The various types of human primary spermatocytes were classified by means of morphological and morphometrical studies. Based on this classification, the topographic arrangement of the spermatocyte populations in the longitudinal course of seminiferous tubules was determined. This analysis revealed human spermatogenesis be to subjected to a complex local plan of organization, which is based upon the geometry of spirals. The centers of gravity of spermatocyte populations of subsequent degrees of differentiation are arranged on helices that are contracted conically to the lumen of the seminiferous tubule. On these helices the centers of gravity of the populations diverge continuously 173.8 degrees +/- 32.4 degrees. Populations of the same degrees of development are arranged on helices with constant diameters. On these helices the centers of gravity of the populations diverge continuously 142.6 degrees +/- 14.2 degrees. The present results lead to new aspects of the kinetics and morphogenesis of the seminiferous epithelium, which can be integrated into a comprehensive biological concept.
