SYNOPSIS.
An accurate description of Cyclidium glaucoma O.F.M., 1786, is presented. Fixed specimens were treated with the Chatton‐Lwoff silver impregnation technique and the standard Feulgen nucleal reaction. Living material was examined by phase microscopy. Components of the infraciliature have been given special attention, particularly in the buccal area. In brief consideration of the systematic status of this species emphasis is placed upon the close relationship of the pleuronematine and tetrahymenine groups of hymenostome ciliates. Comparisons on structures found in C. glaucoma with corresponding structures in species belonging to quite closely related families are made, and the fundamental nature of the infraciliary tetrahymenal buccal apparatus and the polar basal granule‐complex is discussed.