Burnham of Boston, a naturalist of rare sagacity, who told him that naturalists were wrong in asserting metagenesis in the case of aphides.
We merely note that the author insists on metagenesis as well as parthenogenesis, that is, that the offspring may differ in kind from the parents, and that there are virgin, or rather, sexless mothers.
I assured him that if he would take the pains to observe more closely he would find that his metagenesis and parthenogenesis are only different stages in the entire process of the reproduction of the aphid.
While in real metagenesis (alternation of generations in the strict sense) the asexual generation propagates by budding or spore-formation, this is done parthenogenetically in the cognate process of heterogenesis.
This special form of metagenesis was the first to be observed, as it was in 1819 by the poet Chamisso, when he sailed round the world.
But the process resembles metagenesis in so far as the ontogenetic construction consists itself in a repeated division of the cells.
When the latter is combined with asexual reproduction, as is especially the case with the Hydrozoa, metagenesis may be derived therefrom.
The conclusion seems inevitable that metagenesis has here proceeded from metamorphosis; that is to say, one stage of the ontogeny, by acquiring asexual propagation, has changed the originally existing metamorphosis into metagenesis.
A third way in which metagenesis might originate is through polymorphosis.
Haeckel alone has quite recently subjected these complicated phenomena generally to a searching investigation, and has arrived at the conclusion that the various forms of metagenesis can be arranged in two series.
Metagenesis takes its origin from a phyletic series of dissimilar forms, whilst heterogenesis originates from a phyletic series of similar forms--this series, so far as we can at present judge, always consisting of similar sexual generations.
We should then be inclined to regard these generations as an earlier phyletic stage, whilst, in fact, they would be a later one, and the idea of metagenesis would thus have been formed after the manner of heterogenesis.
But if we exclude heterogenesis there still remain a large number of cases of true metagenesis which cannot be explained from this point of view.
In Trachylinae also the beginnings of a similarmetagenesis can be found.
It will be seen elsewhere, however, that whatever view may be held as to the origin of metagenesis in Hydromedusae, in the case of Scyphomedusae (q.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "metagenesis" in a variety of sentences. We hope that you will now be able to make sentences using this word.
