metagenesis

Definitions

  • WordNet 3.6
    • n metagenesis alternation of sexual and asexual generations
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Webster's Revised Unabridged Dictionary
    • Metagenesis (Biol) Alternation of sexual and asexual or gemmiparous generations; -- in distinction from heterogamy.
    • Metagenesis (Biol) The change of form which one animal species undergoes in a series of successively produced individuals, extending from the one developed from the ovum to the final perfected individual. Hence, metagenesis involves the production of sexual individuals by nonsexual means, either directly or through intervening sexless generations. Opposed to monogenesis. See Alternate generation, under Generation.
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Century Dictionary and Cyclopedia
    • n metagenesis In biol, that modification of parthenogenesis or alternate generation which is exhibited when an organism passes from the egg to the imago through a series of successively generated individuals differing from one another in form: distinguished by Owen from metamorphosis, or the transformation of any one individual by the modification of its form as a whole. Metagenesis of one or another kind is exhibited by some insects, as aphids, in which the process is commonly called parthenogenesis; by various internal parasites, as Distoma (see cuts under cercaria); and strikingly by various hydrozoans. In the last the cycle includes the free-swimming impregnated ovum; the fixation of this ovum to some submerged object and its development into an organism; the formation by such organism of various zoöids, as nutritive and generative zooids, unlike each other and unlike the parent, the whole forming a hydroid colony; and the formation by generative zooids of ova, which on being set free complete the cycle. Thus, in a sertularian polyp the ovum is a free-swimming ciliated body, which on fixation develops a mouth and tentacles, and by continued gemmation produces two sets of buds, of which the generative set reproduce the free-swimming ciliated ova. In other polyps, as Corynidæ, the set of generative buds themselves become detached as free medusoids like jelly-fish (see cut under medusnid), whose eggs develop not into bodies like the parent medusoid, but into the polypide or polypidom of the hydroid colony on which they were produced. In the Lucernaria a similar metagenesis occurs by fission. Herbert Spencer adopts Owen's metagenesis as one of three kinds of his agamogenesis, and considers it as external, where new individuals bud from unspecialized parts of the parent, and internal, as in the case of the transformations of Distoma. See metamorphosis.
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Chambers's Twentieth Century Dictionary
    • n Metagenesis met-a-jen′e-sis (biol.) a kind of alteration of generations in which a series of generations of unlike forms come between the egg and the parent type
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Etymology

Webster's Revised Unabridged Dictionary
Pref. meta-, + genesis,

Usage

In literature:

CIRRIPEDES, metagenesis in, ii.
"The Variation of Animals and Plants Under Domestication, Volume II (of 2)" by Charles Darwin
Hence the alternation is of the type termed metagenesis.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 2" by Various
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