8 PLATYIIELMINTHES TURBELLARIA CHAP. 



Like all Polyclads, Leptoplana is marine. It is probably found 

 on all European shores, northwards to Greenland and southwards 

 to the Red Sea, while vertically it ranges from the littoral zone 

 down to fifty fathoms. There is, however, an apparently well- 

 marked difference between the littoral specimens, which vary 

 from three-quarters to one inch in length, are brownish in colour 

 and firm in consistency, and the more delicate examples half an 

 inch long, white with a brown tinge, which occur in deeper water. 

 At low water Leptoplana may be found buried in mud or on 

 the under surface of stones, in pools where darkness and damp- 

 ness may be ensured till the return of the tide. It is, however, 

 by no means easy to detect and remove it from the encrusting 



FIG. 2. Leptoplana tremdlaris. Three-quarters view from the ventral surface. The 

 pharynx (ph) is widely protruded through the mouth (mo) as hi the act of attack- 

 ing prey, br, Brain with nerves, close to which are the four groups of eyes ; mg, 

 stomach ; mgc, " marginal groove " ; pe, penis ; sc, sucker ; ttt, uterus ; vd, vasa 

 deferentia ; 9, female genital aperture surrounded by the shell-gland ; <J , male aper- 

 ture. (Semi-diagrammatic, and x 6.) 



Polyzoa, Ascidians, or Sponges with which it is usually associated. 

 The flat, soft, unsegmented body is so closely appressed to 

 the substratum that its presence is usually only betrayed by its 

 movement, an even gliding motion of the mobile body, which 

 suggested the apt name " la pellicule animee " to Dicquemare. 

 The creeping surface is called ventral, the upper one dorsal, and 

 as the broader end of the body always goes first, it is anterior as 

 opposed to the more pointed posterior extremity. With a lens 

 the characters shown in Figs. 1 and 2 may be observed. The 

 eyes are seen as black dots near the anterior end, and are 

 placed at the sides of a clear oval space, the brain. Along the 

 transparent margin of the body, the ends of the intestinal 

 branches may be seen. These ramify from a lobed stomach or 

 main-gut, and should the specimen be mature, the " uterus " loaded 



