Carp erythrocytes have been observed with a light microscope as well as an electron microscope in ultrathin sections revealing the following results: 1. The dense body, which appears in the cytoplasm, is connected with the cell membrane and nuclear membrane through a fine tube. 2. The nuclear membrane is composed of a porous external layer and a compact internal layer. 3. The chromatin granules 0.2-0.4μ in diameter and coiled threads are revealed in the nucleus. The former is stainable, but the latter has never been stained with Heidenhain's iron hematoxylin.