In Vitro Development of Drosophila Imaginal Discs: Hormonal Control and Mechanism of Evagination

A new approach in the understanding of the role of the two molting hormones, α-ecdysone and β-ecdysone, in disc development is described. A new culture medium has been developed which allows discs, with either hormone, to undergo all steps of metamorphosis. Time-lapse cinematographic and scanning electron microscopic analysis of the mechanism of evagination led to the conclusion that cells probably do not move extensively with respect to one another. In contrast, changes in cell shape appear to play a major role in this process.