Human ovum is covered by 3 membranes. namely-
(i) Corona radiata: The outermost layer of ovum is called corona radiata. In amphibians it is jelly-like. In birds it is complex in nature and has four layers.
(ii) Zona pellucida: The inner layer of corona radiator is called zona pellucida. It has a protective coating.
(iii) Vitelline: The innermost layer of the envelope is called vitelline. It covers the cytoplasm.