This title presents a critical comparative review of the morphology and ultrastructure, morphogenesis, cytology, molecular biology and evolution of the biflagellate fungi. These organisms encompass the fungi formerly called oomycetes, taxonomically related heterotrophs studied by mycologists, plasmodiophorids and other heterotrophs. Appropriate comparisons are made with chromophyte algae, marine heterotrophs and chytridiaceous fungi. Little-known taxa which have been referred to the various orders of flagellate fungi are also listed together with citations. A new hierarchical classification...