In earthworm, brain is represented by cerebral ganglia located

Cerebral ganglia are dorsal to the pharynx in the earthworm.

The nerve cord in the anterior region (3^rd and 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 responses of the body.