312 MR. F, F, LAIDLAW ON THE al Apri2it, 
there may be four or even six penes present. In another genus 
presumably allied to this, viz. Polypostia Bergendal [1], the penes 
lie in large numbers around the female aperture. 
The female apparatus is no less remarkable than that of the male. 
The vagina (va.) runs forward for some little distance from the 
aperture, then turns upwards. As it does so, it is twisted into 
a remarkable spiral coil, making some five complete turns. . It 
then runs backwards, narrows considerably, and soon receives the 
openings of the two uteri (wt.) on its ventral side. Beyond this 
point it is continued back as a narrow accessory vesicle (acc.ves.) 
about as far as the level of the female aperture, when it turns 
sharply ventralwards and opens to the exterior by the antrum. 
The only other Polyclads with which I am acquainted that 
possess a secondary female opening are Zrigonoporus of Lang [6] 
and Polyporus of von Plehn [11], but in both these cases the 
second opening is quite distinct from the primary one (the true 
antrum femininum). 
The curious spiral twisting of the vagina in the present species 
is, so far as I know, unparalleled in the order. 
For the first part of its course, 7. ¢. whilst it is running forwards, 
the vagina is lined with elongated columnar ciliated cells, the nuclei 
of which lie near their bases. Outside this epithelium is a thin layer 
of circular muscle-fibres, and beyond these, in my sections, can be 
seen a great number of nuclei massed round the vagina, and 
probably belonging to gland-cells. Where the vagina turns 
dorsalwards and becomes spirally twisted it has narrowed slightly, 
but its epithelium retains the characters already mentioned. The 
muscle-sheath does not follow the individual folds of the spiral, but 
forms a continuous covering for that part of the duct (Pl. XXIII. 
fig. 6, m.s.). The rest of the terminal female ducts are precisely 
similar in character to the first part of the vagina, only narrower. 
There seem to be no special shell-glands present. 
The genus may be defined as an Acotylean genus in which behind 
the functional penis a small second penial organ occurs. The 
accessory vesicle of the female apparatus opens to the exterior 
through the antrum femininum. Body pointed at either end. 
Marginal eye-spots present ; mouth subcentral. 
Family LArocestipa. 
LATOCESTUS ARGUS, Sp. n. 
Four specimens were collected by Mr. Evans. One of these is 
labelled ‘‘ Chocolate-brown above, slightly lighter below.” 
The largest specimen has a total length of about 30 mm. and a 
breadth of 5mm. The mouth is 2°5 mm. from the hinder end of 
the body. 
This species is proportionately longer than the other member of 
the genus which I have had an opportunity of examining. Its 
most striking feature is the presence of a crowded row of eye- 
spots running completely round the margin of the body. The 
