Fig. 1. Morphogenesis of the Drosophila embryonic visual system. (A-D) SEM photos of embryonic head at stage 7 (gastrulation; A), stage 9 (early extended germ band; B); stage 11 (late extended germ band; C) and stage 12 (germ band retraction; D). In all SEM anterior is to the left. Orientation in A is dorsal, whereas B,C and D are lateral views with dorsal up. The migrating eye field (eyf in A,B) and optic placode (opl in C,D) are distinguishable by surface morphology. (E) Fate map of the eye field. Schematic representation of stage 7 embryonic head, lateral view. Approximate position of anlagen are indicated (Bo, larval eye; ed, adult eye disc; ol_a, anterior lip of optic lobe, which gives rise to inner optic anlage; ol_p posterior lip of optic lobe, which gives rise to outer optic anlage). (F) Morphogenesis of the optic placode. Schematic representation of the invaginating optic placode at three successive timepoints. (G) Visual system of late embryo. Other abbreviations: as, amnioserosa; Bn, Bolwig’s nerve; cf, cephalic furrow; fg, foregut; prn, protocerebral neurectoderm.