On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeJ. Murray, 1860 - 502 páginas "In considering the Origin of Species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which most justly excites our admiration. Naturalists continually refer to external conditions, such as climate, food, & c, as the only possible cause of variation. In one very limited sense, as we shall hereafter see, this may be true; but it is preposterous to attribute to mere external conditions, the structure, for instance, of the woodpecker, with its feet, tail, beak, and tongue, so admirably adapted to catch insects under the bark of trees. In the case of the misseltoe, which draws its nourishment from certain trees, which has seeds that must be transported by certain birds, and which has flowers with separate sexes absolutely requiring the agency of certain insects to bring pollen from one flower to the other, it is equally preposterous to account for the structure of this parasite, with its relations to several distinct organic beings, by the effects of external conditions, or of habit, or of the volition of the plant itself"--Introduction. (PsycINFO Database Record (c) 2012 APA, all rights reserved) |
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Página 52
... supposed that all varieties or incipient species necessarily attain the rank of species . They may whilst in this incipient state become extinct , or they may endure as varieties for very long periods , as has been shown to be the case ...
... supposed that all varieties or incipient species necessarily attain the rank of species . They may whilst in this incipient state become extinct , or they may endure as varieties for very long periods , as has been shown to be the case ...
Página 58
... supposed parent - species , their denominations ought to be reversed . But there is also reason to believe , that those species which are very closely allied to other species , and in so far resemble varieties , often have much ...
... supposed parent - species , their denominations ought to be reversed . But there is also reason to believe , that those species which are very closely allied to other species , and in so far resemble varieties , often have much ...
Página 82
... supposed to have undergone a change , and this would manifestly be favourable to natural selection , by giving a better chance of profitable variations occurring ; and unless profitable variations do occur , natural selection can do ...
... supposed to have undergone a change , and this would manifestly be favourable to natural selection , by giving a better chance of profitable variations occurring ; and unless profitable variations do occur , natural selection can do ...
Página 96
... supposed hermaphrodites , and of real hermaphrodites a large number pair ; that is , two indivi- duals regularly unite for reproduction , which is all that concerns us . But still there are many hermaphrodite animals which certainly do ...
... supposed hermaphrodites , and of real hermaphrodites a large number pair ; that is , two indivi- duals regularly unite for reproduction , which is all that concerns us . But still there are many hermaphrodite animals which certainly do ...
Página 98
... supposed that bees would thus produce a multitude of hybrids between distinct species ; for if you bring on the same brush a plant's own pollen and pollen from another species , the former will have such a prepotent effect , that it ...
... supposed that bees would thus produce a multitude of hybrids between distinct species ; for if you bring on the same brush a plant's own pollen and pollen from another species , the former will have such a prepotent effect , that it ...
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Términos y frases comunes
adapted affinities allied species America analogous ancient animals become bees believe birds breeds cause cells chapter characters cirripedes climate closely allied colour continuous crossed crustaceans degree difficulty distinct species divergence domestic doubt embryo Europe existing exterminated extinct extremely facts favourable Fcap fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period greater number groups of species habits Hence hermaphrodites History hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate land larvæ less living male mammals manner migration modification modified descendants natural selection naturalists nearly nest offspring perfect pigeons plants pollen Portrait Post 8vo present principle probably produced progenitor racter ranked reciprocal crosses remarked resemble rudimentary organs Second Edition seeds sexual selection Silurian slight South America sterility structure struggle successive supposed theory Third Edition tion variability variations varieties vary Vols widely Woodcuts