Abstract
Flies of (1) stocks homozygous for the normal alleles of [gamma] and sn 3 and also homozygous for c3G , and (2) stocks homozygous for [gamma] sn 3 and also for c3G were crossed reciprocally and the F 1 [female] [female] ([gamma] sn 3/+ + ; c3G/c3G) were examined for mosaic spots. Not less than 22% of the flies showed somatic spots due to mitotic crossing-over. Elimination of meiotic crossing-over because of the presence of c3G did not prevent this effect in the somatic cells of Drosophila [female] [female] .