Fig. 3. Pole cells located in the posterior half of the embryonic gonad directly differentiate into cystoblasts. (A,C) An ovariole with an EGFP-labeled germline cyst in the germarium, as shown in DIC (A) and corresponding EGFP (C) images, from a female that developed from an embryo with a marked pole cell located in the posterior half of the gonad. Note that GSCs (white arrow in C) are not labeled by EGFP. The labeled cystoblasts have by now developed into germline cysts. (B,D) An ovariole with three EGFP-labeled developing egg chambers in DIC (B) and corresponding EGFP (D) images, from a female that developed from an embryo with a marked pole cell located in the posterior half of the gonad. Note that GSCs (white arrow in D) are not labeled by EGFP, thus the labeled egg chambers must have derived from three labeled PGCs that have directly differentiated into cystoblasts. Scale bar in A: 20 µm for A-D.