Abstract
Dangeardia ovata. parasitic on Sphaerocystis schroeteri Chod., a new species of chytridiaceous fungi, is described from a lake in Washtenaw County, Michigan. The parasitism by Rhizophydium megarrhizum Sparrow on Lyngbya sp. and Aphanizomenon flos-aquae (L.) Ralfs is discussed. Several incompletely known chytrids and 2 saprolegniaceous fungi parasitic on phytoplankters are presented. In addition, 1 chytridiaceous and 2 saprolegniaceous parasites found on zooplankters are discussed.