Nosema dollfusi n. sp. (Microsporidia, Nosematidae), a Hyperparasite of Bucephalus cuculus in Crassostrea virginica.*

SYNOPSIS. Sporocysts of the trematode Bucephalus cuculus McCrady in Maryland oysters, Crassostrea virginica (Gmelin), have been sometimes found to harbor a microsporidian parasite considered to be a new species of Nosema. The ovoid spores are about 3 by 2 ü in sectioned material. The spore membrane has a PAS positive mass at the anterior end. The polar filament extends inwardly from this end and coils within a posterior “vacuole.” An anterior “vacuole,” containing no visible structure besides the basal portion of the filament, is also present. The sporoplasm forms a girdle near the middle of the spore. It contains a tiny elongated chromatin mass believed to consist of two nuclei in close proximity.