Fig. 4.

Nuclear ultrastructure of round and elongated spermatids and acrosome formation in Sturnira lilium. (a) Round spermatid without acrosome at stage 5; (b–d) round spermatids with different degrees of nuclear occupation by acrosome; (e–h) elongating spermatids with different degrees of nuclear occupation by acrosome; (i) elongated spermatid with complete formation of acrosome; *, nucleolus; →, acrosomal cap; H, head line of microtubules; ▴, beginning of flagellum formation. Scale bars: (a–d) 2 μm; (e) 1 μm; (f) 2 μm; (g–i) 1μm.