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
... perfect condition , yet when intercrossed they produce either few or no offspring . Hybrids , on the other hand , have their reproductive organs functionally impotent , as may be clearly seen in the state of the male element in both ...
... perfect condition , yet when intercrossed they produce either few or no offspring . Hybrids , on the other hand , have their reproductive organs functionally impotent , as may be clearly seen in the state of the male element in both ...
Página 4
... perfect fertility ends and sterility begins . I think no better evidence of this can be required than that the two most ex- perienced observers who have ever lived , namely Köl- reuter and Gärtner , arrived at diametrically opposite ...
... perfect fertility ends and sterility begins . I think no better evidence of this can be required than that the two most ex- perienced observers who have ever lived , namely Köl- reuter and Gärtner , arrived at diametrically opposite ...
Página 6
... perfect or even more than commonly perfect fertility , in a first cross between two distinct species . This case of the Crinum leads me to refer to a singular fact , namely , that individual plants of certain. 6 [ CHAP . IX . HYBRIDISM .
... perfect or even more than commonly perfect fertility , in a first cross between two distinct species . This case of the Crinum leads me to refer to a singular fact , namely , that individual plants of certain. 6 [ CHAP . IX . HYBRIDISM .
Página 11
... 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 curious ways this gradation can be shown ; but. CHAP . IX . ] 11 DEGREES OF STERILITY .
... 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 curious ways this gradation can be shown ; but. CHAP . IX . ] 11 DEGREES OF STERILITY .
Página 12
... perfect gradation in the number of seeds produced , up to nearly complete or even quite complete fertility ; and , as we have seen , in certain abnormal cases , even to an excess of fertility , beyond that which the plant's own pollen ...
... perfect gradation in the number of seeds produced , up to nearly complete or even quite complete fertility ; and , as we have seen , in certain abnormal cases , even to an excess of fertility , beyond that which the plant's own pollen ...
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