CONTENTS

• Abstract
  
• Introduction
  
• Organization
  
• Procedures
  
• Temperature and Standard Developmental Time
  
• Zygote Period (0-3/4 h)
  
• Cleavage Period (0.7- 2.2 h) Description and Stages
  
• Blastula Period (2 1/4 - 5 1/4 h) Description and Stages
  
• Gastrula Period (5 1/4 - 10 h) Description and Stages
  
• Segmentation Period (10-24 h) Description and Stages
  
• Pharyngula Period (24-48 h) Description and Stages
  
• Hatching Period (48-72 h) Description and Stages
  
• Glossary
  
• References

• Fig. 1. Camera lucida sketches of the embryo at selected stages.
  
• Fig. 2. Rates of development for embryos incubated at 25C and 33C.
  
• Fig. 3. The zygote period.
  
• Fig. 4. Embryos during the cleavage period.
  
• Fig. 5. Idealized blastomere number as a function of time.
  
• Fig. 6. Diagrammatic animal polar views of the planes of the first 5 cleavages.
  
• Fig. 7. Camera lucida drawings of face views during cleavage, showing lineal relationships of the blastomeres from the 4-cell stage through the 64-cell stage.
  
• Fig. 8. Face views of embryos during the blastula period.
  
• Fig. 9. Cell cycle lengthening and loss of synchrony at the midblastula transition..
  
• Fig. 10. Formation of the yolk syncytial layer viewed with Nomarski optics.
  
• Fig. 11. Development during the gastrula period.
  
• Fig. 12. Idealized rate of advance of the blastoderm margin over the yolk cell during epiboly.
  
• Fig. 13. The dorsal side of the blastoderm in a midgastrula embryo, at the 75%-epiboly stage.
  
• Fig. 14. Fate map of the deep cell layer at gastrula onset, at the 50%-epiboly stage before formation of the germ ring and hypoblast.
  
• Fig. 15. Development during the segmentation period.
  
• Fig. 16. Embryo length as a function of time of development.
  
• Fig. 17. Somite morphogenesis.
  
• Fig. 18. Idealized rate of somitogenesis.
  
• Fig. 19. Demonstration with lineage tracer that somite 3 makes myotome 3.
  
• Fig. 20. Pronephric duct morphogenesis near the region where the anus forms.
  
• Fig. 21. The neural tube forms by cavitation.
  
• Fig. 22. Early morphogenesis of the neural primordium.
  
• Fig. 23. Sculpturing of the brain rudiment during the segmentation period.
  
• Fig. 24. The optic primordium is well formed at the 9-somite stage (13.5 h).
  
• Fig. 25. Rhombomeres 2-6 at the 18-somite stage (18 h).
  
• Fig. 26. Cells of the trigeminal placode will form sensory neurons of the trigeminal ganglion.
  
• Fig. 27. Morphogenesis of the otic vesicle.
  
• Fig. 28. Tail development.
  
• Fig. 29. Development during the pharyngula period.
  
• Fig. 30. Neural structures predominate in the head during the pharyngula period.
  
• Fig. 31. The pharyngeal arch primordial region at the prim-25 stage (36 h).
  
• Fig. 32. Cells of the hatching gland, present on the pericardium over the anterior yolk sac have prominent granules during the pharyngula period.
  
• Fig. 33. Head-trunk angle as a function of hours of development (at 28.5C).
  
• Fig. 34. The posterior lateral line primordium, and underlying structures along the flank of the pharyngula.
  
• Fig. 35.Prim number as a function of hours of development (at 28.5C).
  
• Fig. 36. Condensing mesenchyme of the early pectoral fin bud.
  
• Fig. 37. Morphogenesis of the pectoral bud during the late pharyngula period.
  
• Fig. 38. Refractile tail reticular cells line sinusoids that make up the wall of the developing caudal vein.
  
• Fig. 39. Development during the hatching period of embryogenesis and the early larva.
  
• Fig. 40. The embryo's small open mouth (arrow) lies between the two eyes at the pec-fin stage (60 h).
  
• Fig. 41. Jaw cartilage and muscle formation is well underway by the end of the hatching period.
  
• Fig. 42. Branchial arches develop late in embryogenesis.
  
• Fig. 43. The appearance of the cleithrum, the first easily visible bone, marks the end of embryogenesis.