The ciliated ependyma of the hypothalamus of the hanster (Cricetus cricetus) consists of a sheet of cells, the luminal surface of which is reflected over cilia and numerous microvilli. The lateral portions of the plasmalemma of contiguous cells are fused at some sites to from junctions of five layers, the zonula occludens. These fusions occur usually in continuity with other intercellular junctions, the zonula adhaerens. In the apical regions of the ependyma these fusions are almost spiralled. The nucleus is regularly oval and lying close to the basal plasmalemma. The cytoplasm contains a finely granular matrix, filamentous components close to the junctions. The endoplasmic reticulum is sparse. The Golgicomplex is confined to the supranuclear cytoplasm, and mitochondria, are more numerous in the apical than in the basal regions of ependymal cells; the mitochondria are generally rounded and have transverse cristae and granules. The apical regions of the cytoplasm contain the basal bodies of cilia; they form non-striated rootlets and the rootlet filaments tend to diverge, ending in a granular zone.