64 H. G. Krihs 



right angles to the body, then a sudden turn is made away from 

 the stimulus. With a lateral application to the prostomium the 

 head is not turned toward the pipette before the negative reaction 

 takes place. Application at the posterior papillae stimulates a 

 quick contraction of the posterior segments and a rapid crawling 

 movement forward. Lateral body stimulation follows the same 

 rules as under normal stimuli, only the reactions are far more ener- 

 getic. Not infrequently the first contraction will throw out many 

 oil globules, etc. Movement away in this case is through a spiral 

 twisting reaction. 



Organic acids were similar in effect to the mineral acids. 



Alkalies. All reactions were in the shape of energetic contrac- 

 tions of the body, away from the stimulus when applied to the 

 ends of the body, with the bulge towards the stimulus in response 

 to the lateral exposure. The animals were powerless to make any 

 further effort to leave the field of stimulation although they 

 recover rapidly from the shock. The muscles of the body wall 

 facing the pipette seem to be paralyzed by the chemical as that 

 side seems passive in the movements that soon follow. These 

 movements are an alternate contraction and extension of the mus- 

 cles of the body wall opposite to the place of stimulation. 



Halides. There is a prompt negative reaction when these are 

 applied to the head and the animal is usually able to get away 

 from the stimulus. This is not the case when the caudal end or 

 side is stimulated. When stimulated at the side the first contrac- 

 tion is followed by increasingly large peristaltic waves running 

 from pharynx to papillae, which effectively inhibit any locomotor 

 movements. With the bromides at the papilla?, the papillae are 

 quickly stuck to the substratum while the anterior parts twist and 

 writhe in all directions. With the chlorides a forward contraction 

 may advance the animal a little, but it soon loses power of orien- 

 tation and lies at the mercy of all sorts of muscular contraction 

 and extension. 



Sulphates. The reactions to FeSO^ were similar to those with 

 the halides. CuSO^ and ZnSO^ had the same effect as the acid 

 solutions. 



All of the chemical solutions under this category had the further 



