An early form of an embryo undergoing developmental processes, such as cleavage. It is marked by the presence of blastocoel and cells made up of around 128 cells.
Blastula contains a fluid-filled blastocoel surrounded by layers of cells that emerge from series of cleavage. The process involved in the formation of blastula is referred to as blastulation.
Word origin: from Greek blastos, bud + Latin -ula