| It is desirable only further to explain that gastrulation does not take place in all the Metazoa after exactly the same plan. |
| Using explanted tissues from embryos of different ages, it has been shown that mesoderm induction is almost complete by the time gastrulation starts. |
| Special focus has been on the pattern of early cleavage, blastoderm and germinal disc development and gastrulation. |
| Covered with cilia, the sea-urchin blastula swims in the water and proceeds with gastrulation. |
| At the end of gastrulation, the epidermis only covers the dorsal region and the ventral region is bare. |
| After the blastula develops, it undergoes transition to the gastrula, a process called gastrulation. |
