6l6 Lorande Loss Woodruff. 



was identical except that the duration of the stimulation was ten 

 minutes instead of thirty minutes. 



The immediate effect of immersion in the monobasic salt was 

 to cause the infusorian to rotate rapidly on its short axis for a 

 couple of minutes, after which it began to move slowly about the 

 slide, and by the end of the thirty minutes normal locomotion was 

 entirely resumed. Practically the same behavior was caused by 

 the application of the dibasic salt. I found, however, that this 

 typical reaction varied somewhat with different individuals at 

 various times; sometimes, for instance, the duration of the whirl- 

 ing motion was very much shorter and sometimes it was entirely 

 absent. This is true not only for stimulation with potassium 

 phosphates but also for stimulation with the various other salts 

 tried. Slightly different reactions occurred with some of these 

 other salts, but I have noticed the same variability. I am inclined 

 to believe that ihe explanation of this variability in the reaction to 

 a given stimulus at different times is in some way correlated with 

 the slight changes in vitality which I have described as rhythms. 

 I found also that when the salts were applied daily they soon 

 ceased to cause any abnormal movements, even when their effect 

 on the vitality of the animals, as determined by the division-rate, 

 was detrimental. Here again there were occasional exceptions 

 which point to periodical fluctuations in sensitiveness. This holds 

 true for all the salts employed. 



A glance at the diagram shows that the culture stimulated ini- 

 tially with K2HPO4 in yyVo solution divided more rapidly than the 

 control during three out of the four five-day periods of the experi- 

 ment, and produced a greater effect than any of the three other 

 experiments involving initial stimulation. Culture K2HPO4 y"^, 

 initial stimulation, showed the next greatest effect, but this was 

 manifested in a slowing of the rate in three out of four periods. In 

 initial doses, then, the dibasic salt proved to be more effective — the 

 greater dilution producing an accelerating effect and the lesser 

 dilution producing a retarding effect. An examination of the 

 data of the experiments on daily stimulation shows that K2HPO4 

 i ' 2" again produced the greatest change in rate, though this time 

 it had a retarding influence.^ Summarizing the results of the 



'The curve for daily stimulation is not plotted for KH2PO4 -^5,^ and -j-r-^j^* during three periods 

 because the individuals stimulated were lost accidentally at these times. 



