292 ELLINOR HELENE BEHRE. 



bility begins. The table shows the difference in susceptibility 

 between the two lots. Thus no. I, for example, shows that the 

 susceptibility of a lot ("control") brought from low to high 

 temperature only when the susceptibility determination is begun 

 is greater than that of a lot ("experimental") which has been 12 

 hours at the high temperature before the susceptibility determina- 

 tion. 



We can see from a glance at Table III. that there is much 

 greater variability in the results in the raised temperature series 

 than in the series with lowered temperature. Predicting results 

 on the basis of the previous set of experiments, we would assume 

 that after 12 hours in a higher temperature than the living one, 

 before subjection to the KNC, the worms would be somewhat 

 less susceptible than similar worms subjected to the new tem- 

 perature and cyanide simultaneously. In other words, they 

 should have become acclimated to some extent to this second 

 change. Of the 23 series tested to determine this point ten 

 gave the predicted result, six the opposite and seven showed no 

 difference between the experimental and the control animals. 

 Let us examine these to see whether a reasonable explanation for 

 these very variable results can be found. One fact which may 

 throw light on this question is the following: From examination 

 of the graphs, which are not given here for lack of space, it is 

 very evideat that of the ten series which gave the result which 

 we predicted from the findings in Table II., one showed a time 

 interval of five hours between the death of the two series, one 

 four hours' difference in time, and four two hours or very little 

 less. The time intervals between complete disintegration of the 

 two lots which showed the opposite type of result (those in which 

 12 hours' acclimation did not decrease susceptibility) were mostly 

 shorter; the curves were closer together as a rule. Apparently, 

 then, acclimation to raised temperatures is less rapid than 

 acclimation to lowered ones since susceptibility seems to be 

 much less altered by 12 hours at a temperature higher than that 

 at which the worms have been living than it is by 12 hours at a 

 temperature lower than that at which they have been living. 

 In the case of the highest temperature used, this apparent 

 retardation in the process of acclimation may perhaps be ex- 



