distingiush b/w morula gastrula and blastula

Embryo with 8 to 16 celled stage is called morula.

Blastula is a stage of embryonic development, followed by morula, consisting of single layer of cells. During this stage embryo is attached to uterus through the process of implantation. 

Blastula is followed by gastrula stage. Gastrula consists of two or more germ layers which in later stages of development give rise to different organs.