umm i'm pretty sure the notochord is derived from the mesoderm. it's the neural tube that's derived from the ectoderm. i'm looking at the embryology section from schaum's now. where does it say that notochord comes from ectoderm? Is it under "Primary Germ Layers and Organ Formation" heading? or somewhere else...
under ectoderm, it just says that the nerve tube which is induced by the notochord, the ectoderm also produces the entire nervous system. It doesn't mention anything about the notochord actually being derived from the ectoderm though...
EDIT:
the nervous system is derived from the ectoderm. The development of the nervous system is induced by the effects of the notochord on the nerve tube. i'm pretty sure that's how it works. the actual notochord is derived from mesodermal germ layer