Fig. 1. Microsurgical grafting procedures. The neural tube, including the neural crest, situated between somites 3-6 was excised from chick embryos at 10 ss. Approximately 1 day later, at 25 ss, in the same NC-ablated chick embryos, the sacral region of the neuraxis was excised. The region involved corresponded to the neural tube caudal to the 25th pair of somites (25, arrowhead) and included the chordoneural hinge and rostral region of the tail bud (TB, arrowhead). After excision of the sacral NC, the vagal NC was removed from donor quail embryos at the 10 ss and grafted into the vacant sacral region of the neuraxis, ensuring that the appropriate rostrocaudal/dorsovental orientation was maintained.