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
... less fertile hybrids be artificially fertilised with hybrid pollen of the same kind , their fertility , notwithstanding the frequent ill effects from manipulation , sometimes decidedly increases , and goes on increasing . Now , in the ...
... less fertile hybrids be artificially fertilised with hybrid pollen of the same kind , their fertility , notwithstanding the frequent ill effects from manipulation , sometimes decidedly increases , and goes on increasing . Now , in the ...
Página 10
... less than eight hybrids ( grandchildren of the pure geese ) from one nest . In India , however , these cross - bred geese must be far more fertile ; for I am assured by two eminently capable judges , namely Mr. Blyth and Capt . Hutton ...
... less than eight hybrids ( grandchildren of the pure geese ) from one nest . In India , however , these cross - bred geese must be far more fertile ; for I am assured by two eminently capable judges , namely Mr. Blyth and Capt . Hutton ...
Página 14
... less than eight other species of Nicotiana . Many analogous facts could be 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 ...
... less than eight other species of Nicotiana . Many analogous facts could be 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 ...
Página 23
... less difficulty in effecting an union and in obtaining offspring apparently depends on several distinct causes . There must sometimes be a physical impossibility in the male element reaching the ovule , as would be the case with a plant ...
... less difficulty in effecting an union and in obtaining offspring apparently depends on several distinct causes . There must sometimes be a physical impossibility in the male element reaching the ovule , as would be the case with a plant ...
Página 25
... less sterile hybrids . Lastly , when organic beings are placed during several generations under conditions not natural to them , they are extremely liable to vary , which seems to. 28 CHAP . IX . ] OF FIRST CROSSES AND OF HYBRIDS . 25.
... less sterile hybrids . Lastly , when organic beings are placed during several generations under conditions not natural to them , they are extremely liable to vary , which seems to. 28 CHAP . IX . ] OF FIRST CROSSES AND OF HYBRIDS . 25.
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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