females produce few if any eggs. Most egg chambers of homozygous females degenerate after King stage 6; a few cysts escape to produce stage 14 oocytes which are retained in the ovariole. Vitellogenesis severely inhibited and uptake of protein from the hemolymph apparently impaired. (Mulligan and Rasch, 1980). Nucleoli of nurse cells morphologically aberrant (Mulligan and King, 1976). Oocytes grow at reduced rate and become covered by multiple layers of follicle cells, which secrete abnormal egg coverings (Mulligan and King, 1976). Phenotype insensitive to ecdysone administration and pole-cell-transplantation (Lamnissou and Galti-Douka, 1986; Mulligan and Rasch, 1980). Mosaic studies by Wieschaus, Audit and Masson (1981) indicate that the gene functions in the germ line, presumably in the nurse cells.