RECAPITULATION THEORY / BIOGENETIC LAW
It was proposed by Muller & Haeckel on the basis of Baer's law.
According to it, in the development of animal phylum characters are formed first & species characters are formed in the last.
Hackel proposed recapitulation theory & explained that 'ontogeny repeats phylogeny' i.e. ontogenic development of the animal repeats the evolutionary history of the animal.
"Ontogeny repeats Phylogeny" -
Induction of metamorphosis started by thiourea