Figure 1

Timing and morphology of meiosis in embryonic chicken gonads, assessed by haematoxylin and eosin staining. Arrows indicate non meiotic germ cells; arrowheads indicate meiotic germ cells. At day 14.5 (stage 40) non-meiotic germ cells are present in the gonads of both sexes, recognised by their large size and pale cytoplasm. Meiotic figures are first seen in some germ cells of left female gonads at day 15.5 (arrowheads). The chromatin becomes condensed and thread-like. By day 18.5, most germ cells are meiotic in the left female gonad. In the right female gonad and in both male gonads, only non-meiotic germ cells are present throughout development. Scale bar = 20 μm.