stageschick

 

Staging series for embronic chick development
from laying to 6 days of incubation (at 38°C)

(After Hamburger and Hamilton, 1951)

Stage Length of incubation Description of embryo

Stage 1:
Prestreak

 0 After laying, cleavage is complete and gastrulation has begun, but the primitive streak has not yet formed.

Stage 2:
Initial streak

 6–7 hours First formation of the primitive streak.

Stage 3:
Intermediate streak

12–13 hours A broad streak has formed that extends from the posterior margin to the center of the area pellucida.

Stage 4:
Definitive streak

18–19 hours The primitive streak extends about three–quarters the length of the area pellucida, which is now pear-shaped. Hensen’s node is present.

Stage 5:
Head process

 19–22 hours The notochord is visible, but the head fold has not yet formed.

Stage 6:
Head fold

 23–25 hours Anteriorly, the head fold is distinct. No somites have formed yet.

Stage 7:
1 Somite

 23–26 hours One pair of somites can be seen, and the neural folds are visible anteriorly.

Stage 8:
4 Somites

 26–29 hours Four pairs of somites are present. Neural folds meet at the level of the midbrain, and blood islands are seen in the area vasculosa.

Stage 9:
7 Somites

 29–33 hours Seven pairs of somites. The optic vesicles are forming, and the heart is beginning to form.

Stage 10:
10 Somites

 33–38 hours 10 pairs of somites. Three major subdivisions of the brain are visible. Heart is bent slightly to the right.

Stage 11:
13 Somites

 40–45 hours 13 pairs of somites. Five neuromeres of the myelencephalon can be seen. Anterior neuropore is closing.

Stage 12:
16 Somites

 45–49 hours 16 pairs of somites. Head is turning to the left. Optic placode is invaginating.

Stage 13:
19 Somites

 48–52 hours 19 pairs of somites. Head is turned almost fully to the side.

Stage 14:
22 Somites

 50–53 hours 22 pairs of somites. Body is rotated to the side as far back as 7–9 somites First two pharyngeal pouches and grooves are distinct. Optic vesicles invaginating.

Stage 15:
Optic cup

 50–55 hours 24–27 pairs of somites. The third pharyngeal pouch and groove have formed. The optic cup is formed.

Stage 16:
Pre-limb bud

 51–56 hours 26–28 pairs of somites. Tail bud is beginning to form.

Stage 17:
Early limb bud

52–64 hours 29–32 pairs of somites. Both wing and leg buds are distinct swellings. Tail is bent ventrally. Allantois not yet present.

Stage 18:
Early allantois

 3 days 30–36 pairs of somites. Limb buds have enlarged. Tail bud has turned to the right. Allantois is a thick-walled pocket.

Stage 19:
Somites in tail

 3–3 1/2 days 37–40 pairs of somites, which extend into the tail. Leg bud is slightly larger than wing bud. Eyes are unpigmented.

Stage 20:
Vesicular allantois

 3–3 1/2 days 40–43 pairs of somites. Leg bud slightly asymmetrical. Allantois vesicular, about the size of the midbrain.

Stage 21:
Early eye pigmentation

 3 1/2 days 43–44 pairs of somites. Both wing and leg buds slightly asymmetrical. Allantois enlarged. Eye pigmentation faint.

Stage 22:
Distinct eye pigmentation

3 1/2–4 days Somites extend to tip of tail. Eye pigmentation is distinct.

Stage 23:
Limb buds as wide as long

 4 days Both wing and leg buds are as wide as they are long.

Stage 24:
Limb buds longer than wide

 4 1/2 days Both wing and leg buds are distinctly longer than they are wide. Toe plate is distinct, but toes are not yet demarcated.

Stage 25:
Early elbow and knee

 4 1/2–5 days The elbow and knee joints are distinct. The digital plate in the wing is distinct but with no demarcation of digits. Third toe is demarcated by a faint groove.

Stage 26:
Three toes

 5 days Limbs are considerably longer. The demarcation of three toes is distinct. There is a faint groove between the second and third digit of the wing.

Stage 27:
Early beak

 5–5 1/2 days The three digits of the wing are demarcated by grooves. The beak is just recognizable.

Stage 28:
Beak distinct

 5 1/2–6 days The second digit of the wing and the third toe are longer than the rest. The three wing digits and four toes are distinct. (Chickens only have three “fingers” and four toes.) The beak is a distinct outgrowth.
Source: After Hamburger, V., and H. L. Hamilton, 1951. A series of normal stages in the development of the chick embryo. J. Morphol. 88: 49–92.