1. In the first diagram, the middle red layer is highlighted and labeled notochord. The blue cells above the red band of cells are captioned ‘Part of the ectoderm thickens and forms the neural plate.’
2. In the second diagram, neural folds are labeled.
3. In the third diagram, the neural crest and neural folds are labeled.
4. In the last diagram, the neural tube, neural crest, ectoderm and notochord are labeled.