No. 646] 



THE DURATION OF LIFE 



403 



human longevity are such things as the infectious dis- 

 eases, exposure to unfavorable environment, etc. But 

 Drosophila, which so far as is known has no infectious 

 diseases, and in general meets a set of environmental 



AGE CENTILES 



conditions wholly different, both qualitatively and quan- 

 titatively, from those which operate on man, shows 

 fundamentally the same form of distribution of degrees 

 of longevity. 



