Section 18. Figure 7 I. Is a Dorsal View of the Gastrula At a Somewhat

later stage, and here indications of distinctly vertebrate relationships already appear. Figure 7 ii. is a cross-section, its position, being shown by cross-lines in 7 i. and 6. Note first that the epiblast along the mid-dorsal line is sinking in to form what is called the neural plate (n.p.), and simultaneously on either side of it rise the neural folds (n.f.). Now, at Figure 8, a slightly later stage is represented, and at 9 i. the inturned part is separated from the general external epiblast as the spinal cord. The remainder of the epiblast constitutes the epidermis.