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 5
... 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 offspring , and on the other hand that very close interbreeding lessens their vigour and ...
... 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 offspring , and on the other hand that very close interbreeding lessens their vigour and ...
Página 6
... fact of an increase of fertility in the successive genera- tions of artificially fertilised hybrids , in contrast with those spontaneously self - fertilised , may , as I believe , be accounted for by too close interbreeding having been ...
... fact of an increase of fertility in the successive genera- tions of artificially fertilised hybrids , in contrast with those spontaneously self - fertilised , may , as I believe , be accounted for by too close interbreeding having been ...
Página 7
... fact , 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 ...
... fact , 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 ...
Página 8
... fact would have been notorious to nursery- Horticulturists raise large beds of the same hy- brid , and such alone are fairly treated , for by insect agency the several individuals are allowed to cross freely with each other , and the ...
... fact would have been notorious to nursery- Horticulturists raise large beds of the same hy- brid , and such alone are fairly treated , for by insect agency the several individuals are allowed to cross freely with each other , and the ...
Página 10
... fact we must conclude either that the abo- riginal parent - species at first produced perfectly fertile hybrids , or that the hybrids subsequently reared under domestication became quite fertile . This latter alter- native , which was ...
... fact we must conclude either that the abo- riginal parent - species at first produced perfectly fertile hybrids , or that the hybrids subsequently reared under domestication became quite fertile . This latter alter- native , which was ...
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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