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 13
... individuals which happen to have been chosen for the experiment . So it is with hybrids , for their degree of fertility is often found to differ greatly in the several individuals raised from seed out of the same capsule and exposed to ...
... individuals which happen to have been chosen for the experiment . So it is with hybrids , for their degree of fertility is often found to differ greatly in the several individuals raised from seed out of the same capsule and exposed to ...
Página 16
... individuals sometimes are born , which closely resemble one of their pure parents ; and these hybrids are almost always utterly sterile , even when the other hybrids raised from seed from the same capsule have a considerable degree of ...
... individuals sometimes are born , which closely resemble one of their pure parents ; and these hybrids are almost always utterly sterile , even when the other hybrids raised from seed from the same capsule have a considerable degree of ...
Página 18
... individuals of the same two species in crossing ; so Sageret believes this to be the case with different individuals of the same two spe- cies in being grafted together . As in reciprocal crosses 18 LAWS GOVERNING THE STERILITY [ CHAP . IX ...
... individuals of the same two species in crossing ; so Sageret believes this to be the case with different individuals of the same two spe- cies in being grafted together . As in reciprocal crosses 18 LAWS GOVERNING THE STERILITY [ CHAP . IX ...
Página 20
... individuals of one variety when crossed with those of another variety . For it would clearly be advantage- ous to two varieties or incipient species , if they could be kept from blending , on the same principle that , when man is ...
... individuals of one variety when crossed with those of another variety . For it would clearly be advantage- ous to two varieties or incipient species , if they could be kept from blending , on the same principle that , when man is ...
Página 21
... sterile offspring ; now , what is there which could favour the survival of those individuals which happened to be endowed in a slightly higher degree with mutual infertility CHAP . IX . ] OF FIRST CROSSES AND OF HYBRIDS . 21.
... sterile offspring ; now , what is there which could favour the survival of those individuals which happened to be endowed in a slightly higher degree with mutual infertility CHAP . IX . ] OF FIRST CROSSES AND OF HYBRIDS . 21.
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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