ACCLIMATION IN PLANARIA DOROTOCEPHALA. 



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changes in both directions, are typical of the results of such 

 experiments. Fig. I shows the susceptibility of two lots of 

 worms, the experimental lot (medium-high) from a medium living 

 temperature, represented by the curve a-b; the control (high- 

 high) from a high living temperature, represented by the curve 

 a-c; the susceptibility of both was tested at high. The position of 

 the curve a-b well to the left of the curve a-c indicates that the 

 worms which have been put suddenly from medium into high 

 temperature to test are more susceptible to cyanide than the 

 worms which have been living at that high temperature for a 

 week previous to testing. Fig. 2 shows the same kind of experi- 



rs 



FIG. 2. 



ment with opposite temperature change; here the experimental 

 lot was living at high temperature a week, and its susceptibility, 

 tested at medium temperature, compared with that of a control 

 which had been living at that medium temperature. The curve 

 a-b here represents the experimental (high-medium) lot, the 

 curve a-c the control (medium-medium). The fact that the 

 curve a-b lies well to the right of the curve a-c shows plainly that 

 the worms which have been put into medium temperature to 

 test are less susceptible to cyanide if they have previously been 

 living at high for a week than if they have been in the medium 

 temperature during that length of time. 



