘SKEAT EXPEDITION.” 305 
inner walls of the prostate chambers. Between each of these 
chambers a fine double septum runs out from this inner wall (Plate 
XXIII. fig. 2, s.). The prostate cells stain very feebly, and the 
lumen of each chamber is well defined, and contains in most cases 
a certain amount of secreted matter. Outside the chambers is a 
fairly thick layer of circular muscle-fibres, and, beyond these, an 
ill-defined layer of cells which appear to be glandular. Here 
and there are faint indications of processes from these outer 
glandular cells, piercing the muscle-layer of the prostate organ. 
This muscle-layer is also traversed by processes from the septa of the 
chambers. There is no longitudinal muscle-coat to the prostate. 
Towards the level where the prostate-chambers open into the 
ductus ejaculatorius, some of them open into each other, so that 
the number of chambers seen in cross-section is reduced to four 
or five. 
On the proximal, hinder, side of the prostate, the ductus is 
continued back into the vesicula seminalis (v.s.), which is long and 
contorted. It is lined with a ciliated epithelium, and its walls are 
composed of regularly arranged circular muscle-fibres. At its 
extreme hinder end it turns sharply forward and ends blindly. 
Just before it takes this turn forward, the two vasa deferentia 
open into it, one on either side, after piercing through its 
muscular wall. 
There is a spacious antrum femininum surrounded by the large 
shell-glands, the secretions of which it receives. The vagina leaves 
the antrum dorsally, and runs forward for the first part of its 
course through the shell-glands, the secretion of which it also 
receives. It then turns first dorsalwards and then backwards, 
acquiring in its course a fine wall of circular muscle-fibres. After 
running back for a short distance, it receives the short common 
duct from the two uteri. It then continues to run back as far as 
the level of the antrum femininum, where it ends blindly. 
It is evident that this species is closely allied to von Plehn’s 
Plagiotata promiscua [7]; in fact, the terminal parts of the male 
apparatus in the two species have almost identically the same 
structure, 
It differs from von Plehn’s speciesin having the pharynx of the 
normal type, not elongated transversely. This character is of 
sufticient importance to justify the placing of these species in two 
separate genera. In addition Wotoplana is characterised by 
differences in the female apparatus, and by the great length of 
the antral chamber of the male organ. 
The genus Votoplana may be defined, then, as follows :-— 
A Planoceroid genus with styliform penis and without a bursa 
copulatrix. The male antral chamber is very long; there is a 
complicated prostatic organ consisting of several chambers lying 
around the ductus ejaculatorius in front of the vesicula seminalis. 
The latter is long and twisted. Body rather elongate, without 
marginal eyes ; mouth-opening rather behind the middle ; pharynx 
normal ; gut-branches numerous, without anastomosis. 
20* 
