[Electron microscopic study of the development of the seminiferous tubule from birth to the end of the 1st year].

The development of the seminiferous tubule in the first year of life was studied with the electron microscope in five biopsies of normal testes. When HCG stimulation ceases, the fetal Sertoli cell changes into the Sa-Sertoli cell. The possibility of the fetal Sertoli cell having a hormone producing role is discussed. Gonocytes can be detected until the third month post natum. In addition to the gonocytes fetal, transitional, Ap and Ad spermatogonia are also present in the first year of life.