The tongue of  twelve mature fishes (O. niloticus) was subjected to gross morphological and scanning electron microscopical as well as light microscopical studies. Grossly, the tongue could be divided  into apex, body and root. Scanning electron microscope showed  that there were concentrically arranged fingerprint-like structures on the free surface of the uppermost cell layer of epithelium. Openings with different sizes were demonstrated on the surface of the tongue. It was found that the tongue was covered with stratified squamous nonkeratinized epithelium. The epithelium of the dorsal surface contained numerous large vacuolated mucus- secreting cells with different shapes and sizes. Few taste buds were observed within the epithelium of the dorsal surface of the tongue. The core of the apex contained a central plate of cartilage which was of the fibrous variety rostrally and hyaline type caudally. The core of the body contained three cartilaginous plates; two lateral plates of the hyaline type, which ossified caudally and a single dorso-median plate, which was formed of   large rostral hyaline and small caudal fibro-elastic parts.