Maintenance of determination by cells of imaginal discs ofDrosophila after dissociation and culture in vivo.

Wild type cells of imaginal wing discs or embryos were dissociated and mixed in different proportions with cells of genetically marked wing and/or leg discs. These latter were X-irradiated to such an extent that their rate of proliferation was drastically lowered. They served as a "feeding layer" in which the interspersed wild type cells could be cultured. The reaggregates were allowed to grow in vivo, and fragments of them were tested for recovery of imaginal structures formed by wild-type cells.The experimental conditions for maximal dilution and maximal recovery of wildtype cells were first analysed. Under these conditions the progeny of cells deriving from different fragments of mature wing discs are capable of forming large territories of cuticle. These consisted preferentially of structures located in the region from which their ancestral cells were derived. The proliferating cells remained confined to either the anterior or the posterior wing compartments, but were apparently able to transgress the dorsalventral compartment border. Cells with qualities for distinct imaginal discs and possibly regions could also be recovered from dissociated embryos of 7 h age. The efficiency with which imaginal structures could be recovered as well at the types or qualities of these structures did not depend on the histotype of the feeding layer.