The document discusses the embryonic and evolutionary development of the urogenital system in vertebrates. It describes the three primitive kidney types - pronephros, mesonephros and metanephros. The pronephros is the first to develop and later involutes. The mesonephros functions as the adult kidney in fish and amphibians. In amniotes, the mesonephros is replaced by the metanephros. The document also covers the differentiation of sexual structures in embryos and lists homologous structures between male and female urogenital systems.