This paper is concerned with morphologic and functional clarification of the human fetal membranes under the electron microscope. The materials were taken from those of early and middle in pregnancy upon eurretage or subtotal hysterectomy, and those of late in pregnancy on cesarean section. and full term normal delivery. These materials, after taken, are immediately fixed in mixed solution of osmic acid and veronal buffer solution and kept in refrigerator for 30 minutes, After rinsing them by water for 30 minutes, dehydration was carried on in ethanol series (50%, 70%, 80%, 90%, 100%) for 30 minutes in each. Sectioning was performed by ultramicrotome and then submitted to electron microscope examination. The results are as follows: 1) Chorionic membrane early in pregnancy shows a significant distinction between the syncitial cell layer and Langhans' cell layer. 2) Syncitial cells have no cellular demarcation each other. 3) Cilia of the syncitial cells project into the intervillous spaces. 4) Intercellular combination of amniotic epithelial cell is not depandant on so-called intercellular bridges, but on stratification of the cytoplasmic project. 5) There is a wavy appearance on the amniotic epithelial cells, beneath which the sawteeth like cytoplamic projects are united with the underlying connective tissues. 6) As pregnancy progresses, the epithelial cell becomes taller followed by its cylindrical modification late in pregnancy. 7) Mitochondria are found rarely in the amniotic epithelial cells, and no secretory vacuoles and granules were seen. Golgi apparatus appears to be not well-preserved. From these findings, it is assumed that there is no secretory activity present in the amniotic epithelial cells. Perhaps, it may thus be denied that amniotic fluid is produced by the amnion.