Archinephros
The archinephros is a primitive kidney that has been retained by the larvae of hagfish and some caecilians. It also occurs in the embryos of higher animals as the simplest kind of excretory organ. The archinephros is nonfunctional in humans and other mammals.
The three types of mature vertebrate kidneys develop from the archinephros: the pronephros from the front section, the mesonephros from the mid-section and the metanephros from the rear section.
