Ontogeny recapitulates phylogeny. This is
Mullar proposed 'Recapitulation theory'. According to which 'Ontogeny recapitulates phylogeny'. Ontogeny is the study of embryological development of individual organisms while phylogeny is the evolutionary history of that organism. In 1866, Ernst Haeckel explained it in detail and called it 'Biogenetic law'. It means an organism shows its ancestral adult stages during its embryonic development. So, the correct answer is 'Biogenetic law'.