1. Early chick embryo

2. Whole Mount of Chick Blastoderm
AO = area opaca, AP = area pellucida
P = region of thick blastoderm that marks the future posterior region of the embryo; area where gastrulation begins
Arrows = movement of rapidly dividing cells of epiblast layer

3. Chick Embryo - Primitive Streak Stage
The primitive streak is the region where epiblast cells converge (solid arrows) and move through a groove into the blastocoel (dashed arrows). The primitive steak consists of a lightly staining groove bordered on each side by darker staining ridges. Hensen's node marks the anterior of the streak and P marks the posterior.
AO = area opaca,
AP = area pellucida,
P= posterior

4. Cross sections through Primitive streak
Key to Upper Cross section:
AO = area opaca
AP = area pellucida
^^ = remnants of yolk granules,
arrows = direction of ingression of embryonic cells
Lower Cross Section shows the three germ layers formed by the process of gastrulation.

5. 24-hr chick embryo
AIP = anterior intestinal portal

6. A Sagittal Section of a 26 Hour Chick Embryo
Prominent neurocoele (neurocoel) in the
Portions of the notochord are visible just ventral to the brain and spinal cord.
Foregut (asterisk) is seen as a cavity extending from the top of the head to the anterior intestinal portal.
Between the foregut and subcephalic pocket is a region of splanchnic mesoderm that will form the heart.
Somites are not visible in this section (the plane of section is between the paired rows of somites).

22. The 33 Hour Chick Embryo - Whole Mount
AIP = anterior intestinal portal

23. Sagittal Section of a 33 Hour Chick Embryo
divisions of the developing brain.
neuromeres in the rhombencephalon.
Neuromeres are segmental divisions of the brain seen in the embryo.
heart forming region is now seen much more clearly
portions of the somites are seen

24. Chick embryo 33 hrs serial cross section

39. 48 Hour Chick Embryo Whole Mount

40. Details of Head

41. 48 Hour Chick Embryo
The brain now consists of five parts or "vesicles". The prosencephalon has divided into two regions, the telencephalon and the diencephalon. The region of the mesencephalon remains as a single unit and retains its name of mesencephalon. The rhombencephalon has become the metencephalon and the myelencephalon. Each of these embryonic parts of the brain will form distinct parts of the adult brain.

42. Details of Pharynx

43. Details of Heart

44. 48 Hour Chick Embryo serial cs

74. 72 Hour Chick Embryo Whole Mount
1 = Telencephalon
2 = Diencephalon
3 = Mesencephalon
4 = Metencephalon
5 = Myelencephalon
* = Otic capsule
^ = Olfactory pit