686 



KAYMONI) PRARL. 



tlie body IS ap])roximately at rio-lit angles to the direction of 

 tlie current, may be described first. If a number of speci- 

 mens are sliding about at the nonnal rate, and a current of 

 from weak to medium intensity is made throug-h the prepara- 

 tion, the first reaction of all the specimens is to stop their 

 forward motion, turn towards the kathode, and start c ra wl i n g 

 very slowly towards this pole. The orientation towards the 

 kathode is at the first trial usually rather precise. The whole 

 animal gets squarely into line with the current and moves 

 slowly towards this pole. While the current is acting the 

 anode end of the body, in this case the posterior end, i-emains 



+ - 



3 + 



Fig. 42. — Diagram sliowinnf tlie typical elect rot actio read ion of Plauaria. 

 a. Position at the moment of making the current. !>, c, and ih Suc- 

 cessive phases of the reaction. 



rather strongly contracted, presenting the same appearance 

 as when mechanically stimulated. Movement occurs only for 

 a short time after the current begins acting. The worm soon 

 comes to rest, and further stimulation serves only to cause 

 contraction of various parts of the body without ])roducing 

 any progressive movement. The successive stages of tlie first 

 typical reaction to the constant current are shown in Fig. 42. 

 In succeeding experiments on a given individual, and in 

 many cases with the very first experinient, the reaction is 



