1. A fragment of the seminal vesicle of Lecithochirium microstomum containing spermatozoa. Scale bar = 2 μm. Spz = spermatozoon, V = seminal vesicle, Vw = seminal vesicle wall.

2–6. Region I of the spermatozoon of Lecithochirium microstomum. Scale bars = 0.2 μm. (2). A longitudinal section of the anterior extremity of the spermatozoon showing the external ornamentation of the plasma membrane. (3). Cross-section in the anterior extremity of the spermatozoon showing the anterior axonemal extremity 1, the external ornamentation of the plasma membrane and some microtubules. (4). Cross-section showing the external ornamentation of the plasma membrane, the anterior axonemal extremity 1 and some singlets of the axoneme 2. (5). Cross-section showing the axoneme 1, the anterior axonemal extremity 2 and the external ornamentation of the plasma membrane. (6). Cross-section with the two axonemes and the external ornamentation of the plasma membrane. Aae1 = anterior extremity of the first axoneme, Aae2 = anterior extremity of the second axoneme, Ase = anterior spermatozoon extremity, Ax1 = first axoneme, Ax2 = second axoneme, B = bulge, Cm = cortical microtubules, Eo = external ornamentation of the plasma membrane, FEo = filamentous ornamentation, S = singlet.

7–12. Cross-sections of Region II of the spermatozoon of Lecithochirium microstomum. Scale bars = 0.2 μm. (7–9). Two axonemes and cortical microtubules. (10). Two axonemes, cortical microtubules and the nucleus. (11). Two axonemes, cortical microtubules, the nucleus and the mitochondrion. (12). One axoneme completely formed, nucleus, mitochondrion, cortical microtubules and the disorganization of the first axoneme. Ax2 = second axoneme, Cm = cortical microtubules, Mt = mitochondrion, N = nucleus, Pae1 = posterior extremity of the first axoneme.

13–14. Cross-section of Region III of the spermatozoon of Lecithochirium microstomum. Scale bar = 0.2 μm. (13). One axoneme, nucleus, mitochondrion and cortical microtubules. (14). One axoneme, nucleus and cortical microtubules. Ax2 = second axoneme, Cm = cortical microtubules, Mt = mitochondrion, N = nucleus.

15–18. Cross-sections of Region IV of the spermatozoon of Lecithochirium microstomum. Scale bars = 0.2 μm. (15). The second axoneme and nucleus. (16). Disorganization of the second axoneme and nucleus. (17). The nucleus surrounded by the doublets of the disorganized axoneme 2. (18). Cross-section in the posterior extremity of the spermatozoon showing only the posterior extremity of the second axoneme. N = nucleus, Pae 2 = posterior extremity of the second axoneme.

19. Transmission electron micrograph of spermatozoa of Lecithochirium microstomum showing glycogen granules (G) revealed by the test of Thiéry. Scale bar = 0.2 μm.