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 8
... find on their stigmas plenty of pollen brought from other flowers . men . In regard to animals , much fewer experiments have been carefully tried than with plants . If our systematic arrangements can be trusted , that is , if the genera ...
... find on their stigmas plenty of pollen brought from other flowers . men . In regard to animals , much fewer experiments have been carefully tried than with plants . If our systematic arrangements can be trusted , that is , if the genera ...
Página 11
... find how generally the same rules apply to both king- doms . It has been already remarked , that the degree of fertility , both of first crosses and of hybrids , graduates from zero to perfect fertility . It is surprising in how many ...
... find how generally the same rules apply to both king- doms . It has been already remarked , that the degree of fertility , both of first crosses and of hybrids , graduates from zero to perfect fertility . It is surprising in how many ...
Página 21
... find the subject extraordinarily complex . After mature reflection it seems to me that this could not have been effected through natural selection . Take the case of any two species which , when crossed , produced few and sterile ...
... find the subject extraordinarily complex . After mature reflection it seems to me that this could not have been effected through natural selection . Take the case of any two species which , when crossed , produced few and sterile ...
Página 32
... find that they yielded only about one - fifth of the proper number of seeds , and that they behaved in all the other above specified respects as if they had been two distinct species . But to make the case sure , he would raise plants ...
... find that they yielded only about one - fifth of the proper number of seeds , and that they behaved in all the other above specified respects as if they had been two distinct species . But to make the case sure , he would raise plants ...
Página 33
... find , and this seems to me of especial importance , that two or three forms of the same species may exist and may differ in no respect whatever , either in structure or in constitution , relatively to external conditions , and yet be ...
... find , and this seems to me of especial importance , that two or three forms of the same species may exist and may differ in no respect whatever , either in structure or in constitution , relatively to external conditions , and yet 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