Reactions of jEolosoma to Chemical Stimuli 6l 



like that shown in Fig. 2A, the first contraction throws the head 

 nearer to the stimulus. This is followed by a reverse movement 

 in which the animal moves away. If as in Fig. 2B, the first con- 

 traction turns the animal away from the stimulus and movement is 

 continued in that direction. This principle holds true regardless 

 of the direction from which the pipette may throw the impinging 

 chemical upon the body w^all, — whether it be directed toward 

 either side, dorsally or ventrally. The "secondary reflexes'' — • 

 those movements which immediately follow, this first reflex — are 

 such as to move the animal away from the field of stimulation. 



Organic Acids and Hydrates. Reactions to these solutions were 

 similar to those developed by the mineral acids. With the hydrates, 

 however, it was noticed that many individuals would stop in 

 their onward rush from the stimulus, would curl up in crescent 

 shape, and seemingly rub tne prostomium to and fro with a lateral 

 swing on the substratum. When placed in a culture jar after the 

 experiment they invariably burrowed into the ooze at the bottom 

 of the jar. 



Carbonates. There are quick negative reactions to the car- 

 bonates at both head and caudal segments, though the animal 

 makes but little eflFort to get away from the stimulus. When 

 stimulated at the side so that the ventral contraction throws the 

 head nearer to the pipette, in few cases was there any evidence of a 

 reverse movement. Vigorous puckerings of the prostomium were 

 noticeable; a few writhing movements were made; and then the 

 animal would usually lie dormant until the effect of the stimulus 

 passed away. 



Halides. The initial reaction to the halides was like that to the 

 acids. These were invariably followed by so marked an increase 

 in the peristaltic waves, however, that progressive movements 

 were inhibited for some time. The K solutions stimulated 

 increased peristalsis much more vigorously and quickly than the 

 Na solutions. 



Sulphates. When FeSO^ is introduced directly in front of the 

 animal, the head is slowly waved to and fro, laterally, several 

 times, after which the vEolosoma curls up with a twisting motion, 

 and makes no effort to move away. When introduced laterally the 



