Spermatogenesis, light micrograph. The seminiferous epithelium of the testis serves the purpose of producing sperm via the process of spermatogenesis. From the respective outer, or basal, region towards the apex of the epithelium, immature germ cells divide and develop into more mature germ cells. Elongating spermatids are easily identified as pale elliptical nuclei with a dense acrosome forming the cranial or leading aspect. This particular shape is characteristic of guinea pig sperm at stage X of the spermatogenic cycle. Epoxy resin section, Toluidine blue stain. Magnification: x 400 when width printed at 10cm.