Spermatogenesis among several species of Vaucheria has been examined in sections prepared for light and electron microscopy. Early developmental stages of zoosporogenesis and spermatogenesis are identical; however, cytoplasmic cleavage progresses to completion in the antheridium, while incipient cleavage is rudimentary in the zoosporangium. During morphogenesis of the antheridium, nuclear cyclosis is inhibited and flagella develop from nucleusassociated basal bodies. The flagella project into internal membrane reservoirs (termed flagellar pools) which, unlike their counterparts in zoosporogenesis, fail to migrate to the surface of the antheridium, while chloroplasts are excluded from uninucleate protoplasmic segments by completion of cleavage furrow development.