UPPER THERMAL DEATH POINTS 441 



exposure to the particular fatal temperature under considera- 

 tion, but in addition, an exact statement of the manner in which 

 this temperature was reached. 



SUMMARY 



1. The length of life of starfish larvae eighteen to forty-eight 

 hours old at temperatures between 32° and 40°C. is governed 

 with a very fair degree of accuracy by the relation: 



— — = Qi = approximately 2. 



For Paramecium, the value of Qi is subject to considerably more 

 variation; above 40°C. it is frequently in the vicinity of 3; 

 below 40° often less than 2. 



2. Knowing the above relation and the length of life after a 

 sudden exposure to one or more selected temperatures, it is 

 possible to calculate by the method given in the body of the 

 paper the point at which death ought theoretically to occur 

 when the temperature is raised uniformly at any given rate. By 

 comparing this point with the observed death point under the 

 same conditions, it can usually be determined whether or not 

 acclimatization has occurred. 



3. With the different rates of temperature increase employed 

 in these experiments the observed death points of starfish larvae 

 agree very closely with the calculated ones, indicating prac- 

 tically no acclimatization. With Paramecium caudatum the 

 observed death point may be much higher than the calculated 

 one, indicating that acclimatization occurs even in experiments 

 of short duration. 



4. If desired, the 'surplus resistance' in a given experiment 

 may be obtained in quantitative form by determining the excess 

 in area enclosed by the curve of injury up to the point of death, 

 over the area (taken as unity) which represents an amount of 

 injury just fatal when the temperature is changed suddenly. 



5. As determined in this way, the 'surplus resistance' for star- 

 fish larvae for a number of different rates of increase of tempera- 



