part of preceded by neurula stage NF stage 13 NF stage 14 XAO:1000024 xenopus_developmental_stage Nieuwkoop and Faber stage 14, corresponding to an embryo of age 16 hr 15 min at 22-24 Celsius and having the following external morphological criteria: Neural plate stage. Cerebral part of neural plate bent downwards, with median elevation at rostral end of median groove. Initial elevation of neural folds, most pronounced in future nucal region. Blastopore always slit-shaped. Length: 1.5 - 1.6 mm. NF stage