1. Figure 19.26 Origin of the Nervous System Process Diagrams Step-by-Step Copyright © 2007 by John Wiley & Sons, Inc.

2. HEAD END TAIL END Neural plate Neural folds Neural tube Neural groove Cut edge of amnion 1. Neural plate Ectoderm Future neural crest Notochord Endoderm 1. Mesoderm (a) Dorsal view

3. HEAD END TAIL END (a) Dorsal view Neural plate Neural folds Neural tube Neural groove Cut edge of amnion 2. 1. Neural folds Neural groove Endoderm 2. Neural crest Ectoderm Somite Notochord Neural plate Ectoderm Future neural crest Notochord Endoderm 1. Mesoderm

4. HEAD END TAIL END Neural plate Neural folds Neural tube Neural groove Cut edge of amnion 2. 1. 3. Neural folds Neural groove Endoderm 2. Neural crest Ectoderm Somite Notochord Neural tube Notochord Endoderm (b) Transverse sections 3. Neural crest Ectoderm Somite Neural plate Ectoderm Future neural crest Notochord Endoderm 1. Mesoderm (a) Dorsal view