Haekel's law of Recapitulation, palingenesis

Haekel's law of Recapitulation, palingenesis

or

von Baer's law

a law stating that ONTOGENY recapitulates PHYLOGENY. This means that an organism will go through embryonic stages similar to those gone through during its evolutionary development. For example, mammals have a fish-like stage in their embryology. The law was formulated by the German biologist Ernst Haekel (1834–1919).
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005