ACCLIMATION IN PLANARIA DOROTOCEPHALA. 



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excess weight was put on alternate sides in duplicate experiments, 

 and the position of experimental and control worms in the 

 apparatus was alternated. It should be stated, of course, that 

 only those temperature combinations could be employed in 

 which the testing and the control temperatures were medium 

 since that was the only temperature at which the biometer could 

 be operated. The "low-medium" group gave the same results 

 as the colorimetric experiments of Table IV. above, as far as 

 tried out. But it is from the "high-medium " lot, the one furnish- 

 ing the less complete records in the colorimetric estimations, that 

 the data below are quoted, since they are characteristic both as 

 regards the majority results and the exceptions. Table V. is a 

 summary of the results of these experiments. Worms which 

 had been living at high temperature were put into the biometer 

 at medium and their CO 2 production as determined by BaCO 3 

 precipitation was compared at that temperature with that of 

 worms which had been living at the medium temperature 



indefinitely. 



TABLE V. 



The results in the majority of the experiments harmonize 

 with what we should expect from previous experiments. Of the 

 13 experiments here, 8, that is, nearly 62 per cent., show that 

 animals which have been living at a higher temperature produce 

 CO 2 less rapidly, that is, they have a lower metabolic rate when 

 tested out at a lower temperature than do animals which have 



