494 Physiology 



the species. Amoeba proteus shows a well defined orientation in direct 

 current and moves toward the cathode, whereas A. dofieini shows no re- 

 sponse (385). The reaction of A. proteus (168, 385) depends upon an 

 induced solation at the cathodal surface, resulting in a decreased elastic 

 strength of the plasmagel in this area. The response of the organism de- 

 pends upon its orientation when stimulated. Amoebae moving toward 

 the anode show reversal of protoplasmic flow at the cathodal end, fol- 

 lowed by cessation of flow at the anodal end. If the current is too strong 

 and the medium is not acid, disintegration of the organism begins at the 

 anodal surface, whether the amoeba is moving toward or away from the 

 cathode. With weaker currents, the direction of locomotion is reversed. 

 Cilia tes (249, 388) usually react to a direct current by reversal of the 

 ciliary stroke on the cathodal surface. As a result, the body is turned so 

 that the organism swims toward the cathode. In a strong but sub-lethal 

 current, ciliary reversal may be so extensive that the ciliate swims back- 

 ward toward the anode. 



Responses to temperature 



Reactions to unfavorable temperatures, as described for various 

 ciliates, involve typical motor responses similar to those noted under 

 stimulation of light in certain species. The response is repeated until the 

 path of locomotion takes the organism into a region with a more favor- 

 able temperature. 



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