STUDIES ON THE DURATION OF LIFE 209 



of the sea urchin and could only be carried out at the upper temperature 

 limits of the organism, since at ordinary temperatures this organism lives 

 for years. In the upper temperature region the temperature coefficient 

 for the duration of life was very high, probably on account of the fact 

 that, at this upper zone of temperature, death is determined by a change 

 of the nature of a coagulation or some other destructive process. Moore, 

 at the suggestion of Loeb, investigated the temperature coefficient for the 

 duration of life for the hydranth of a tubularian at the upper temperature 

 limit and found that it was of the same order of magnitude as that 

 previously found for the sea urchin egg. In order to prove that there 

 is a temi>erature coefficient for the duration of life throughout the whole 

 scale of temperatures at which an organism can live, experiments were 

 required on a form whose duration of life was short enough to measure 

 the duration of life even at the lowest temperature. 



A suitable organism was found in Drosophila. This 

 was grown under aseptic conditions, as already described. 

 The general results are shown in Table 25. 



TABLE 25 



Effect of temperature on duration of life of Drosophila. 

 (After Loeb and Northrop) 



From this table it is seen that at the lowest tempera- 

 ture the duration of life is longest, and at the highest tem- 

 perature shortest. Cold slows up the rate of living for 

 the fly. Heat hastens it. One gathers, from the account 

 which Loeb and Northrop give of the work, that at low 

 temperature the flies are sluggish and inactive in all 



14 



