288 



F. F. LAIDLAW. 



Average length about 48 mm. Eyes distant 10 mm. from the anterior margin. Mouth 

 opening about 20 mm. from the anterior margin. The male aperture lies about a millimetre 

 in front of the female, the latter is about 15 mm. from the hinder end of the body. 



The colour (in spirit specimens) is pale yellow. On the dorsal surface this is thickly 

 studded with rosette-like clusters of brownish-black chromatophores. On the mid-dorsal line 

 in the middle third of the back these chromatophores form a continuous band ; near the 

 margin the clusters are replaced to some extent by single chromatophores. 



The eyes are arranged in two clusters of ' tentacle-eyes ' of moderate size, each containing 

 about a score of eyes. In front of them lie on either side about as many more eyes 

 scattered irregularly. The gut branches anastomose. 



This interesting species combines to some extent the characters of Discocelis with those 

 of Leptoplana. The presence of a pair of receptacula seminis developed from the accessory 

 vesicle of the vagina resembles the condition found in Discocelis tigrina, whilst the absence 

 of marginal eyes and the widely separated gonopores forbid us to refer it to that genus. On 

 the whole it is most conveniently placed in the genus Leptoplana as at present constituted, 

 the male organs resembling those of other species of that genus. 



Female apparatus. (See Figure 63.) The vagina (va.) runs back from the female 

 aperture ( $ ) and receives the common duct {c.d.) from the uteri. 



These latter extend forward from the short common duct, each being formed of two 

 distinct sections. Firstly there is a duct-like part, 

 consisting of a narrow tube lined with cubical, cili- 

 ated epithelium, suiTounded by a few circular muscles 

 (u.d.). This opens at about the level of the male 

 aperture into a wide, irregular, glandular part, the 

 pair extending forward on either side of the pharynx, 

 and in one of the specimens, examined by sections, 

 containing eggs. The walls of this glandular part 

 (u.gl.) are much folded, and their epithelium is se- 

 creting actively and full of globules of a finely 

 granular substance. Cell outlines are not visible. 



Behind the entrance of the common duct from 

 the uteri the vagina, whose lumen is lined by cubical, 

 ciliated epithelium surrounded by circular muscle 

 fibres, runs back for a short distance, and finally 

 opens into a crescentic accessory vesicle (ace. v.) with 

 its horns directed forward. From either horn a narrow 

 duct (ace. d.) runs forward, ending in a spherical 

 dilatation {r. s.) which probably functions as a re- 

 ceptaculum seminis. The cubical epithelium, lining the accessory vesicle and the ducts opening 

 into it, is not ciliated. In one specimen the receptacula are crowded with spermatozoa, 

 surrounding a pass of what appears to be a granular secretion. 



Considerable interest attaches to this species in that the walls of part of the uteri 

 themselves are glandular. Glands in connection with the uteri are as a rule only present 

 in certain Cotylea, such as Diposthus, Pericelis and various Euryleptidae, where they occur in 



ace d 



Fig. 63. Female apparatus of Leptoplana pardalis 

 (diagrammatic). For explanation of lettering see text. 



