Early spermiogenesis in Chimaericola leptogaster. A, early zone of differentiation. Intercentriolar body next to cell membrane. B, C, fully developed zone of differentiation, longitudinal sections. Intercentriolar body flanked by two centrioles, each associated with a striated root. Two free flagella and one median cytoplasmic process are attached at the distal extremity of the zone of differentiation. D, E, longitudinal sections of late zones of differentiation, embedded in the cytoplasm of the mass of spermatids. Arching membranes at the proximal extremity of each zone of differentiation. Scale in all figures: 1 μm.