dense, sometimes crystalline core (Desser and Lester, 1975, loc. cit.). This core has been shown recently to be composed partially of RNA (Barber et al., 1979, loc. cit.) which has not been demonstrated in rhoptries. Finally, the typical apicomplexan pellicular complex is not seen in the rodlet cells which are bound by a thickened wall containing many closely spaced, actinlike microfilaments that form a girdle around the circumference of the cell. In conclusion, none of the key apicomplexan features is found in rodlet cells. Moreover, in the many studies of these cells, the characteristic apicomplexan asexual stages (schizogony and/or sporogony) have never been observed. Until more is known about these peculiar cells, we suggest that they be referred to as "rodlet cells." If they are indeed parasites, they are unlike any known parasitic protozoan. We are grateful to the Ontario Ministry of Natural Resources for the use of their facilities at the Wildlife Research Station, Algonquin Park, Ontario, and to the Natural Sciences and Engineering Council of Canada for financial support (Grant #6956).