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Hamburger and Hamilton Stage 28

HH28 (5.5-6 days).
Second digit and third toe slightly longer than others.
Three digits and four toes distinct.
No fifth toe.
Protuberance 'a' still projects over surface.
Mandibular process has lengthened and grown forward.
Parts 'b' and 'e' have fused.
'b', 'd' and 'e' no longer project above surface.
External auditory opening now very distinct between 'a', 'b' and 'd'.
'Collar' ('f') projects distinctly over surface.
Neck between 'collar' and mandible lengthened.
Beak: distinct outgrowth visible in profile.


  1. TXT - Text Format
    The ABSTRACT ONTOLOGY (NOT Staged/Timed) with all pathways to child nodes materialised, in Plain Text only, as a Tree Report.

  2. OBO - OBO Format
    The ABSTRACT ONTOLOGY (NOT Staged/Timed) in OBO Flat File Format, version 1.2, available for viewing/editing using OBO-Edit.


  1. H. Eyal-Giladi and S. Kochav
    From cleavage to primitive streak formation: A complementary normal table and a new look at the first stages of the development of the chick : I. General morphology
    Developmental Biology, Volume 49, Issue 2, April 1976, Pages 321-337

  2. V. Hamburger and H.L. Hamilton
    A series of normal stages in the development of the chick embryo
    Journal of Morphology, 1951, Volume 88, Pages 49-92 (reprinted in Developmental Dynamics, December 1992, Volume 195, Issue 4, pages 231-72)

  3. R. Bellairs and M. Osmond
    The Atlas of Chick Development
    Academic Press, ISBN 0-12-084790-6, 1998

  4. C.D. Stern and P.W.H. Holland (Ed.s)
    Essential Developmental Biology: A Practical Approach
    Oxford University Press, ISBN 0-19-963423-8, 1993

  5. M.A.J. Selleck and C.D. Stern
    Fate mapping and cell lineage analysis of Hensen's node in the chick embryo
    Development, Volume 112, Pages 615-626, 1991