| In the third stage the Inner Cell-Mass separates into two layers derived from the inner cell-plate of the blastula. |
| At this stage, the blastula is in the form of a hollow sphere with radial symmetry. |
| Gastrulation in its broadest sense is the reorganization of the cells of the blastula to form a multilayered embryo, the gastrula. |
| A lot of research has gone into answering that, and determining the earliest stage at which the blastula breaks symmetry. |
| When the blastula is oval and free-swimming the inner mass is formed by unipolar immigration from the hinder pole. |
| Our next question concerns the distribution of potentiality, when the embryo is developed further than the blastula stage. |
