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 3
... seeds , in order to show that there is any degree of sterility . He always compares the maximum number of seeds produced by two species when first crossed , and the maximum produced by their hybrid offspring , with the average number ...
... seeds , in order to show that there is any degree of sterility . He always compares the maximum number of seeds produced by two species when first crossed , and the maximum produced by their hybrid offspring , with the average number ...
Página 7
... seed , which vege- tated freely . " Mr. Herbert tried similar experiments during many years , and always with the same result . These cases serve to show on what slight and mysterious causes the lesser or greater fertility of a species ...
... seed , which vege- tated freely . " Mr. Herbert tried similar experiments during many years , and always with the same result . These cases serve to show on what slight and mysterious causes the lesser or greater fertility of a species ...
Página 8
... seeds as freely as it is possible to imagine . " Had hybrids when fairly treated , always gone on decreasing in fertility in each . successive generation , as Gärtner believed to be the case , the fact would have been notorious to ...
... seeds as freely as it is possible to imagine . " Had hybrids when fairly treated , always gone on decreasing in fertility in each . successive generation , as Gärtner believed to be the case , the fact would have been notorious to ...
Página 12
... 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 produces . So in hybrids themselves ...
... 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 produces . So in hybrids themselves ...
Página 13
... seed out of the same capsule and exposed to the same condi- tions . By the term systematic affinity is meant , the general resemblance between species in structure and constitu- tion . Now the fertility of first crosses , and of the ...
... seed out of the same capsule and exposed to the same condi- tions . By the term systematic affinity is meant , the general resemblance between species in structure and constitu- tion . Now the fertility of first crosses , and of the ...
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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