26 H, N. MOSELEY« 



cavity or sheath with a strongly muscular wall, by contraction 

 of which the organ is protruded^ and which is in connection 

 above with the sheath of the pharynx. Branched retractor 

 muscular fibres are attached to the penis, taking origin from 

 the sheath walls. The penis consists of a cavity with a mus- 

 cular wall and a thick lining of horny prickles, which are, 

 of course, on the exterior when the organ is protruded. This 

 horny layer does not readily transmit light, hence the area 

 occupied by it appears dark in the drawing. The cavity of 

 the penis leads by a tortuous canal, which lies over the uterus 

 for some distance to the anterior generative opening. 



The female organs consist of a uterus, ovaries, oviducts, 

 and albuminiparous glands. 



The uterus is an ovoid chamber, with muscular walls, 

 situate just posteriorly to the penis sheath. It opens by an 

 oval aperture towards its posterior part. This aperture may 

 be seen to gape widely open and again contract from time to 

 to time as the animal is under observation in the living state. 

 The ova are dispersed over the central region of the body, 

 round the pharynx and ganglia, as shown in fig. 9, as in 

 Leptoplana tremellaris, and other forms. Stretching up 

 on either side of the sheath of the mouth and that of the 

 penis from the direction of the uterus are a pair of organs, 

 which cross the vasa deferentia on their dorsal aspect. These 

 organs consist of a series of cells or sacs with well-defined 

 Avails filled with ova. They evidently correspond to the 

 loncy tubular organs in Leptoplana teremellaris, which is 

 called uterus by Keferstein (' Beitrage zur Anatomic und 

 Entwicklungsgeschichte einiger Seeplanarien Abhandlungen 

 der k. gessellschaft der Wiss zu Gottingen,' 1868, p. 27). 

 The organ corresponding in Leptoplana to what is here 

 termed uterus is called by Keferstein " Weibliche Geschlechts 

 Atrium." This organ is, however, certainly the homo- 

 lo"-ue of a corresponding mesially placed musclar organ 

 in Bipalium, which is connected by long and slender 

 ducts, with an ovary situate far off" in the head. In Bipa- 

 lium the organ could hardly be termed anything else but 

 uterus ; it receives here as in Stylochics pelagicus and 

 Septoplana tremellaris the albuminiparous glands, first 

 described as such by Keferstein, and its function Avould 

 appear to be the reception of ripe ova, and their preparation 

 by addition of albumen and shell for extrusion, which is 

 just the function of a uterus. The organ has been usually 

 termed uterus by anatomists, and there would seem to be 

 nothing to be gained by changing its name. The whole 

 difficulty arises from the fact that ova are scattered about in 



