On the Origin of Species by Means of Natural Selection, Or, The Preservation of Favoured Races in the Struggle for LifeAppleton, 1898 - 432 páginas |
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Página 25
... 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.
... 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.
Página 26
... vary , as every experimentalist has observed . Thus we see that when organic beings are placed under new and unnatural conditions , and when hybrids are produced by the unnatural crossing of two species , the reproductive system ...
... vary , as every experimentalist has observed . Thus we see that when organic beings are placed under new and unnatural conditions , and when hybrids are produced by the unnatural crossing of two species , the reproductive system ...
Página 35
... varying conditions to which domesticated animals and cultivated plants have been subjected , have had so little tendency towards modify- ing the reproductive system in a manner leading to mutual sterility , that we have good grounds for ...
... varying conditions to which domesticated animals and cultivated plants have been subjected , have had so little tendency towards modify- ing the reproductive system in a manner leading to mutual sterility , that we have good grounds for ...
Página 55
... varies from 600 to 3000 feet . Professor Ramsay has published an account of a down- throw in Anglesea of 2300 feet ; and he informs me that he fully believes that there is one in Merioneth- shire of 12,000 feet ; yet in these cases ...
... varies from 600 to 3000 feet . Professor Ramsay has published an account of a down- throw in Anglesea of 2300 feet ; and he informs me that he fully believes that there is one in Merioneth- shire of 12,000 feet ; yet in these cases ...
Página 63
... varies from 30 or 40 to 60 fathoms , a widely extended formation might be formed during a period of elevation , and yet not suffer exces- sively from denudation during its slow upheaval ; but the thickness of the formation could not be ...
... varies from 30 or 40 to 60 fathoms , a widely extended formation might be formed during a period of elevation , and yet not suffer exces- sively from denudation during its slow upheaval ; but the thickness of the formation could not be ...
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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