On the Origin of Species by Means of Natural Selection, Or, The Preservation of Favoured Races in the Struggle for LifeAppleton, 1898 |
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Página 2
... tion in a 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 ...
... tion in a 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 ...
Página 5
... tion is common to both parents , this is often transmitted in an augmented degree to the offspring ; and both sexual elements in hybrid plants are already affected in some degree . But I believe that their fertility has been di ...
... tion is common to both parents , this is often transmitted in an augmented degree to the offspring ; and both sexual elements in hybrid plants are already affected in some degree . But I believe that their fertility has been di ...
Página 13
... tion . Now the fertility of first crosses , and of the hybrids produced from them , is largely governed by their systematic affinity . This is clearly shown by hy- brids never having been raised between species ranked by systematists in ...
... tion . Now the fertility of first crosses , and of the hybrids produced from them , is largely governed by their systematic affinity . This is clearly shown by hy- brids never having been raised between species ranked by systematists in ...
Página 27
... tion is offered why an organism , when placed under un- natural conditions , is rendered sterile . All that I have attempted to show is , that in two cases , in some respects allied , sterility is the common result , -in the one case ...
... tion is offered why an organism , when placed under un- natural conditions , is rendered sterile . All that I have attempted to show is , that in two cases , in some respects allied , sterility is the common result , -in the one case ...
Página 52
... tion of each formation , or even of each stratum . We can best gain some idea of past time by knowing the agencies at work , and learning how deeply the surface of the land has been denuded , and how much sediment has been deposited ...
... tion of each formation , or even of each stratum . We can best gain some idea of past time by knowing the agencies at work , and learning how deeply the surface of the land has been denuded , and how much sediment has been deposited ...
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Términos y frases comunes
admit affinity allied species ancient animals appear Archipelago arctic areas become believe birds Cambrian changes characters cies classification climate closely allied common progenitor 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 individuals 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 parent parent-form peculiar perfect pistil plants pollen present probably produced quadrupeds reciprocal crosses regions remains remarked reproductive resemblance rocks rudimentary organs sediment seeds Silurian South America stage stamens sterility structure successive suppose terrestrial tertiary theory tion variations varieties whilst widely different wings