THE PROBLEM OF ACTIVATION 



249 



quent development (see the first table above). (3) In 

 e"ach experiment the percentage of reacting eggs in- 

 creases with time of exposure to an optimum and then 

 decreases. (4) The optimum time for production of 

 larvae at 31 is 14 to 15 minutes; at 32, from 6 to 8 

 minutes; that is, the rate of the activation reaction is 

 approximately doubled by a rise of i in temperature. 

 At 33 the optimum exposure is about 4^ to 5! minutes; 

 at 34, 3 to 4 minutes; at 35, ij to .2 minutes; and at 

 36, i to ij minutes. 



The range of effective temperatures is from about 

 29 to 38. The following table shows the time varia- 

 tions for various effects within this range: 



APPROXIMATE TIMES OF EXPOSURE REQUIRED TO PRO- 

 DUCE THE FOLLOWING EFFECTS AT DIFFERENT 



TEMPERATURES 



Commenting upon the process underlying the time 

 variation at the different temperatures, R. S. Lillie says: 



In endeavoring to form some consistent conception of the 

 nature of this process, the following facts have to be consid- 

 ered. It exhibits a high temperature coefficient: from fifteen 

 to twenty times the duration of exposure is required to induce 



