Eyal-Giladi and Kochav, Hamburger Hamilton Stage Definition

This table details some of the defining features of each stage:

Stage Summary Ontology Models Source Movies Wholemounts
EGK-I 0-1 hours uterine age.
Germinal disc 3.
5-4 mm diameter.
EGK-II 2 hours uterine age.
EGK-III 3-4 hours uterine age.
Germinal disc slightly thickened.
EGK-IV 5 hours uterine age.
Upper and lower layers distinguishable.
EGK-V 8-9 hours uterine age.
Sub-germinal cavity stretches to the periphery of the blastodisc.
EGK-VI 10-11 hours uterine age.
Entire cytoplasmic mass of disc is cleaved on both surfaces.
EGK-VII 12-14 hours uterine age.
The posterior region of upper layer becomes thinner and is first sign of area pellucida.
EGK-VIII 15-17 hours uterine age.
Thinner region (developing area pellucida) becomes sickle-shaped.
EGK-IX 17-19 hours uterine age.
Developing area pellucida spreads in an anterior direction.
EGK-X Fresh laid egg.
Area pellucida present.
ECA:27 UCL N/A Wholemounts
EGK-XI Posterior Koller's sickle visible.
EGK-XII Hypoblast covers half of lower surface of area pellucida. ECA:28 UCL N/A Wholemounts
EGK-XIII Hypoblast formation complete. ECA:26 UCL N/A Wholemounts
EGK-XIV Anterior hypoblast has a defined edge.
Posterior 'cellular bridge' visible.
ECA:25 UCL N/A Wholemounts
HH01 OBSOLETE N/A N/A N/A N/A N/A
HH02 Primitive streak is short conical thickening. ECA:24
ECA:38
UCL N/A Wholemounts
HH03 Primitive streak extends to centre of embryo. ECA:23
ECA:22
UCL
UCL
N/A
N/A
Wholemounts
HH04 Hensen's node present. ECA:21 UCL N/A Wholemounts
HH05 Notochord (head-process) is visible. ECA:29
ECA:30
UCL
UCL
N/A
N/A
Wholemounts
HH06 Anterior head fold starts to form. ECA:20 UCL N/A Wholemounts
HH07 1 somite. ECA:31 UCL N/A Wholemounts
HH08 4 somites. ECA:19 UCL N/A Wholemounts
HH09 7 somites. ECA:32 UCL N/A Wholemounts
HH10 10 somites.
3 brain vesicles visible.
ECA:33 UCL N/A Wholemounts
HH11 13 somites.
5 neuromeres in hindbrain.
Heart bent to right.
ECA:34 UCL N/A Wholemounts
HH12 16 somites.
Head starts turning to left.
ECA:35 UCL N/A Wholemounts
HH13 19 somites.
Telencephalon becomes enlarged.
ECA:36 UCL N/A Wholemounts
HH14 22 somites.
Forebrain at a right angle to hindbrain.
ECA:37 UCL N/A Wholemounts
HH15 24-27 somites.
Optic cup completely formed.
ECA:18 Roslin Movies Wholemounts
HH16 26-28 somites.
Tail bud becomes a short, straight cone.
ECA:17 Roslin Movies Wholemounts
HH17 29-32 somites.
Tail bud bent ventrally.
ECA:16 Roslin Movies Wholemounts
HH18 30-36 somites.
Limb buds become enlarged.
Tail bud turned to right.
ECA:12
ECA:15
Bath
Roslin
Movies Wholemounts
HH19 37-40 somites.
Leg buds become slightly larger than wing buds.
Tail bud curved, tip pointing anteriorly.
ECA:11
ECA:14
Bath
Roslin
Movies Wholemounts
HH20 40-43 somites.
Wing buds approximately symmetrical, leg buds slightly asymmetrical.
ECA:10
ECA:9
ECA:8
ECA:13
Bath
Bath
Bath
Roslin
Movies Wholemounts
HH21 43-44 somites.
Both wing and leg buds slightly asymmetrical.
ECA:7
ECA:6
Bath
Bath
N/A N/A
HH22 Eye pigmentation becomes distinct. ECA:5 Bath N/A N/A
HH23 Both wing buds and leg buds approximately as long as they are wide. ECA:4 Roslin N/A N/A
HH24 Both wing buds and leg buds longer than wide.
Toe plate in leg bud becomes distinct.
ECA:3 Bath N/A N/A
HH25 Elbow and knee joints become distinct. ECA:2 Bath N/A N/A
HH26 First three toes become distinct. ECA:1 Bath N/A N/A
HH27 First, second and third digits separated by grooves.
Distinct grooves between toes.
HH28 Three digits and four toes become distinct.
Outgrowth of beak becomes visible.
HH29 Wing bent at elbow.
Rudiments of fifth toe become visible.
HH30 The three segments of wing and leg become clearly demarcated.
Egg tooth becomes distinct.
HH31 Feather papillae on thigh become distinct.
HH32 Rudiment of fifth toe has disappeared.
HH33 Three distinct rows of feather germs in tail, middle row larger than others.
HH34 Differential growth of second digit and third toe is conspicuous.
HH35 Webs between digits and toes are inconspicuous.
Beak becomes lengthened.
HH36 Tapering primordia of claws just visible on termini of toes.
HH37 Lower eyelid covers one-third to one half of cornea.
Upper eyelid has reached dorsal edge of cornea.
HH38 Upper eyelid covered with newly formed feather germs.
Lower eyelid covers two-thirds to three-quarters of cornea.
HH39 Opening between eyelids reduced to a thin crescent.
Covert feathers of web of wing are long, tapering cones.
HH40 Length of beak from anterior edge of nostril to tip of bill = 4.0 mm.
Length of third toe = 12.7 ± 0.5 mm.
HH41 Length of beak from anterior edge of nostril to tip of upper bill = 4.5 mm.
Length of third toe = 14.9 ± 0.8 mm.
HH42 Length of beak from anterior edge of nostril to tip of upper bill = 4.8 mm.
Length of third toe = 16.7 ± 0.8 mm.
HH43 Length of beak from anterior edge of nostril to tip of upper bill = 5.0 mm.
Length of third toe = 18.6 ± 0.8 mm.
HH44 Length of beak from anterior edge of nostril to tip of upper bill = 5.7 mm.
Length of third toe = 20.4 ± 0.8 mm.
HH45 Beak is shiny.
Yolk sac half enclosed in body cavity.
HH46 Newly hatched chick.