Early in development, the nervous system begins as a tube surrounding a
fluid-filled cavity.
The tube which surrounds the fluid-filled cavity is referred to as neural tube.
The tube gives rise to the central and peripheral nervous system as
development occurs.
The inner part of the tube thickens to form the central nervous system
which consists of the brain and spinal cord while the outer region forms
the peripheral nervous system.
Read more on https://brainly.com/question/869589
