Biogenetic law states that the higher animals pass through stages of lower animals during their embryonic development. This law is otherwise known as the theory of recapitulation, which states that ontogeny repeats or recapitulates phylogeny. Ontogeny is the life history of an organism and phylogeny is the evolutionary history of a race. According to this law, the embryonic stages of a higher animal resemble its ancestors. For example, pharyngeal gill slits, yolk sac, the appearance of the tail in the human embryo.
This indicates that the human embryo repeats the embryonic history and not the adult history of the organisms. Therefore, the biogenetic law is not universal. It is now thought that animals do not recapitulate the adult stage of any ancestors.
