On the Origin of Species by Means of Natural Selection: Or The Preservation of Favoured Races in the Struggle for LifeHumphrey Milford, Oxford University Press, 1923 - 454 páginas |
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Página 96
... existing species ; and if some of these many species become modified and improved , others will have to be improved in a corresponding degree or they will be exterminated . Each new form , also , as soon as it has been much im- proved ...
... existing species ; and if some of these many species become modified and improved , others will have to be improved in a corresponding degree or they will be exterminated . Each new form , also , as soon as it has been much im- proved ...
Página 113
... existing groups ; and we can understand this fact , for the extinct species lived at very ancient epochs when the branching lines of descent had diverged less . 14 to We shall I see no reason to limit the process of modification , as ...
... existing groups ; and we can understand this fact , for the extinct species lived at very ancient epochs when the branching lines of descent had diverged less . 14 to We shall I see no reason to limit the process of modification , as ...
Página 117
... existing species ; and those produced during each former year may represent the long succession of extinct species . At each period of growth all the growing twigs have tried to branch out on all sides , and to overtop and kill the ...
... existing species ; and those produced during each former year may represent the long succession of extinct species . At each period of growth all the growing twigs have tried to branch out on all sides , and to overtop and kill the ...
Página 146
... are crossed . Hence , though under nature it must generally he left doubtful , what cases are reversions to an anciently existing character , and what are new but analogous variations , yet we ought 146 ON THE ORIGIN OF SPECIES.
... are crossed . Hence , though under nature it must generally he left doubtful , what cases are reversions to an anciently existing character , and what are new but analogous variations , yet we ought 146 ON THE ORIGIN OF SPECIES.
Página 157
... existing in the inter- mediate zones . By changes in the form of the land and of climate , marine areas now continuous must often have existed within recent times in a far less continuous and uniform condition than at present . But I ...
... existing in the inter- mediate zones . By changes in the form of the land and of climate , marine areas now continuous must often have existed within recent times in a far less continuous and uniform condition than at present . But I ...
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Términos y frases comunes
accumulated adapted affinities allied species America amount analogous ancient appear Archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour common parent continuous crossed crustaceans degree difficulty distinct species divergence doubt embryo endemic Europe existing exterminated extinct extremely facts favourable fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hermaphrodites hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing land larvæ less living male mammals manner Marsupials migration modification modified descendants natural selection naturalists nearly nest oceanic islands offspring organisation perfect pigeons pistil plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary organs seeds sexual selection Silurian slight South America sterility structure struggle successive suppose swimbladder tend theory tion trees variability variation vary whole widely