The Science-history of the Universe, Volumen5Francis Rolt-Wheeler Current Literature Publishing Company, 1909 |
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Términos y frases comunes
adaptations altho animals animals and plants appear argument from ignorance biologists biology birds body carbon dioxide carbonic acid cell-theory cells centrosome changes characters chemical chlorophyll chromatin chromosomes classification color complex cytoplasm Darwin distinction division dwarf earth egg-cell eggs embryo energy environment essential evidence fact female fishes function fundamental germ germ-cells Hence heredity higher important individual inheritance inorganic insects kind known Lamarck lifeless matter living matter living substance living things males mammals ment metabolism microscope mitosis modifications molecules natural selection naturalists nitrogen nucleus observed occur origin of species orthogenesis ovum oxygen physiology plants and animals present problems produced proteid protoplasm recognised reproduction resemblance result says Schleiden scientific seeds selection theory sexual sexual selection similar simple species-forming spontaneous starch structure struggle for existence theory of descent tion tissues to-day unicellular variations vegetable vertebrate vital phenomena
Pasajes populares
Página 183 - There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered by the progeny of a single pair.
Página 223 - I attribute the modification of species exclusively to natural selection, I may be permitted to remark that in the first edition of this work, and subsequently, I placed in a most conspicuous position — namely, at the close of the Introduction — the following words : " I am convinced that natural selection has been the main but not the exclusive means of modification.
Página 132 - There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.
Página 185 - ... geometrical tendency to increase must be checked by destruction at some period of life. Our familiarity with the larger domestic animals tends, I think, to mislead us: we see no great destruction falling on them...
Página 198 - ... useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his...
Página 199 - Seeing that individual differences of the same kind perpetually recur, this can hardly be considered as an unwarrantable assumption. But whether it is true, we can judge only by seeing how far the hypothesis accords with and explains the general phenomena of nature. On the other hand, the ordinary belief that the amount of possible variation is a strictly limited quantity, is likewise a simple assumption. Although Natural Selection can act only through and for the good of each being, yet characters...
Página 222 - ... variations ; aided in an important manner by the inherited effects of the use and disuse of parts ; and in an unimportant manner, that is in relation to adaptive structures, whether past or present, by the direct action of external conditions, and by variations which seem to us in our ignorance to arise spontaneously. It appears that I formerly underrated the frequency and value of these latter forms of variation, as leading to permanent modifications of structure independently of natural selection.
Página 132 - It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth...
Página 199 - It may metaphorically be said that natural selection is daily and hourly scrutinizing, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.
Página 24 - Scriblerus accounted for the operation of the meatjack by its inherent "meat-roasting quality," and scorned the " materialism " of those who explained the turning of the spit by a certain mechanism worked by the draught of the chimney. If...