THE MARINE TURBELLARIA. 289 



diverticula from the uterus. The accessory vesicle on the other hand only occurs in the 

 Acotylea. In Discocelis it is glandular. 



Male apparatus. The vasa deferentia dilate at their terminations to form a pair of 

 moderately wide vesiculae seminales whose walls are surrounded by a thin layer of circular 

 muscle-fibres. These vesiculae open into a short and narrow ductus ejaculatorius (PI. XV. 

 fig. 14, d.e.) lined with ciliated epithelium and provided with rather thick muscular walls. 

 This duct narrows suddenly as it enters the muscular penis (pe.), which projects as a bluntly 

 conical muscular mass into the antrum {a.m.). The antrum is lined with non-ciliated 

 epithelium and its walls are muscular, forming the muscle sheath ; I can find no trace of 

 gland-cells in the epithelium. 



Amongst the six specimens of this species collected at Minikoi is one which differs from 

 the rest in coloration, being much darker. After a careful examination I have come to the 

 conclusion that this difference is chiefly due to the expanded condition of its chromatophores, 

 though they may be slightly more numerous. Unfortunately it is not possible to say whether 

 this specimen was collected under different conditions from the others. Since examining these 

 specimens I have received from Mr Gardiner three others, which I believe to be specifically 

 identical with them, from Funafuti in the Pacific. 



4. Leptoplana, sp. 



One specimen from Minikoi. Damaged. 



The arrangement of the eye-spots is that of a typical Leptoplana. There are a pair of 

 small compact ' tentacle-eye '-groups, and in front of these the scattered brain-eyes. 



G-enital apparatus. The female aperture lies about two mm. behind the male, un- 

 fortunately the hinder part of the female apparatus is missing, but it bears a fairly close 

 resemblance so far as can be determined to that of L. vitrea as figured by Lang. The shell- 

 glands are very numerous, their secretion takes the form of enormous numbers of minute 

 rhabdite-like bodies, similar to those found in Pericelis (see below). These rhabdites can 

 be seen making their way into the lumen of the vagina. In the neighbourhood of the 

 terminal parts of the genital apparatus the unripe shell-glands are so numerous as to give 

 the tissue a characteristic appearance. They resemble closely those of L. alcinoi figured by 

 Lang ([9] T. 14, Fig. 2), but in the latter species they a.re pyi-iform, whilst in the species 

 under consideration they are spherical. 



As they ripen and become filled with the small rhabdite-like bodies, the cell outlines 

 become obscured, and finally the cells seem to disappear as though they had ruptured to permit 

 of the escape of the contained rhabdites. 



The walls of the vagina are lined with ciliated epithelium, and, as it passes back from 

 the antrum, a fairly strong muscle layer developes about it. After running for a short distance 

 backwards the vagina turns upwards and a little forwards and then finally backwards, receiving 

 the separate openings of the uteri. Thence it continues back, first as a narrow tube, but 

 further back appearing to open into a wide accessory vesicle ; owing to the displacement of the 

 organs at the hinder end of the body it is extremely difficult to follow. The uteri run 

 forward, and for the first millimetre or so of their length have muscular walls, further on 

 the muscles disappearing. 



37—2 



