On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeEaston Press, 1976 - 470 páginas |
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Página 49
... produced , and be produced , and yet the average stock be fully kept up ; but if many eggs or young are destroyed , many must be produced , or the species will become extinct . It would suffice to keep up the full number of a tree ...
... produced , and be produced , and yet the average stock be fully kept up ; but if many eggs or young are destroyed , many must be produced , or the species will become extinct . It would suffice to keep up the full number of a tree ...
Página 249
... produced , and probably never would produce , even with the pollen of the pure parents , a single fertile seed : but in some of these cases a first trace of fertility may be detected , by the pollen of one of the pure parent - species ...
... produced , and probably never would produce , even with the pollen of the pure parents , a single fertile seed : but in some of these cases a first trace of fertility may be detected , by the pollen of one of the pure parent - species ...
Página 330
... produced : for , as has been explained , it is incredible that individuals identically the same should have been produced from parents specifically distinct . Single centres of We are thus brought to the question which has been largely ...
... produced : for , as has been explained , it is incredible that individuals identically the same should have been produced from parents specifically distinct . Single centres of We are thus brought to the question which has been largely ...
Contenido
VARIATION UNDER NATURE | 30 |
STRUGGLE FOR EXISTENCE | 45 |
NATURAL SELECTION | 59 |
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Términos y frases comunes
accumulated adapted admit affinities allied species America ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour common progenitor continuous crossed crustaceans degree developed difficulty distinct species divergence doubt effects eggs embryo existing exterminated extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological geological period gradations greater number groups of species habits Hence hybrids hybrids produced important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner marsupials migration modified descendants natural selection naturalists nearly nest occasionally offspring organisation organs Origin of Species parent peculiar perfect pigeons pistil plants pollen present preserved principle probably produced quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds slight South America stamens sterility structure struggle successive supposed swimbladder theory variability variations varieties vary whilst whole wings young