The Central Nervous System of Leech consists of a nerve ring and a paired ventral nerve cord. The nerve ring surrounds the Pharynx and is formed of Suprapharyngeal ganglion (brain), Circum pharyngeal connective and Subpharyngeal ganglion. The Subpharyngeal ganglion lies below the Pharynx and is formed by the fusion of four pairs of Ganglia.
