The ectodermal cells overlying the notochord differentiate to form Neuroectoderm. Neuroectodermal cells proliferate and form the neural tube. Cells at the junction of neuroectoderm and ectoderm differentiate to form neural crest cells, which lie on dorsolateral aspect of neural tube. Derivatives of neural crest cells: (i) Dorsal root ganglia of spinal nerves, (ii) Cranial nerve ganglia, (iii) Sympathetic and parasympathetic ganglia, (iv) Schwann cells, (v) Cells of adrenal medulla, (vi) Melanoblast of skin, (vii) Leptomeninges (pia and arachnoid mater), (viii) Derivatives of pharyngeal arch (skeletal and muscular elements), (ix) Divisions of neural tube, and (x) Cranial dilated part (brain vesicle), which forms the brain. Caudal tubular part, which forms the spinal cord. Parts of brain vesicle and their derivatives: (i) Telencephalon: Cerebral cortex, white mater of cerebrum and basal nuclei, (ii) Diencephalon: Thalamus, hypothalamus, epithalamus, subthalamus and metathalamus, (iii) Mesencephalon: Mid brain. (iv) Metencephalon: Pons and cerebellum, and (v) Telencephalon: Medulla. Ventricular system of C.N.S.: (i) Telencephalon: Lateral ventricle, (ii) Diencephalon: Third ventricle, (iii) Mesencephalon: Cerebral aqueduct, (iv) Metencephalon and Telencephalon: Fourth ventricle, and (v) Caudal tubular part of neural tube: Central canal of spinal cord. Histogenesis of neural tube. Single layered neural tube is converted into three layered structure as follows: (i) Germinal layer forms ependymal layer, (ii) Mantle layer forms grey mater, (iii) Marginal layer forms white mater. Pituitary gland: The pituitary gland develops from two sources: (i) From the roof of stomodeum a diverticulum called as Rathke’pouch is formed. It gives rise to pars anterior, pars tuberalis and pars intermedia of pituitary gland (Adenohypophysis) and (ii) Infundibulum a downward projection from diencephalon forms pars posterior and stalk of pituitary gland (Neurohypophysis).