The optic nerve is a tract of the diencephalons that is not completely myeli- nated until

E. The axons of the optic nerve are not completely myelinated until 3 months after birth. Myelinated axons are normally not found in the retina. The optic nerve is not a true peripheral nerve but a tract of the diencephalon; when severed, the optic nerve does not regenerate. Myelination in the central nervous system (CNS) is accomplished by oligoden-drocytes; oligodendrocytes are not found in the retina.