HEAT 



113 



by variations in food and presence of a 

 resting stage in the first instar. The third 

 instar runs contrary to expectation; this in- 

 dicates correctly that laws governing heat 

 summation for biological processes are im- 

 perfectly known. 



Experience suggests, however, that 

 summed temperatures are frequently related 

 to the development of many animals and 

 plants in a fairly exact manner. The close- 

 ness of fit is readily disturbed and is par- 



among poikilothermal animals is correlated 

 with Rubner's hypothesis that within a 

 given genetic combination, longevity is 

 inversely proportional to the intensity of 

 living. In other words, this hypothesis 

 states that a definite sum of hving action 

 determines the physiological end of life. 

 Although originally advanced as a result 

 of studies with mammals, this hypothesis 

 is now generally restricted to cold-blooded 

 forms in medial ecological conditions. For 



Table 7. Evidence That, for Many Processes, the Total Amount of Work Done Is Relatively 

 Constant at Medial Temperatures, Regardless of the Velocity Imposed by Temperature 



dcularly faulty when resting stages occur 

 during one of the developmental stages. 

 The relation between summed calories as 

 contrasted with summed temperatures 

 awaits appropriate experimentation. 



RUBNER'S HYPOTHESIS 



The existence of a "developmental total" 

 or "thermal constant" for m.any processes 



example, at medial temperatures, such 

 forms live longer at low temperatures than 

 at higher ones, and various types of 

 measurements indicate that total energy 

 transfomnation is approximately the same 

 regardless of the length of natural life. 

 Some of the supporting evidence for this 

 generalization is given in Table 7. 



Rubner's hypothesis finds general support 



