The embryo at the 16-celled stage is called the morula. It is the mass of cells resulting from the cleavage of the ovum before the formation of a blastula.
Blastomere is any cells produced during cleavage.
Blastula is the early development stage of a metazoan, following the morula stage and consisting of a single, spherical layer of cells that encloses a hollow, central cavity.