Fig. 3.

Schematic drawings of right hemisections through the hindbrain illustrating secondary morphogenesis in NL (dorsal toward the top). By E19, NM, NA, and NL were readily identified, although their limits still lay in close proximity in more caudal sections. The cells of the more caudolateral, low best frequency regions of NL were organized in a lamina typical of basal birds. In more rostromedial regions, however, cells in NL had begun to migrate away from the center of the lamina and fill the NL neuropil. This separation progressed toward more caudolateral regions such that by E24 this separation was evident in more caudal sections. ByE31, close to hatching, the distribution of cells within NL was comparable to that seen in the adult, with cells occupying the entire nucleus all the way to the edges, although the nucleus had not yet reached its adult size. During the first 3 weeks after hatch, growth of NL was characterized by an increase in thickness that results in further separation of the NL cells. VIII, Cochleovestibular nerve; RL, rhombic lip;NA, nucleus angularis; NM, nucleus magnocellularis; NL, nucleus laminaris; NL lat, lateral region of the nucleus laminaris.