§3] 



TEMPEEATURE-LIMITS OF LIFE 



237 



The determinations given in the above table may be compared 

 only with caution, for diverse conditions give results which 

 cannot be directly correlated. Thus individuals of the same 

 species, but reared under diverse environment, have a different 

 resistance period to heat. The lethal temperature varies accord- 

 ing as the organisms are suddenly or gradually subjected to the 

 high temperature. Also, the individuals of the same species 

 will die at different temperatures according as they are rap- 

 idly subjected to the high temperature or gradually accus- 

 tomed to it, and, as we have seen, a lower temperature, long 

 continued, often produces the same result as a higher tempera- 

 ture during a brief period. Finally, too little care has been 

 exercised in most cases to determine the temperature of the 

 water immediately upon, and a few minutes after, placing the 

 animals in it, — an operation which lowers the temperature 

 of the water. In the experiments cited, unless otherwise 

 stated, the conditions were gradual subjection continued for 

 a short time only. The quality of the water in which the 



