The three-dimensional structure of the vitelline membrane of the hen's egg was observed by optical and scanning electron microscopy. The general structure of this membrane was exhibited even by light microscopy when a mucin-like substance had been removed from the membrane by immersion in lithium carbonate solution.
The vitelline membrane consisted principally of two layers, an inner and an outer layer. The inner layer was a network of flat, solid fibrils 0.2-2.0µ in width. These fibrils were fused with one another in such manner as to form knots. The outer layer was a network of fine, feeble fibrils about 0.07µ in diameter. These fibrils were interlaced with one another in longitudinal and transverse directions and anastomosed a little. There was a chalaziferous layer on the surface of the outer layer. It was composed of bundles or sheets of fibrils. The chalaza was revealed as a condensed amorphous mass of gel-like substances.