[The effect of Colchicine on the differentiation and the frequency of transdetermination in leg imaginal disks ofDrosophila melanogaster].

1. Treatment of male foreleg disks of late 3rd instar larvae ofDrosophila melanogaster with Colchicinein vitro (Conc. 0.005-1 mg/ml) and implantation into larval hosts of the same age results in the formation of a characteristic pattern of damage, whereby the trochanter is most severely reduced. Claws are much more sensitive to the same concentration of the drug than the sex comb teeth. 2. When Colchicine-treated disks are implanted into young larval or adult hosts, the disks proliferate and structures of all leg segments can be formed. The frequency of the different leg structures formed depends on the concentration of Colchicine used and on the length of the culture period. 3. After culturing the Colchicine-treated disks for 8 days in adult hosts, transdeterminations occur in many disks. The pattern and relative frequencies of allotypic structures formed are identical after Colchicine treatment and mechanical disintegration of the disks. 4. Bristles without sockets or any other modification of the bristle organ were never observed, even after treatment of the disk with high concentrations of Colchicine.