Fig. 12-19.

Germ cell development progresses from the basal lamina towards the lumen of the tubule. Each germ cell type forms a different layer in the seminiferous rubules and may be identified by its nuclei. Spermatogonia are basal cells with pale cytoplasm, round nuclei, and eccentric nucleoli. Above these cells, the Sertoli cell nuclei may be recognized by their large central nucleoli. The inner layers consist of primary spermatocytes showing the chromatin pattern characteristic of meiosis. (Semi-thin section.)