Cells formed by cleavage of a fertilized ovum is known as blastomere . These blastomeres together are called Blastula .

In the initial stage of development, the blastomeres adhere to each other in a mass called a morula . ( which is shown as 1 ) . The 2nd stage is called blastocyst which is formed when the ovum gets attached to the uterine wall . The intermediate stage you see between 1 and 2 is called Blastula .