108 MR. F. F. LAIDLAW ON POLYCLADS [May 26, 



The dimensions of an adult specimen are as follows : — 



Length 30 mm. 



Breadth 17 ,, 



" Mouth," from anterior end ... 14 „ 



cJ" aperture fi"om " mouth " ... 4 „ 



? „ „ male 1 „ 



This species externally bears a close resemblance to a typical 

 Leptoplana, being perhaps a trifle broader and more leaf-like. 

 Further, its intei-nal anatomy shows it to be distinctly related to 

 the members of that genus, but the presence of two vesiculfe 

 seminales with thick muscular walls is sufficient to distinguish it 

 from that somewhat crowded genus. The arrangement of the 

 eye-spots is shown in fig. 3, PI. IX. The pharynx is very large, 

 and extends for a distance of over 8 mm. The gut-branches are 

 numerous and without anastomosis. 



Genital AjJjxircitus. 



Male organs. — The two vasa deferentia each open into the hinder 

 end of the elongated and somewhat convoluted vesiculse seminales 

 (PI. IX. fig. 3, V.S.). These have thick muscular walls consisting of 

 circular fibres, amongst which are found a small number of oval 

 nuclei. The lumen is narrow, aiid lined with a flattened epithe- 

 lium. After running forwards for a total distance of about "75 mm., 

 the two vesicvilfe unite, and their lumen is continued backwards 

 into a median ductus ejaculatorius, which has a length of about 

 •5 mm. For the first part of its course it has thick walls, and its 

 diameter is about equal to that of either of the vesiculfe, whilst 

 the epithelium lining its lumen is apparently of a prostatic 

 character. For the last third of its course or thereabouts it 

 becomes much narrower, and has much thinner walls and the 

 epithelium loses its secretory chai-acter. Finally, this narrower 

 part of the median ductus, which lies through nearly its whole 

 leng-th at a level dorsal to the vesiculse, opens on to the base of a 

 small penis, which is armed with a downwardly-curved, back- 

 wardly directed stylet. The penis lies at the upper end of a 

 fairly long antrum masculinum. 



Female apparatus. — The female aperture opens into a wide 

 convoluted vagina, which at first has a course in general in a 

 forward direction, and is provided with rather thick walls, but 

 after a time its walls become thinner and the lumen wider. It 

 then turns backwards, lying dorsal to the first part of its course, 

 and becomes rather narrow, whilst the cells lining it, up to this 

 point ciliated, lose their cilia, and have rather the appearance of 

 secretory cells. When this backwardly-directed part reaches the 

 level of the female aperture, it receives the two uterine ducts 

 through a common opening on its ventral side, and is continued 

 beyond this to end in a small, slightly muscular accessory vesicle. 

 The shell-glands lie close about the aperture. 



