ABSTRACT
The fine structure of the zoospore of Sapromyces androgynus was analyzed to determine if its ultrastructural characteristics could be used to help elucidate the phylogenetic relationships within the Oomycetes. The morphology observed reveals that the zoospore is remarkably similar to the large secondary zoospores of other Oomycetes analyzed. The kinds and positions of the several vacuole and vesicle types, organelles such as K bodies, and flagellar roots, all add further support to the hypothesis that the Oomycetes are a phylogenetically natural grouping. This study allows discussion as to the relationships between Sapromyces and other members of the Oomycetes.