[The surface-coat of Rathke's pouch and the neural tube in embryonic mice]

Mouse embryos, gestation days 10 and 11, were fixed by the method of LUFT (ruthenium red). At the ultrastructural level, luminal epithelial cell membranes of Rathke's pouch and the neural tube were coated with a continuous, electron-dense layer of 100-700 A thickness. The biological property of this surface coat is discussed.