Axonal sorting and myelination are impaired in ILK mutant SNs. (a–l) 0.5-µm SN cross sections stained with Toluidine blue. Early in development (a–f), SCs are in close association with bundles of naked axons (c–f; asterisks). (c and d) Progressively individual axons are sorted from these bundles in a process referred to as radial sorting (arrowheads). (g, i, and k) In control nerves, individual large caliber axons are wrapped and myelinated. (h, j, and l) In the mutant nerves, radial sorting and myelination are impaired, and axon bundles persist into adulthood. Bars, 10 µm.