Recapitulation (redirected from recapitulations)

recapitulation, theory, stated as the biogenetic law by E. H. Haeckel, that the embryological development of the individual repeats the stages in the evolutionary development of the species. For example, the beginnings of gill clefts appear in both humans and fish, but while they are elaborated and eventually function in the fish, in humans, except for the modified gill cleft that becomes the Eustachian tube, they disappear as the embryo develops. Though drastically modified and qualified since its proposal, the historical significance of this theory—"ontogenesis recapitulates phylogenesis"—is that with its appearance it lent support to the theory of evolution by seeming to corroborate it.

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recapitulation

1. Biology the apparent repetition in the embryonic development of an animal of the changes that occurred during its evolutionary history

2. Music the repeating of earlier themes, esp when forming the final section of a movement in sonata form

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Recapitulation 

in biology, the repetition of the characteristics of remote ancestors in the ontogeny of existing organisms, specifically, in their structures, chemistry, and functions. The recapitulation theory was first formulated in 1859 by C. Darwin. The theory of phylembryogenesis, proposed by A. N. Severtsov, interpreted recapitulation in more morphological terms. The modern recapitulation theory was elaborated by I. I. Shmal’gauzen.

Recapitulation depends on the presence of a complex system of correlations in the organism and frequently manifests itself in the developmental peculiarities of interrelated organs and structures. Recapitulation results from shifts in the final formative stages of certain organs and not of the organism as a whole. These shifts represent extensions that arise from new correlations, which are introduced in ontogeny after the realization of basic morphogenetic processes.

There are many examples of recapitulation. In the embryos of land vertebrates, gill slits develop that correspond to the gill slits of their fishlike ancestors. In the ontogeny of higher vertebrates the succession of pronephros, mesonephros, and meta-nephros recapitulates the sequence of development of excretory organs in the phylogeny of their ancestors. In pteridophytes the dichotomous branching of their first fronds recapitulates the di-chotomous branching characteristic of their ancestors-Paleozoic psilophytes. During metamorphosis, the vision of frogs is dependent on the use of vitamin A₂, just as in freshwater fish. By the time metamorphosis is completed, their vision is dependent on the use of vitamin A₁, which is characteristic of land vertebrates.

REFERENCES

Severtsov, A. N. Morfologicheskie zakonomernosti evoliutsii, Moscow-Leningrad, 1939.
Shmal’gauzen, I. I. Organizm, kak tseloe ν individual’nom i istoricheskom razvitii. Moscow-Leningrad, 1938.
Mirzoian, E. N. Razvitie ucheniia o rekapituliatsii. Moscow, 1974.

E. N. MIRZOIAN