794 PROFESSOR J. STEPHENSON 



vi (i.e. the interval between septa 5/6 and 6/7). Its cavity is of considerable size, 

 and rather pear-shaped in outline ; it is filled with a clear homogeneous material, 

 staining slightly with eosin. The lining epithelium is columnar, the nuclei and 

 stainable protoplasm of the cells being situated peripherally, the greater part of the 

 cells being non-stainable and appearing to be filled with droplets of a clear, perhaps 

 mucous, substance. Outside the epithelium is a thin muscular layer ; and outside 

 this a layer of cells ("prostate") of large size, slightly staining, the cell-body having 

 a reticular structure ; this reticulum is the only thing which takes the stain, the 

 included spaces being quite clear. These cells are presumably not glandular, since 

 they belong to the peritoneal layer, and though sometimes attached by a tapering 

 stalk-like end to the atrial wall, do not, so far as can be seen, penetrate the muscular 

 coat to enter between the lining cells of the atrial chamber ; indeed, in many, perhaps 

 most, cases, they are, though adherent amongst themselves, distinctly separate from 

 the muscular coat. Moreover, similar cells are to be seen in clusters attached to the 

 inner surface of the body-wall near — especially just posterior to — the termination 

 of the male duct. These peritoneal cells over the atrium are arranged in small 

 clusters, which gives the surface of the atrium a lobulated appearance, and disguises 

 the proper pyriform shape of the chamber. The ejaculatory duct, short and narrow, 

 leaves the atrium ventrally ; the nuclei of its wall are closely crowded together ; 

 around its opening, as just mentioned, are groups of peritoneal cells attached to the 

 inner surface of the body- wall. 



The ovaries are in segment vi, in a position corresponding to that of the testes 

 in the next anterior segment. In the very early sexual specimen mentioned 

 previously they were smaller than the testes, and therefore probably appear after 

 them ; they were still present in one of the fully mature specimens, in which the 

 testes had disappeared. The ovisac, developed from septum 6/7, and enveloping the 

 hinder part of the sperm-sac, is single, and extends backwards for a distance which 

 varies in different specimens ; it may reach the level of the anterior part of segment 

 xi. No trace of ovarian funnels could be seen in any of the specimens. 



The s'pevmathecse are in segment v, with their external apertures between 

 segments iv and v. Each consists of a duct and an ampulla. The duct is vertical 

 or slightly oblique in position, cylindrical in shape, with a narrow aperture and 

 lumen, the latter lined by a small-celled epithelium with tightly packed nuclei. 

 The duct presents a characteristic appearance in specimens stained and mounted 

 whole, or in sections which cut the surface of the duct tangentially ; the nuclei 

 of the wall appear deeply staining, closely packed, and much elongated in a direction 

 transverse to the long axis of the duct. External to this epithelial layer is a stout 

 layer of circular muscular fibrils, without nuclei ; and this in turn is invested by a 

 few scattered small peritoneal cells, of which the oval nuclei are the most conspicu- 

 ous part. At its upper end the duct is invaginated upwards into the cavity of the 

 ampulla. The diameter of the duct is about 30 m. 



