CELL LINEAGE IN THE DEVELOPING RETINA OF DROSOPHILA

Analysis of the cell lineage of the Drosophila retina is reported. Mitotic recombination within the white locus results in the formation of small red spots in white eyes; these are found under the dissecting microscope. The spot frequency is low (never more than 1 30 eyes) so that there can be no doubt that each spot is a single clone. Eyes bearing a clone are serially sectioned and all retinula and all pigment cells scored as white or white+. We describe the constitution of 101 clones and examine the disposition of the marked cells in the retinal lattice. The clones are apparently random combinations of the marked cell types-for example, two-celled clones containing one pigment and one retinula cell are frequently found. Our results appear to rule out fixed cell lineage as a determinative mechanism in ommatidial development. © 1979.