| Eventually these cells fill the blastocoel and form a compact mass of endoderm. |
| The outer layer of cells is called the blastoderm, and the fluid-filled cavity the blastocoel. |
| At gastrulation, the germ plasm is located in cells in the floor of the blastocoel cavity, among the cells that give rise to the endoderm. |
| The blastomeres then may be arranged as a saucer-shaped blastodisk covering the blastocoel. |
| The central part of the blastosphere is called the segmentation cavity or blastocoel. |
| The blastocoel appears bright grey, the animal cap darker-gray and the vegetal pole black. |
