Meria harposporioides is described as a new hyphomycete attacking ciliated protozoans. The crescent-shaped conidium attaches to the host pellicle, invades the cell, and produces branching chains of beadlike assimilative hyphae. A unique feature is that assimilated nutrient is passed back out through the original penetration tube to the infective conidium which then produces fertile hyphae and phialoconidia. This is the first record of a hyphomycete attacking ciliated protozoans.