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.