morula vs. blastula

noun

Embryology.
plural morulas, morulae
  1. the mass of cells resulting from the cleavage of the ovum before the formation of a blastula.


noun

Embryology.
plural blastulas, blastulae
  1. the early developmental stage of an animal, following the morula stage and consisting of a single, spherical layer of cells enclosing a hollow, central cavity.