The Origin of Species by Means of Natural Selection: Or, The Preservation of Favored Races in the Struggle for Life, Volumen2D. Appleton, 1898 |
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Página 11
... extremely general result ; but that it cannot , under our present state of knowledge , be con- sidered as absolutely universal . Laws governing the Sterility of first Crosses and of Hybrids . We will now consider a little more in detail ...
... extremely general result ; but that it cannot , under our present state of knowledge , be con- sidered as absolutely universal . Laws governing the Sterility of first Crosses and of Hybrids . We will now consider a little more in detail ...
Página 14
... extremely close species a single hybrid . Even within the limits of the same genus , we meet with this same difference ; for instance , the many species of Nicotiana have been more largely crossed than the species of almost any other ...
... extremely close species a single hybrid . Even within the limits of the same genus , we meet with this same difference ; for instance , the many species of Nicotiana have been more largely crossed than the species of almost any other ...
Página 15
... extremely common in a lesser degree . He has observed it even between closely related forms ( as Matthiola annua and gilabra ) which many botanists rank only as varieties . It is also a remarkable fact , that hybrids raised from ...
... extremely common in a lesser degree . He has observed it even between closely related forms ( as Matthiola annua and gilabra ) which many botanists rank only as varieties . It is also a remarkable fact , that hybrids raised from ...
Página 17
... extremely different in degree , when various species are crossed , all of which we must suppose it would be equally im- portant to keep from blending together ? Why should the degree of sterility be innately variable in the in ...
... extremely different in degree , when various species are crossed , all of which we must suppose it would be equally im- portant to keep from blending together ? Why should the degree of sterility be innately variable in the in ...
Página 25
... extremely liable to have their reproductive systems seriously affected . This , in fact , is the great bar to the domestication of animals . Between the sterility thus superinduced and that of hybrids , there are many points of ...
... extremely liable to have their reproductive systems seriously affected . This , in fact , is the great bar to the domestication of animals . Between the sterility thus superinduced and that of hybrids , there are many points of ...
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Términos y frases comunes
admit affinity allied species ancient animals appear Archipelago arctic areas become believe belonging birds Cambrian changes characters cies classification climate closely allied continent crustaceans degree deposited difficulty distant distinct species domestic doubt embryo eral Europe existing extinct fact faunas fertilised fertility flowers formations formerly forms fossil fresh-water Fritz Müller Gärtner genera genus geological period geological record Glacial period groups of species habits hybrids hybrids produced important inhabitants inherited insects instance intermediate intervals land larvæ less living mammals manner marine Marsupials migration modified descendants mongrels mountains natural selection naturalists nearly occur oceanic islands offspring organisation palæontologists Palæozoic parent parent-form peculiar perfect pistil plants pollen present probably produced quadrupeds reciprocal crosses regions remains remarked reproductive resemblance rocks rudimentary organs seeds Silurian South America stage stamens sterility structure successive suppose terrestrial tertiary theory tion variations varieties whilst whole widely different wings