No. 644] 



THE DURATION OF LIFE 



277 



TABLE I 



It is at once evident, from an examination of the fig^ 

 ures in Table I, and the diagram, that there was no con- 

 siderable difference in duration of life, or in the form 

 of the life curve, for the etherized flies taken as a class,, 

 and the non-etherized groups. It is, however, desirable 

 to examine the results of the experiments in detail in 

 order to see whether there are detectable by biometrie 

 methods any small but still statistically significant dif- 

 ferences between the several groups. To this end, Table 

 II has been prepared, giving the usual biometrie constants 

 for the several series. 



Comparing first the entire etherized group as a wliole 

 with those which never had any ether at all in their lives, 

 it is seen that the mean duration of life (expectation of 

 life at emergence from pupa) is 1.82 4: •'^O days longer 

 in the former (etherized) than in the latter (nomial) 

 group. The difference is thus slightly more than 6 times 



