3OO ELLINOR HELENE BEHRE. 



been living at that lower temperature. Of the other four experi- 

 ments, one, no. 8 (with positive results) has been left out of 

 account, as it seemed probable that there was a leak in the 

 biometer. In considering the exceptions we must bear in mind 

 that small differences in weight may be enough, when dealing 

 with such small amounts of protoplasm, to account for variations. 

 Among the exceptions, three, nos. 4, 7 and 13, have the excess 

 weight on the experimental side, but this is not the case with the 

 fourth, no. 12; so weight can hardly be considered the explana- 

 tion. As earlier experiments had shown that it was hard to 

 maintain high temperature stock at the usual size on tri-weekly 

 feedings, it seemed worth while when the first few cases of non- 

 conformity appeared, to consider whether the irregularity could 

 be found to have a definite relation to the nutritive conditions. 

 But after daily feeding of one stock for a month, the last three 

 experiments, 11,12 and 13, failed to support any such theory. The 

 excess weight was always on the experimental side yet the results 

 differed in the different experiments, with no direct relation to 

 the feeding. The exceptions here are probably due to slight 

 differences in motor activity and to individual variations. As 

 has been said above, since single individuals are used the effect 

 of such-differences must be relatively great. 



From data on carbon dioxide production, then, we may draw 

 conclusions identical with those to which the data from suscepti- 

 bility experiments lead us. Worms which have been living at a 

 given temperature for even as short periods as 12 hours have 

 undergone an alteration in metabolism shown in this case by an 

 alteration in CO% production. This alteration results in the 

 production of more CO^ by worms whose living temperature was 

 lower than the testing temperature than by worms whose living 

 and testing temperatures were the same (higher) ; and less COo 

 production by worms whose living temperature was higher than 

 that at which they were tested than by worms whose living and 

 testing temperatures were the same (lower) temperature. 



VI. INFLUENCE OF TEMPERATURE ON HEAD-FREQUENCY. 



A. Direct Effect of Altered Temperature. 



I. During the Entire Period of Regulation. Before taking up 

 the question of the effect of acclimation to certain temperatures 



