Abstract
The number of pupæ formed per female, the duration of the larval period, and the duration of the pupal-imago period of a normal Drosophila culture and of the 230th generation of an aseptic culture which had been kept in the dark have been determined. The larval period and the pupal-imago period were found to be nearly the same for both cultures under both favorable and unfavorable conditions. There is no evidence, therefore, to show that inbreeding, absence of light, or growth in the absence of bacteria for 230 generations has had any effect either on the duration of life or on the ability of the organism to resist unfavorable bacteria.