blastula: 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
embryo: 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
saturated fatty acid: a fatty acid whose carbon chain cannot absorb any more hydrogen atoms; found chiefly in animal fats