Recapitulation theory was put forward by E. Haeckel.
Biogenetic law states that ontogeny repeats phylogeny.
Every organism during its development repeats the evolutionary history of its race.
The embryos of the higher animals show resemblances with the adult of lower animals.
Example:
The life history of a frog clearly shows the phylogenetic history. Frog develops through larval stage similar to that of fish.
Man develops through a number of embryonic stages similar to that of the lower animals.
Zygote stage represents the unicellular protozoans.
Blastula and Gastrula represent invertebrates.
Caterpillars look like the adult annelids.
Arthropods developed from annelids.
It is now established that the developmental stages of a higher animal resemble the embryos rather than the adult stage of the lower animals in its phylogeny.