Fig. 1. A sensitized genetic screen for dosage-sensitive enhancers of lz^ts1. Scanning electron micrographs of adult eyes. Posterior is to the left and dorsal is up. All flies were reared at 25°C except for the one shown in C which was reared at 29°C. (A) The wild-type Drosophila eye has a regular array of ordered facets. (B) lz^ts1 flies, when reared at 25°C, have wild-type eyes. (C) When lz^ts1 flies are reared at 29°C, the eye appears rough and disorganized. (D) lz^R1, which is a null allele of lz, gives rise to a more severe eye phenotype than lz^ts1 at any temperature. (E-I) Interacting mutations. When raised at 25°C, in a lz^ts1 background, loss of one copy of each enhancer locus causes a slight roughening of the posterior area of the adult eye. Under a light microscope the eyes also appear to be slightly glossy, suggesting a defect in lens secretion. (E) lz^ts1; en(lz)3C/+. (F) lz^ts1; en(lz)Y/+. (G) lz^ts1; en(lz)D/+. (H) lz^ts1; en(lz)4G/+. (I) lz^ts1; en(lz)4F/+.