The Columbia Encyclopedia, Sixth Edition. 2001-07.
tadpole
larval, aquatic stage of any of the amphibian animals. After hatching from the egg, the tadpole, sometimes called a polliwog, is gill-breathing and legless and propels itself by means of a tail. During the period of metamorphosis it develops the lungs, legs, and other organs of the adult and, in the frog and the toad, loses the tail.