Write notes on nervous system and the sensory system in earthworm.

Nervous system: It is basically represented by ganglia arranged segment- wise on the ventral paired nerve cord.

The nerve cord in the anterior region i.e. 3^rd & 4^th segments bifurcates laterally encircling the pharynx and joins the cerebral ganglia dorsally to form a nerve ring. The cerebral ganglia along with other nerves in the ring integrate sensory input as well as command muscular response of the body.

Sensory System: It does not have eyes but possesses light and touch sensitive organs (receptor cells) to distinguish the light intensities and to feel vibrations in the ground.

Earthworms have special chemo–receptors which react to chemical stimuli. These sense organs are located on the anterior part of the body.