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 moltinghormones, -ecdysone and ß-ecdysone, in disc developmentis described. A new culture medium has been developed whichallows discs, with either hormone, to undergo all steps of metamorphosis. Time-lapse cinematographic and scanning electron microscopicanalysis of the mechanism of evagination led to the conclusionthat cells probably do not move extensively with respect toone another. In contrast, changes in cell shape appear to playa major role in this process.