ADAPTIVE VARIATIONS. 



379 



stance, Dallinger * has demonstrated a most remarkable 

 and extreme adaptability to high temperature. Start- 

 ing at 15.6 C., he gradually raised the temperature of 

 the water containing these monads up to 70.0 C., when 

 the experiment was ended by an accident. The exact 

 times in the course of the experiment at which a given 

 temperature was reached are not mentioned, but from 

 the description afforded they are gathered to be 

 roughly those given in the accompanying table : 



From this we see that the experiment, as far as it was 

 carried, lasted about six years. The raising of the 

 temperature was not by any means even, the organisms 

 frequently reaching stages at which for months at a 

 time an increase of temperature of half a degree or less 

 was immediately followed by adverse effects, and in 

 some instances by the death of many of the organisms. 

 For instance, when a temperature of 25.6 had been 

 reached, it was found that for a space of five months 

 the temperature could not be raised even .3 of a degree 

 without a distinctly evil effect being produced. In 

 fact, it was found that the progress of acclimatisation 

 at lower temperatures was, as a rule, much slower than 

 at high ones. Thus, within a space of seven months, it 



* Journ. Roy. Microsc. Soc., vol. vii. p. 191, 1887. 



