518 RAYMOND PEARL. 



account of the movements of land plauariaus; in fact, by far 

 the best description of these phenomena in tlie literature. 

 In this account the relation of the movement to the mucous 

 secretion from the ventral surface of the body is brought out 

 in great detail. The principal factors in producing the 

 movement in the case of the land planarians he gives as 

 (a) ciliary movement on the ventral surface, {h) rhythmical 

 contraction waves passing longitudinally over the ventral 

 surface, (c) secretion of slime, and (d) snake-like movements 

 of the whole body. A comparison with the movements of 

 other planarians (fresh-water) is made. In this connection 

 it may be mentioned that Lehnert considered rhythmical con- 

 traction waves passing along the ventral surface of the 

 animal to be a factor in the movement of fresh-water 

 planarians (Den dro caelum lacteum, PI an aria poly- 

 chroa, and Polycelis tenuis). This I am unable to con- 

 firm from observations on the planarians which I have 

 studied. This point will be discussed more fully later. The 

 food and the method of taking food in case of the land 

 planarians, Lehnert worked out very thoroughly. They were 

 found to be carnivorous, and in the case of Bipalium the 

 pharynx was capable of being stretched over a large piece of 

 earthworm, so that it resembled a very thin transparent skin 

 covering it. The relations to other phases of the environ- 

 ment, e.g. air, water, tempei'ature, light, solid bodies, etc., 

 are described very briefly. 



Haspail ('98), in a brief note, mentions the feeding of a 

 planarian. 



Van Duyne ('00) mentions briefly the movements of 

 heteromorphic forms of PI an aria torva (?). He found 

 that the parts of two-headed individuals moved inde- 

 pendently of each other, and that each piece would move 

 away from the other until they had completely torn apart. 



Willey ('07j, in a brief note, describes the structure of a 

 remarkable asymmetrical planarian, for which he proposes 

 the generic name lIetero])lana, having the left side of the 

 body almost completely atrophied. Regarding the loco- 



