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
造句
用作名詞(n.)
The cells of the blastula, called blastomeres, also each receive a full diploid set of chromosomes. 這些囊胚細胞，稱卵裂球，每個細胞都有一套二倍體染色體組。
Cleavage produces a blastula, a sheet of cells rounded into a sphere that in most species surrounds a cavity. 卵裂產生一個囊胚，形成的細胞壁球形排列形成一個空腔。