Fig. 2. Genetic enhancement of fmi by stbm and stbm by pk. Tangential sections through adult eyes (left) and the corresponding schematics (right). (A) Approximately 12% of ommatidia adopt incorrect polarity in a fmi^frz3/fmi^frz3 hypomorphic mutant. (B) stbm¹⁵³, fmi^frz3/fmi^frz3. Haploinsufficiency of stbm¹⁵³, a hypomorphic allele of stbm, enhances the fmi^frz3 homozygous phenotype 3 fold. (C) About 40% of ommatidia in a stbm¹⁵³/stbm¹⁵³ homozygote display defects in polarity (B. K. Grillo-Hill, unpublished). (D) Flies homozygous for both stbm¹⁵³ and pk^pk1 display an enhanced number of symmetrical defects (yellow) relative to stbm¹⁵³ homozygotes. All sections shown are from the dorsal hemisphere, therefore all trapezoids should be blue. (See Table 2 for quantitative data.) Anterior to the right.