The stratified epithelium of the seminiferous tubules is composed of different stages of developing sperm cells. Spermatogonia are stem cells located near the basement membrane of the tubule which proliferate by mitosis. Some of the progeny cells differentiate into sperm and move away from the basement membrane toward the lumen of the tubule. These differentiating cells first undergo meiosis, then undergo a morphological change to become spermatozoa. Some of the progeny cells undergo mitosis again to produce more progeny cells providing a continuous source of stem cells for the production of spermatozoa.