THE REACTIONS OF THE FLAGELLATE PERANEMA 95 



acter of the wave is dependent upon the location of the stimulus 

 I am unable to say. At any rate the direction of motion is not 

 changed by reactions of this nature, although the rate may be. 



Thus we see that the reactions of Peranema which regulate 

 the direction of motion are in the nature of trial movements. 

 There is no indication of orientation and procedure directly 

 toward or from objects or solutions, nothing in the nature of 

 a tropism as defined by Loeb. When the animal is stimulated, 

 no matter how or where, it either moves more rapidly or stops, 

 bends toward a given side and takes another course. If this 

 relieves the stimulus it continues, if not it repeats the reaction 

 until the stimulus does not again occur. 



In this connection it is interesting to consider the reactions 

 of specimens entangled in debris. The first response seen after 

 a specimen gets into a fibrous mass which affords some obstruc- 

 tion is an increase in the activity of the flagellum. The tip 

 does not only strike back and forth more vigorously but a 

 larger portion becomes active. If this does not result in freeing 

 the creature it responds by bending the body sharply, i.e., with 

 the bending reaction, and starts in a different direction, after 

 which, if still held fast, it may again lash the flagellum furiously 

 and then again change its direction by bending the body. Thus 

 it continues alternately trying the two different reactions until 

 it becomes free. This indicates that we have here an adaptive 

 change in the character of the response without any change in 

 the environment such as Jennings discovered in Stentor; for it 

 is hardly probable that these different responses can be accounted 

 for by changes in the pressure of the tangle owing to variation in 

 the activity of the flagellum or to the bending of the body. 



Reactions to Chemicals. — My object in studying the responses 

 of Peranema to chemicals was to ascertain if possible whether 

 or not the flagellum is sensitive. In these observations colored 

 substances were introduced under the cover-glass either in 

 solution by means of a fine capillary pipet or as crystals by 

 means of a fine glass rod. The reactions of the animals were 

 then studied as they swam toward the colored substance which 

 gradually spread out in the process of diffusion. 



The responses to chemical stimuli consisted in all cases observed 

 of sharp bending of the body and an abrupt change in the direc- 

 tion of motion just as in the reaction to mechanical stimuli. 



