Spermiogenesis (sperm maturation), Golgi phase

In the Golgi phase of spermiogenesis multiple Golgi complexes (G) accumulate. Proacrosomal granules (Gr) of these coalesce to form the acrosomal vesicle (Ac). This then spreads over the anterior half of the nucleus (N), forming the acrosomal cap. Mitochondria (M), microtubules (Mt), endoplasmic reticulum (ER).(testis mouse)
Porter, KR and Bonneville, MA, Fine Structure of Cells and Tissues, 4th ed., Lea & Febiger, Philadelphia, 1973, p.100.

Spermiogenesis, spermatids

Portions of two spermatids (guinea pig) showing the intercellular bridges by which they are joined to each other and to two other spermatids of the same cluster. The small arrows indicate the local thickening of the cell membrane encircling the bridges. The large arrows passing through the bridges indicate the sites of continuity of the cytoplasm from cell to cell. Acrosome is forming adjacent to nucleus.
Bloom, W and Fawcett, DW, A Textbook of Histology 10th ed., WB Saunders, Philadelphia, 1975, p. 823.

Spermiogenesis, spermatid (almost mature)

Nearly mature sperm with head (hook-shaped in this case, mouse) contains the nucleus (N), topped by the acrosome (Ac). Two centrioles are involved in the formation of the neck region. One of these (Ce) initiates the development of the long bundle of filaments (C ) that is the core of the middle piece and tail. The core has an internal structure similar to an cilium. The middle piece of the flagellum is wrapped by a sheath of mitochondria (M). The tail proper is a fibrous sheath (FS) wound around the axial filamenture. The asterisk indicates a cellular bridge between spermatids. Mitochondria (M), endoplasmic reticulum (ER).
Porter, KR and Bonneville, MA, Fine Structure of Cells and Tissues, 4th ed., Lea & Febiger, Philadelphia, 1973, p.96.