Overview of vegetative cells and colonies. Emergence of spermatogonia, primary and secondary meiotic nuclear divisions in the spermatocytes, release of spermatozooids. Development of oogonia, primary and secondary meiotic nuclear divisions (pycnotic nuclei). Penetration of sperms into the oogonium, their migration to the egg nucleus, formation of auxospores with first and second shells, germination of initial cell. With time-lapse.