INTERFERENCE OF EXCITATIONS 



195 



form the elements which bring about a screw-like movement on 

 the axis. They further possess several cilia, which permit a re- 

 bounding of the organism, and finally certain forms have anal- 

 cilia, which probably serve as breaks and to steer the organism. 

 (Figure 43.) Their usual mode of locomotion is that of creep- 

 ing, moving by means of the cilia on the ventral surface. These 

 movements depend upon the positive thigmotaxis of the cilia of 

 locomotion. At the same time there is inhibition of the cilia on 



Fig. 43. 

 Hypotrichous infusoria. A Stylonychia. B Urostyla. 



the sides. When the infusoria are excitated by a new stimulus, 

 the cilia used for rebounding become active, the body frees itself 

 from its position of attachment and begins to swim, wherein the 

 cilia on the sides, as well as the perioral cilia, act in the manner 

 mentioned above. I have made the striking observation that the 

 hypotrichous infusoria respond differently to the galvanic cur- 

 rent, depending on whether they are swimming or in a fixed 

 position. If one places a drop of water with numerous Urostyla 

 on a slide between parallel pieces of fired clay which serve as 

 electrodes, it will be seen, upon the closing of a current, that all 



