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 10
... species , exists , they must certainly be highly or perfectly fertile . With our domesticated animals , the various races when crossed together are quite fertile ; yet in many cases they ... distinct species . 10 [ CHAP . IX . HYBRIDISM .
... species , exists , they must certainly be highly or perfectly fertile . With our domesticated animals , the various races when crossed together are quite fertile ; yet in many cases they ... distinct species . 10 [ CHAP . IX . HYBRIDISM .
Página 11
Charles Darwin. forms must be regarded as good and distinct species . The same remarks may be extended to the two chief races of the pig . We must , therefore , either give up the belief of the universal sterility of species when crossed ...
Charles Darwin. forms must be regarded as good and distinct species . The same remarks may be extended to the two chief races of the pig . We must , therefore , either give up the belief of the universal sterility of species when crossed ...
Página 14
... species of Nicotiana have been more largely crossed than the species of almost any other genus ; but Gärtner found that N. acuminata , which is not a particularly distinct species , obstinately failed to fertilise , or to be fertilised ...
... species of Nicotiana have been more largely crossed than the species of almost any other genus ; but Gärtner found that N. acuminata , which is not a particularly distinct species , obstinately failed to fertilise , or to be fertilised ...
Página 16
... distinct species , are united , their fertility graduates from zero to perfect fertility , or even to fertility under certain conditions in excess ; that their fertility , besides being eminently susceptible to favourable and unfa ...
... distinct species , are united , their fertility graduates from zero to perfect fertility , or even to fertility under certain conditions in excess ; that their fertility , besides being eminently susceptible to favourable and unfa ...
Página 18
... distinct families ; and , on the other hand , closely allied species , and varieties of the same species , can usually , but not invariably , be grafted with ease . But this capacity , as in hybridisation , is by no means absolutely ...
... distinct families ; and , on the other hand , closely allied species , and varieties of the same species , can usually , but not invariably , be grafted with ease . But this capacity , as in hybridisation , is by no means absolutely ...
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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