Blastula and Conceptus

Blastula noun - Early stage of an embryo produced by cleavage of an ovum; a liquid-filled sphere whose wall is composed of a single layer of cells; during this stage (about eight days after fertilization) implantation in the wall of the uterus occurs.

Conceptus and blastula are semantically related. In some cases you can use "Conceptus" instead a noun "Blastula".

Conceptus noun - An animal organism in the early stages of growth and differentiation that in higher forms merge into fetal stages but in lower forms terminate in commencement of larval life.

Blastula and conceptus are semantically related. Sometimes you can replace term "Blastula" with "Conceptus", this nouns are similar.