Before Egg Laying
|
- Fertilization
- Division and growth of living cells
- Segregation of cells into groups of special function (gastrulation)
|
Between Laying and Incubation
|
Virtually no growth. Stage of inactive
embryonic life |
During Incubation
|
Day
1
Development of area pellucida and area opaca of blastoderm.
Major developments visible under microscope:
- 18 hours, appearance of alimentary tract
- 19 hours, beginning of brain crease
- 20 hours, appearance of vertebral column
- 21 hours, beginning of formation of brain and nervous system
- 22 hours, beginning of formation of head
- 23 hours, appearance of blood islands
- 24 hours, beginning of formation of eyes
|
Day
2
Embryo begins to turn on left side.
Blood vessels appear in the yolk sac.
Major developments visible under microscope:
- 25 hours, beginning of formation of veins and heart
- 30 hours, second, third and fourth vesicles of brain clearly
defined, as is heart, which now starts to beat
- 35 hours, beginning of formation of ear pits
- 36 hours, first sign of amnion
- 46 hours, formation of throat
|
Day
3
Formation of nose, wings, legs, and allantois begins.
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.
|
Day
6
Formation of beak and egg-tooth begins.
Main division of legs and wings.
Voluntary movement begins.
|
Day
7
Indications of digits in legs and wings are visible.
Abdomen more prominent due to development of viscera.
|
Day 8
Formation of feathers begins.
|
Day 9
Embryo begins to look bird-like.
Mouth opening appears.
|
Day
10
Beak starts to harden.
Skin pores visible to naked eye.
Digits completely separated.
|
Day
12
Toes fully formed.
First feathers appear.
|
Day
13
Scales and claws appear.
Body fairly well covered with feathers.
|
Day 14
Embryo turns its head towards blunt end of egg.
|
Day
15
Small intestines taken into body.
|
Day
16
Scales, claws and beak becoming firm and horny.
Embryo fully covered with feathers.
Albumen nearly gone and yolk increasingly important as nutrient.
|
Day 17
Beak turns toward air cell, amniotic fluid decreases, and embryo
begins preparation for hatching.
|
Day
18
Growth of embryo nearly complete.
|
Day 19
Yolk sac draws into body cavity through umbilicus.
Embryo occupies most of space within egg except air cell.
|
Day
20
Yolk sac completely drawn into body cavity.
Embryo becomes chick, breaks amnion, starts breathing air in air
cell
Allantois ceases to function and starts to dry up.
|
Day
21
Chick hatches!
|