VI.—Ovarian Rhythm in Drosophila

While observations were being carried out on the fecundity of certain experimental Drosophila pseudo-obscura females, it became apparent that there was a regular alternation of periods of rapid laying with periods of no laying. Since an irregularity in rate of oviposition in this species had been noticed by other investigators, and since, under similar circumstances, Drosophila melanogaster lays approximately the same number of eggs each day, it was decided to investigate more closely the possibility that differences in laying habit existed among the various species.