On Parthenogenesis; Or, The Successive Production of Procreating Individuals from a Single Ovum: A Discourse Introductory to the Hunterian Lectures on Generation and Development, for the Year 1849, Delivered at the Royal College of Surgeons of EnglandVan Voorst, 1849 - 76 páginas |
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Términos y frases comunes
aggregate alternate analogy animal animalcule Annelides Aphides assimilation body called Cercariæ cercariform chorion ciliated coalesce continuous growth Coryne Dalyell derivative germ-cells detached distinct Distoma division Echinus Ehrenberg embryo Entozoa Entozoon essential condition explain fact flower fluid formation gemmiparous germ germ-cells and nuclei germ-mass germ-yelk germinal vesicle granular Gregarina gregariniform Hydra Hydra Tuba impregnated ovum individual insects integument Kölliker larvæ larval Aphis larviparous Aphis leaf limbs Medusa medusiform ment metamorphosed mode modifications monad monadiform multiplication of cells nature nucleated cells nucleus nutriment observed organs ovarian oviparous oviparous females ovum parent Parthenogenesis pellucid centre phænomena physiologist phytons plant planulæ Pluteus Polygastria polype pregnated primary impregnated germ-cell procreation produced Prof progeny propagated by gemmation resemble result retained Scyphistoma secondary germ-cell Siebold species spermatheca spermatic force spermatic virtue spermatozoon spontaneous fission stamen Steenstrup Strobila Strongyli successive tion tissues trematode unchanged virgin viviparous wet-nurse yelk zoophyte
Pasajes populares
Página 4 - And God said, Let the earth bring forth the living creature after his kind, cattle, and creeping thing, and beast of the earth after his kind: and it was so.
Página 4 - And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good.
Página 37 - ... and, what is most remarkable and without parallel, the sexual intercourse of one original pair serves for all the generations which proceed from the female for a whole succeeding year. Reaumur has proved that in five generations one Aphis may be the progenitor of 5,904,900,000 descendants ; and it is supposed that in one year there may be twenty...
Página 37 - ... and what is most remarkable, and without parallel, the sexual intercourse of one original pair serves for all the generations which proceed (mm the female for a whole succeeding year. Reaumur has proved that in five generations one Aphis may be the progenitor of 5,904,900,000 (billions) descendants; and it is supposed that in one year there may be 20 generations...
Página 42 - an animal producing an offspring, which at no time resembles its parent, but which, on the other hand, itself brings forth a progeny, which returns in its form and nature to the parent animal, so that the maternal animal does not meet with its resemblance in its own brood, but in its descendants of the second, third, or fourth degree or generation ; and this always takes place in the different animals which exhibit the phenomenon in a determinate generation, or with the intervention of a determinate...
Página 69 - ... are continued, — this doctrine, I say, is repeated in full in this author's work on Parthenogenesis, and I will here quote one sentence, not only in illustration of this, but to show how different his own observations on the development of these animals are from mine, just described. He says : " One sees such portion of the germ-mass taken into the semi-transparent body of the embryo Aphis, like the remnant of the yolk in the chick. I at first thought it was about to be enclosed in the alimentary...
Página 45 - Owen does not recognize any physiological difference between a bud and an ovum. This is clear from what he remarks in the first quotation ; but in his work on Parthenogenesis he has said so in as many words. " The growth by cell-multiplication producing a bud, instead of being altogether distinct from the growth by cell-multiplication in an egg, is essentially the same kind of growth or developmental process.
Página 29 - One conjunction of the sexes suffices for the impregnation of all the females that in a succession of generations spring from that union." In support of the reasonableness of this hypothesis, they quote several instances which they regard as of analogous character ; thus, they say in regard to the hive-bee, that " a single intercourse with the male fertilizes all the eggs that are laid for the space of two years.
Página 5 - Not all the progeny of the primary impregnated germcell are required for the formation of the body in all animals : certain of the derivative germ-cells may remain unchanged and become included in that body which has been composed of their metamorphosed and diversely combined or confluent brethren : so included, any derivative germ-cell or the nucleus of such may commence and repeat the same processes...
Página 5 - not all the progeny of the primary germ-cell are required for the formation of the body in all animals : certain of the derivative germ-cells may remain unchanged, and become included in that body which has been composed of their metamorphosed and diversely combined or confluent brethren : so included, any derivative germ-cell, or the nucleus of such, may commence and repeat the same processes of growth by imbibition, and of propagation by spontaneous fission, as those to which itself owed its origin.