Tracking Analysis of NCC Migration. The migration patterns of two closely distributed NCC populations (a, b), and the graphs of the distribution of the migration velocities of NCCs from the two populations (c, d). (a) Population I derived from the most posterior part of the midbrain and migrated. towards the maxillary process and the eye (n = 5). (b) Population II derived from the most anterior part of the hindbrain and went to the first. branchial arch (n = 5). (c) The migration velocity distribution of population I. (d) The migration velocity distribution of population II.