This is the four cell stage. Four equal-sized blastomeres are the end result. Later The eight cell stage. The thirty-two cell stage is seen here. After the 16 cell stage, the cleavages become more difficult to follow, due to the increasing number of cells and to the division of blastomeres becoming asynchronous.
Cleavage continues, forming a mass of cells which organizes itself into the blastula.
The lighter area in the centre of the embryo is the beginning of the blastocoel. Later This shows the early blastula. This blastocoel is surrounded by a single layer of cells, forming the hollow sphere know as the blastula. This shows the late blastula. The blastomeres are seen to be smaller and are individually not as obvious.