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 12
... given . When pollen from a plant of one family is placed on the stigma of a plant of a distinct family , it exerts no more influence than so much inorganic dust . From this absolute zero of fertility , the pollen of different spe- cies ...
... given . When pollen from a plant of one family is placed on the stigma of a plant of a distinct family , it exerts no more influence than so much inorganic dust . From this absolute zero of fertility , the pollen of different spe- cies ...
Página 13
... given of very closely allied species which will not unite , or only with extreme difficulty ; and on the other hand of very dis- tinct species which unite with the utmost facility . In the same family there may be a genus , as Dianthus ...
... given of very closely allied species which will not unite , or only with extreme difficulty ; and on the other hand of very dis- tinct species which unite with the utmost facility . In the same family there may be a genus , as Dianthus ...
Página 14
... given . No one has been able to point out what kind or what amount of difference , in any recognisable character , is sufficient to prevent two species crossing . It can be shown that plants most widely different in habit and general ...
... given . No one has been able to point out what kind or what amount of difference , in any recognisable character , is sufficient to prevent two species crossing . It can be shown that plants most widely different in habit and general ...
Página 15
... given . Thuret has observed the same fact with certain sea - weeds or Fuci . Gärtner , moreover , found that this difference of facility in making recipro- cal crosses is extremely common in a lesser degree . He has observed it even ...
... given . Thuret has observed the same fact with certain sea - weeds or Fuci . Gärtner , moreover , found that this difference of facility in making recipro- cal crosses is extremely common in a lesser degree . He has observed it even ...
Página 16
... given , which govern the fertility of first causes and of hybrids , we see that when forms , which must be considered as good and distinct species , are united , their fertility graduates from zero to perfect fertility , or even to ...
... given , which govern the fertility of first causes and of hybrids , we see that when forms , which must be considered as good and distinct species , are united , their fertility graduates from zero to perfect fertility , or even to ...
Otras ediciones - Ver todas
The Origin of Species by Means of Natural Selection: Or the ..., Volumen2 Darwin Vista completa - 1889 |
On the Origin of Species by Means of Natural Selection Charles Darwin Sin vista previa disponible - 2016 |
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