The excretory organ of the fetus, which develops into the kidney and is formed from the rear portion of the nephrogenic cord. It does not become functional until birth, since urea is transferred across the placenta to the mother.
The permanent kidney of amniotes (reptiles, birds, and mammals). Part of the metanephros develops from the caudal portion of the intermediate cell mass or nephrotome; the remaining portion is derived from a bud of the mesonephric duct.