Fig. 3. Co-culture of dissociated testicular cells on ZtA6 feeder cells. Male germ cells were attached on the feeder cells as a clump. (A-L) The same single clump was observed every day from 3 days to 14 days of culture. (M) On day 15, the clump had disappeared; however, an aggregation of flagellated sperm was found in suspension. (N) Control normal mature sperm. As the germ cells divided, the clump became larger (A-F) until the appearance of flagellated sperm on day 9 (G). It then decreased in size (H-L). The nuclear sizes of flagellated sperm (arrowhead) on days 9 (G), 12 (J) and 13 (K) are similar to those of normal mature sperm (N). Scale bar: 10 µm.