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 2
... namely , the sterility of species when first crossed , and the sterility of the hybrids produced from them . Pure species have of course their organs of reproduc- tion in a perfect condition , yet when intercrossed they produce either ...
... namely , the sterility of species when first crossed , and the sterility of the hybrids produced from them . Pure species have of course their organs of reproduc- tion in a perfect condition , yet when intercrossed they produce either ...
Página 4
... namely Köl- reuter and Gärtner , arrived at diametrically opposite conclusions in regard to some of the very same forms . It is also most instructive to compare - but I have not space here to enter on details - the evidence advanced by ...
... namely Köl- reuter and Gärtner , arrived at diametrically opposite conclusions in regard to some of the very same forms . It is also most instructive to compare - but I have not space here to enter on details - the evidence advanced by ...
Página 5
... namely , by too close interbreeding . I have made so many experiments and collected so many facts , show- ing on the one hand that an occasional cross with a dis- tinct individual or variety increases the vigour and fer- tility of the ...
... namely , by too close interbreeding . I have made so many experiments and collected so many facts , show- ing on the one hand that an occasional cross with a dis- tinct individual or variety increases the vigour and fer- tility of the ...
Página 6
... namely , the Hon . and Rev. W. Herbert . He is as emphatic in his conclusion that some hybrids are perfectly fertile - as fertile as the pure parent - species - as are Kölreuter and Gärtner that some degree of sterility between distinct ...
... namely , the Hon . and Rev. W. Herbert . He is as emphatic in his conclusion that some hybrids are perfectly fertile - as fertile as the pure parent - species - as are Kölreuter and Gärtner that some degree of sterility between distinct ...
Página 7
... namely , that individual plants of certain species of Lobelia , Verbascum and Passiflora , can easily be fertilised by pollen from a distinct species , but not by pollen from the same plant , though this pollen can be proved to be ...
... namely , that individual plants of certain species of Lobelia , Verbascum and Passiflora , can easily be fertilised by pollen from a distinct species , but not by pollen from the same plant , though this pollen can be proved to be ...
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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