THE REACTIONS OF THE FLAGELLATE PERANEMA 97 



SUMMARY 



i . Peranema usually moves in contact with the substratum by 

 means of a combination of wave-like contractions of the body 

 and the flagellum, but it can move by the action of either alone. 

 The action of the flagellum is, however, ordinarily much more 

 effective in locomotion than the wave-like contractions. 



2. When very strongly stimulated, as by the addition of 

 chemicals, it swims through the water free from the substratum 

 much like Euglena. This is rarely seen under normal environ- 

 mental conditions. 



3. When crawling the flagellum projects straight forward; 

 only the tip is active, and the organism usually moves on a 

 straight course without rotation on the long axis. When swim- 

 ming the entire flagellum beats in a rotary wave-like fashion, 

 and the body rotates on its long axis and takes a spiral course. 



4. Peranema does not orient. It responds to light very 

 indefinitely if at all. 



5. If the flagellum comes in contact with an object (tactile 

 stimulation) the animal bends always toward the larger lip, then 

 proceeds on a new course more or less nearly at right angles 

 with the old. This same response can be induced by contact 

 stimulation of any part of the body or by chemical stimulation. 



6. There is sometimes local contraction at the point of stimu- 

 lation but this does not appreciably influence the direction of 

 motion. 



7. If the body becomes lodged or entangled in debris while 

 the animal is crawling, the tip of the flagellum gradually beats 

 more and more vigorously and a larger part becomes active. 

 If this does not free the animal it bends toward the larger lip 

 so as to extend the flagellum in a different direction. This 

 then beats again as before, after which the body may bend 

 again. Thus the bending of the body and the activity alter- 

 nate until the animal becomes free or fatigued. This behavior 

 seems to indicate that we have here different methods of response 

 to the same stimulus. 



