develops from gastrula embryo stage 6 embryo stage 7 embryo fly_anatomy.ontology DEPRECATION WARNING. 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' carrying 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). FBbt:00005319