MOVEMENTS, ETC., OF FRESU-W/Vl'ER PLANA HIANS. 535 



tlio animal to the film, the surface tension being sufficiently 

 great to support a considerably greater weight than that of 

 a flat- worm. 



It is interesting to note in this connection that the land 

 planarians are able to move about on the top of the surface 

 film of water to a limited extent (cf. Lehnert, loc. cit., 

 p. IG). The immediate means of support here, as in the case 

 of the fresh-water planarians, is the mucous secretion. 



The leaving of the surface film by means of the mucus 

 thread described above apparently does not take place if it is 

 possible for the same result to be accomplished in any other 

 way. Before it occurs the worm usually stretches the 

 anterior end down into the water, and turns it in all direc- 

 tions. If it comes in contact with something solid the 

 anterior end becomes attached to this, and pulls the posterior 

 end of the body away from the film. If nothing solid is 

 within reach the worm Avill usually, after a time, drop down 

 on a mucus thread as described. 



III. Food. 



Planarians will take almost any sort of animal food very 

 readily, I have used mainly, in the feeding experiments, 

 crushed pieces of fresh-water molluscs, such as Physa, 

 Planorbis, etc. One of these molluscs, removed from the 

 shell and placed in a dish centainiug a large number of 

 planarians, will, in a short time, be literally covered with the 

 worms feeding. If a worm is gently lifted off the ])ile the 

 greatly stretched pharynx will bo brought into view. The 

 worms will eat any other kind of animal tissue (fresh meat, 

 parts of insects, pieces of fresh-water worms, etc.), so far 

 as I have observed, tlu; only condition being that the meat 

 must be fresh. As will be shown latei", the juices from the 

 food act as chemical stimuli, so that it is necessary that the 

 tissue be crushed or bruised so that its juices can escape into 

 the water. A pai'tially crushed specimen of PI an aria, even 

 though still able to move about, will be seized upon and eaten 



