Online Encyclopedia
Blastula
The blastula is an early stage of embryonic development in animals. It is produced by cleavage of a fertilized ovum and consisting of a spherical layer of cells surrounding a fluid-filled cavity. The blastula follows the morula and precedes the gastrula in the development sequence. A blastula has more than 64 cells, with a large central cavity called the blastocoel. Also called blastosphere .