32 BULLETIN OF THE 



considered as vesiculse seminales. In Polyclads and in Rhabdocoeles a 

 vesicula seminalis is present. This organ has been described for land 

 planarians by Moseley ('77, p. 278) and Loman ('87, p. 81), and Kennel 

 ('88, p. 460) speaks of " mehrfach gewundenen Samenblasen " in Pla- 

 naria alpina. There can be no doubt that the terminal enlargements 

 found in Phagocata are a provision for the storage of a great number of 

 spermatozoa, as their size is found to vary in different individuals and 

 on different sides of the same individual according as the number of 

 spermatozoa is large or small. 



Thejomts orintromittent organ is a highly muscular plug-like structure 

 (Plate IV. Fig. 42, pe.) that lies in the genital atrium or penis sheath. 

 It is covered with a flattened epithelium, under which there are alter- 

 nating layers of circular and longitudinal muscles, five of each, form- 

 ing a thick zone. Immediately outside the epithelial lining of the tube 

 there is a band of circular muscles, and between these and the outer 

 muscles there is a broad zone occupied by a meshwork of muscular fibres, 

 prominent among which are those having a radial direction. The lumen 

 of the penis is not of an even calibre, but consists of a succession of 

 chambers, or dilatations, lined with a granular epithelium, which is 

 probably glandular. It is within the lumen of the penis, no doubt, that 

 the spermatophores are formed. The sheath of the penis is lined with 

 an epithelium of cylindrical cells, the nuclei of which lie close to the 

 bases of the cells, and are stained deeply, while the glandular cell 

 substance is stained only slightly. These cells also may be glandular, 

 but if so, I can find no explanation for their faint reaction with staining 

 reagents. In that respect they differ from all other glandular tissue. 



The female sexual organs consist of a pair of ovaries with their 

 oviducts, the vitellarium or yolk gland, the uterus, and the vagina. 

 The single pair of ovaries is situated in the anterior part of the body 

 a little behind the brain mass. They are symmetrically placed on 

 the ventral side of 'the body just dorsad of the main nerve trunks, 

 one on either side. They a])pear as rounded sacs filled with ova 

 (Plate II. Fig. 21). The wall of the ovary is a delicate membrane, 

 in which I could detect no sign of cell structure, such as Moseley ('74, 

 p. 137) found in the ovary of land planarians. Scattered in between 

 the ova are the nuclei of a connective-tissue network that fills the spaces 

 between the ova (Plate II. Fig. 21, nl. corit. lis.). lijima ('84, p. 412) 

 considers the branching cells between the ova as rudimentary egg cells, 

 at whose expense the ova develop. I have not yet seen different stages 

 in the development of the ova. 



