On parthenogenesis, a discourse introductory to the Hunterian lects. on generation and development, 18491849 |
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Página 45
... aggregates of female gemmiparous individuals in the form of leaves and buds ; and these , by the light of zoological ... aggregate of cells in an envelope , the * " In the vegetable this power or mode of propagation arises from two ...
... aggregates of female gemmiparous individuals in the form of leaves and buds ; and these , by the light of zoological ... aggregate of cells in an envelope , the * " In the vegetable this power or mode of propagation arises from two ...
Página 46
... aggregate of cells in an envelope that falls into the anterior chamber of the locular uterus of the virgin Aphis : only in the plant the aggregate of cells is detached from an external surface , but in the animal from an internal ...
... aggregate of cells in an envelope that falls into the anterior chamber of the locular uterus of the virgin Aphis : only in the plant the aggregate of cells is detached from an external surface , but in the animal from an internal ...
Página 54
... aggregate of modifications of the primitive type , not the fundamental pattern - plant itself . My idea of such , from the analogy of the typical vertebra or vertebrate skeleton * , is attempted to be expressed by the more simple forms ...
... aggregate of modifications of the primitive type , not the fundamental pattern - plant itself . My idea of such , from the analogy of the typical vertebra or vertebrate skeleton * , is attempted to be expressed by the more simple forms ...
Página 56
... , as being respectively individual organisms , derives seeming sup- port from the fact that in each species of composite plants and animals the aggregate of individuals assumes a de- 6 6 6 6 finite or specific form , whence the 56.
... , as being respectively individual organisms , derives seeming sup- port from the fact that in each species of composite plants and animals the aggregate of individuals assumes a de- 6 6 6 6 finite or specific form , whence the 56.
Página 57
... aggregates , are grouped together in each species , in so constant and specific a form , as to be readily recognized ... aggregate of egg - capsules or larval cells just cited . If , however , it should still be felt that the explanation ...
... aggregates , are grouped together in each species , in so constant and specific a form , as to be readily recognized ... aggregate of egg - capsules or larval cells just cited . If , however , it should still be felt that the explanation ...
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On Parthenogenesis, a Discourse Introductory to the Hunterian Lects. on ... Richard Owen (sir ) Sin vista previa disponible - 2019 |
Términos y frases comunes
aggregate alternate analogy animal animalcule Annelides Aphides appendages 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 successive tion tissues trematode unchanged virgin viviparous wet-nurse yelk zoophyte
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Página 33 - ... 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 22 - Assuredly, there is more birth and death in the world than is dreamt of by the greater part of us; but it is so masked, and on the whole, so little to our purpose, that we fail to see it.
Página 56 - ... repeats the process ; and it may be again repeated in the same geometrical ratio until a number which figures only can indicate and language almost fails to express, is the result. The Aphides...
Página 41 - 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 25 - 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 1 - 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 30 - Alternation of Generations^ is the remarkable phenomenon of 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...
Página 21 - The whole peripheral stratum of the retained germ-mass in contact with the primary integument is transformed into a new integument. These germ-cells have increased and propagated at the expense of the aliment assimilated by the alimentary canal. The formation of the new integument and of the new feet proceeds connectedly and contemporaneously : but the new parts are not moulded upon the inner surface of the old ones. The plastic force has changed its course of operation. A hinder segment of the body...