 |
 |
 |
| fertilized egg (zygote) |
2-cell stage |
4-cell stage |
 |
 |
 |
| 8-cell stage | morula | blastula |
 |
 |
 |
| blastula | blastula | gastrula |
| Number |
Structure |
| 1 |
blastocoel (cavity) |
| 2 |
ectoderm |
| 3 |
mesoderm |
| 4 |
endoderm |
| 5 |
blastopore |
| 6 |
archenteron |
