Virtually no growth. Stage of inactive embryonic life During Incubation Day 1 Development of area pellucida and area opaca of blastoderm. Blood vessels appear in the yolk sac.
Amnion completely surrounds embryo.
Day 4 Formation of tongue begins. Embryo completely separate from yolk sac and turned on left side. Allantois breaks through amnion. Day 5 Proventriculus and gizzard formed. Formation of reproductive organs and sex determined.