Spermatozoon of Pleurogenoides medians, posterior or nuclear part (Region III); all cross-sections except (f). (a, b) End of the two bundles of cortical microtubules (CM); G, granules of glycogen; M2, second mitochondrion; N, nucleus. (c) Disorganization of the first axoneme resulting into the central core (CC), doublets (D) and singlets (S). G, granules of glycogen; M2, second mitochondrion; N, nucleus. (d, e) Disappearance of the second mitochondrion (M2). G, granules of glycogen; N, nucleus. (f) Posterior spermatozoon extremity (PSE). Note the posterior nuclear extremity (PNE). Cross-sections of levels * and ** are shown in (g) and (h). Ax, axoneme; G, granules of glycogen; N, nucleus. (g, h) Sections similar to level of * and **, respectively, in (f). G, granules of glycogen; N, nucleus. Scales in μm: 0.3.