Across
- 5. series of air-filled cavities
- 6. small openings
- 9. embryonic development
- 10. egg shell
Down
- 1. living substance of the egg
- 2. invagination of mesoderm and endoderm
- 3. lifeless food material
- 4. fusion of sperm and egg cell
- 7. first stage of development
- 8. supports the embryonic development