ACTION OF CYTOST 135 



cytost was found to be significantly greater than in the 

 controls. Incidental to these observations, it was noted 

 that the protozoans in the water containing cytost were 

 considerably more active than those in plain tap water. 



In order to examine this further, hanging drops 

 containing a single Paramecium were touched on the 

 periphery with a platinum needle which had pre- 

 viously been immersed in cytost solution. Under such 

 conditions the single animals became very active, dart- 

 ing back and forth across the field. After approxi- 

 mately ten minutes, the magnitude of these movements 

 diminished, shortly assuming a circular path whose 

 radius became progressively smaller until finally the 

 animals simply rotated on their own axis. Controls in 

 drops of tap water did not exhibit such behavior. 



It follows, therefore, that some component of the 

 cytost influences the movement as well as the repro- 

 duction of Paramecium. 



When a loopful of the aqueous cytost extract was 

 added to a few drops of water containing several Para- 

 mecia, 2l similar behavior was noted. Following the 

 onset of the circular movements, the axial rotation en- 

 sued. This became progressively slower, and, after 

 the lapse of an hour and a half, the organisms assumed 

 a spherical form resembling a cyst. It seems likely 

 that this behavior, perhaps the beginning of of en- 

 cystment, represents a response to the unfavorable en- 

 vironment created by too high a concentration of 

 cytost in the aqueous medium. Similar results were 

 obtained when the ash of Paramecia was substituted 

 for the cytost extract, but not when heterologous cy- 

 tost was employed in similar concentration. 



From these experiments, each of which was re- 



