substage of immediately preceded by developmental stage gastrula stage embryonic stage 6 embryonic stage 7 FBdv:00005319 Temporal ordering number - 240. FlyBase_development_CV Stage 7 begins when the pole cells have adopted a dorsal (horizontal) position at the posterior. Invagination of the anterior and posterior midgut and hindgut follows. The 'discoid plate' that carries the pole cells forms a pocket. Transverse furrows (dorsal folds) form on the dorsal surface. This stage ends when the anterior wall of the amnioproctodeal invagination starts moving anteriorly and the pole cells are no longer visible externally. Duration at 25 degrees C: approximately 10 minutes (180-190 minutes after egg laying).