- the primitive layer of cells that results from the segmentation of the ovum.
- the layer of cells forming the wall of the blastula, and in most vertebrates enclosing a cavity or a yolk mass.
- the layer of cells that surrounds the blastocoel of a blastula
- a flat disc of cells formed after cleavage in a heavily yolked egg, such as a bird’s egg
- The layer of cells formed by the cleavage of a fertilized mammalian egg, which later divides into the three germ layers from which the embryo develops.germinal membrane germ membrane