Diagram of Embryonic Stages

Stages in embryonic development of Drosophila melanogaster

 

(A) Early cleavage (15 minutes–1.5 hours). Nuclei cleave in the central region.

(B) Migration of cleavage nuclei (1.5 hours). Nuclei migrate to the periphery.

(C) Formation of syncytial blastoderm (2 hours). Pole cells form posteriorly.

(D) Cellular blastoderm (2.5 hours). Cell membranes form between the nuclei.

(E) Early gastrulation (3.5 hours). The ventral furrow forms. Thickening of the posterior plate below the pole cells.

(F) Midgut invagination (3.5–4 hours). The midgut invagination can be seen ventrally, as can the cephalic furrow.

(G) Germ band extension (4–5 hours). Invagination of the hindgut can be seen dorsally.

(H) Stomodeal invagination (5–7 hours). Invagination of the stomodeum can be seen ventrally.

(I) Shortening of the germ band (9–10 hours). Foregut and hindgut invaginations are deep.

(J) Shortened embryo (10–11 hours). Hindgut is now fully posterior.

(K) Dorsal closure (13–15 hours). The ectoderm closes dorsally. The midgut broadens. The head involutes.

(L) Condensation of ventral nervous system (15 hours–hatching). The gut regions are joined. The nervous system forms ventrally.