An early stage of embryonic development in animals. 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 the blastocoel. The blastula follows the morula and precedes the gastrula in the developmental sequence.

http://upload.wikimedia.org/wikipedia/commons/c/c6/Blastulation.png

consider adding a preceding stage 'morula stage' as part of cleavage

uberon

UBERON:0000108

http://purl.obolibrary.org/obo/uberon.owl, http://purl.obolibrary.org/obo/cl.owl

• gastrula stage

• blastula
• blastocyst