This is the same time-lapse sequence that we examined in the section on gastrulation, but now the focus will be on the later stages of morphogenesis during neurulation in Xenopus. Neurulation here is very similar to that in urodeles, including neural fold elevation and invagination of the neural plate to form the neural tube. Also note the elongation of the neural axis as neurulation proceeds. This results from the convergence and extension of the non-involuting marginal zone (NIMZ). This seems to be analagous to the elongation of the "notoplate" described by Jacobson and Gordon in urodeles. The convergence and extension behavior can be studied in Keller sandwiches, and appears to be predicated upon planar inductive signals that originate in the dorsal involuting marginal zone.
