THE MARINE TURBELLARIA. 



293 



uf V 



Genital apparatus of Pericelis byerleyana (diagrammatic). 

 For explanation of lettering see text. 



The penis is muscular and directed backwards. It is conical in shape, and tapers to a 

 fine point, which projects into a long and extremely narrow antrum masculinum (a. m.). At 

 its anterior, proximal end the penis re- 

 ceives on either side the vasa deferentia 

 {d. e.), crowded in the specimens with 

 spermatozoa. 



Female apparatus. The shell- 

 glands are large and extend for a con- 

 siderable distance laterally. Their secre- 

 tion is in the form of an immense 

 number of minute, spindle-shaped, 

 rhabdite-like bodies, which are each 

 about a quarter of the size of the 

 epidermal rhabdites. These are of pe- 

 culiar interest as bearing on the morphology of the rhabdites of Turbellaria, and strongly 

 supports the view taken by Wood worth [19] and others. 



The vagina is narrow and lined with ciliated epithelium, surrounded by a very narrow 

 layer of circular muscle-fibres, thicker at its hinder end, where it turns downward to receive 

 the uteri the vagina has rather a thicker muscle layer. Outside the muscle-fibres lie a number 

 of nuclei probably belonging to gland-cells. The epithelial lining of the uteri, if present, is so 

 reduced that I have not been able to distinguish it. The walls of the uterus apparently 

 consist of a ring of muscle-fibres surrounded as in the case of the vagina with gland-cells 

 (see fig. 16). The uterine vesicles (see Fig. 65, xit. v.) are lined with a cubical, or somewhat 

 columnar, non-ciliated, secretory epithelium. It rests on an extremely delicate basal membrane, 

 and there is no muscular coat. The character of the lining epithelium of these vesicles recalls 

 that of the receptaculum seminis of Planocera langii. 



The vesicles are connected with the uteri by ducts of varying length, some so short 

 that the vesicle is almost sessile on the uterus (fig. 15). They are similar in structure to 

 the uteri themselves but smaller. The vesicles are fairly numerous, eleven opening into the 

 uterus of one side between the level of the mouth opening and the vagina. So far as I can 

 find they do not extend forward in front of the mouth. As already stated these vesicles 

 firequently contain spermatozoa, surrounding a ' lump ' of material, which appears to consist 

 of small, round, hyaline cells with black nuclei, which do not resemble eggs. In the homologous 

 vesicles of Diposthus corallicola Woodworth and in certain Euryleptidae spermatozoa are found 

 surrounding fragments of what Woodworth and Lang suppose to be eggs, but in the present 

 instance these ' lumps ' are certainly not fragments of eggs. The ovaries contain ripe eggs. 

 The oviducts themselves are indistinguishable. 



Certain remarkable structures, as has already been stated, occur in connection with the 

 uteri which bear a fairly close resemblance to the yolk-glands of certain Tricladida. The only 

 structure with which they can be compared in the Polyclads are the ' rosette-like glands ' of 

 Cycloporios papillosus, described by Lang [9]. These differ firstly in that they open into the 

 oviducts, and secondly in having the character of glandular diverticula fi"om the oviducts. In 

 Pericelis on the other hand there are numerous gaps in the walls of the uteri (PI. XX. figs. 15 and 

 16), through which project deeply staining pyriform cells, which do not seem to be of a definite 

 secretory or glandular character, with oval black nuclei. On the whole these organs of Pericelis 



