Pasteuria ramosa, a bacterial parasite of the cladocerans Daphnia pulex and D. magna, was described by Metchnikoff in 1888. Because the organism could not be cultured, it was subsequently lost. However, the original illustrations and descriptions of the life cycle of P. ramosa are similar to a bacterial spore parasite of nematodes (BSPN) that was recently described in Meloidogyne. As a result of these similarities, a search for P. ramosa was initiated. An organism resembling P. ramosa was found infecting Moina rectirostris, a member of the Daphnidae and a new host for the bacterium. Photomicrographs and scanning electron micrographs of the parasite indicated that the morphology of this organism was similar to the descriptions and illustrations presented by Metchnikoff. Morphological features of this newly described parasite also indicated that the bacterium is similar to the BSPN.