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 249
... hybrids . Our chief object will be to see sterility of first whether or not these laws indicate that species have been specially crosses and of hybrids endowed with this quality , in order to prevent their crossing and blending together ...
... hybrids . Our chief object will be to see sterility of first whether or not these laws indicate that species have been specially crosses and of hybrids endowed with this quality , in order to prevent their crossing and blending together ...
Página 258
... hybrids . On the other hand , one species in a group will sometimes resist great changes of conditions with unimpaired fertility ; and certain species in a group will produce unusually fertile hybrids . No one can tell , till he tries ...
... hybrids . On the other hand , one species in a group will sometimes resist great changes of conditions with unimpaired fertility ; and certain species in a group will produce unusually fertile hybrids . No one can tell , till he tries ...
Página 268
... hybrids in the first generation are descended from species ( excluding those long - cultivated ) which have not had their reproductive systems in any way affected , and they are not variable ; but hybrids themselves have their ...
... hybrids in the first generation are descended from species ( excluding those long - cultivated ) which have not had their reproductive systems in any way affected , and they are not variable ; but hybrids themselves have their ...
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