-30 Art. 3.— T. Kaburaki : 



trunks on the ventral side, while tliey run in Kct. Urmili just out- 

 side the latter. Generally the two vasa deferentia pursue a some- 

 what winding course, gradually widening as they proceed, and 

 finally uniting in the upper part of the penis-bulb. In their 

 -course they are always filled up with spermatozoa and thus are 

 sharply marked off from the surrounding tissues. 



The inner wall of the vas efferens and deferens is formed b}^ 

 a single layer of definite epithelial cells which are usuall}^ cubic or 

 flattened, and the protoplasm of which is very finely granular, but 

 not vacuolated. As usual, the epithelium exhibits at intervals 

 some ovoid nuclei deeply stainable. No trace of cilia could be 

 detected at points of exit for the vas efferens from the testis. 

 Directly external to the epithelium is a delicate layer of circular 

 muscular fibres. 



Penis. — The penis consists of the bulbous part and the 

 conical intromittent part which is vertically or subvertically dis- 

 posed in the penis-sheath. No chitinous stylet is present at all. 

 The bulb is comparatively less developed in the species examined 

 than in any freshwater planarians. 



In Pr. lactea (Text figs. 1, 4.) the vasa deferentia unite in the 

 penis bulb into a slender duct, the ejaculatory duct, which opens 

 at the tip of the penis, without assuming the character of widen- 

 ing, much as in Pr. ulvae. In St. trlgonocephala (Text fig. 2, 5) 

 they fuse in the blub to form a single slender duct, the vas 

 deferens impar, which stands in connexion, as in Pr. jaqueii, 

 with a moderately distended and smooth-walled vesicula; the 

 vesicula graduall^y narrows into the ejaculatory duct as it proceeds 

 towards the apex of the penis. Such similar feature are also found 

 in PJct. llmuli. Beyond the point of union of the vasa deferentia, 

 -a short common duct enters at once into a wide lumen which is, 

 however, more or less narrow as compared with that of the prece- 

 ding species. 



The lining of the penis lumen is an epithelium composed of 

 •cuboidal or cylindrical cells. As is well known, embedded in the 

 parenchyma around the penis are a number of the glands which 

 •open into the penis-sheath over the surface. Directly external to 



