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Drosophila dorsal–ventral polarity from the oocyte to the first instar larva. The compass at the upper left indicates the direction of Anterior (A), Posterior (P), Dorsal (D), and Ventral (V) for each schematic drawing. Relevant structures are labeled. (a) Stage 10 oocyte. (b) Egg contained within the eggshell. (c) Embryo undergoing germband extension during gastrulation. (d) Cuticle of first instar larva.
