A theoretical explanation is provided for decussations in the Central Nervous System at several levels, characteristic positions of gray matter in the spinal cord and the cerebral hemispheres, contralateral control of cerebral hemispheres and the partial crossing of fibers in the optic chiasma. The explanation also covers formation of corpus callosum, positions of visual and olfactory cortices, positions of auditory and vestibular centers and the position of basal ganglia, superior colliculus and the cerebellar nuclei.