A blastula is an early embryo that has been formed by cleavage, or subdivision, of a fertilized egg. The fertilized egg, also known as a zygote, undergoes cell division that partitions the zygote into smaller and smaller cells. Blastula formation is...

The blastula is an early stage of embryonic development in animals. It is also called blastosphere. It is produced by cleavage of a fertilized ovum and consists of a spherical layer of around 128 cells surrounding a central fluid-filled cavity called...