The ultrastructure of the cortex of Ophryoscolex purkynjei, an entodiniomorphid ciliate obtained from domesticated cattle rumens, was studied and found to have five layers. A particulate and/or filamentous glycocalyx layer, triple membrane layer, homogeneous epiplasmic layer with very fine grains, microtubular layer characterized with a double row of microtubule bundles each containing at most ...