Recapitulation theory
The theory of recapitulation, also called the biogenetic law or embryological parallelism— usually summarized as "ontogeny recapitulates phylogeny"— is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (ontogeny), goes through stages resembling or representing successive adult stages in the evolution of the animal's remote ancestors (phylogeny). It was formulated in the 1820s by Étienne Serres based on the work of Johann Friedrich Meckel, after whom it is also known as the Meckel–Serres law.