The Origin of Species by Means of Natural Selection,: Or the Preservation of Favoured Races in the Struggle for LifeAppleton, 1898 - 432페이지 |
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76개의 결과 중 1 - 5개
2 페이지
... produced from them . Pure species have of course their organs of reproduc- tion in a perfect condition , yet when intercrossed they produce either few or no offspring . Hybrids , on the other hand , have their reproductive organs ...
... produced from them . Pure species have of course their organs of reproduc- tion in a perfect condition , yet when intercrossed they produce either few or no offspring . Hybrids , on the other hand , have their reproductive organs ...
3 페이지
... produced by their hybrid offspring , with the average number produced by both pure parent - species in a state of nature . But causes of serious error here intervene : a plant , to be hybridised , must be castrated , and , what is often ...
... produced by their hybrid offspring , with the average number produced by both pure parent - species in a state of nature . But causes of serious error here intervene : a plant , to be hybridised , must be castrated , and , what is often ...
6 페이지
... produced a plant , which I never saw to occur in a case of its natural fecun- dation . " So that here we have perfect or even more than commonly perfect fertility , in a first cross between two distinct species . This case of the Crinum ...
... produced a plant , which I never saw to occur in a case of its natural fecun- dation . " So that here we have perfect or even more than commonly perfect fertility , in a first cross between two distinct species . This case of the Crinum ...
7 페이지
... produced four flowers ; three were fertilised by Herbert with their own pollen , and the fourth was subsequently fertilised by the pollen of a compound hybrid descended from three distinct species : the result was that the ovaries of ...
... produced four flowers ; three were fertilised by Herbert with their own pollen , and the fourth was subsequently fertilised by the pollen of a compound hybrid descended from three distinct species : the result was that the ovaries of ...
8 페이지
... produces itself as perfectly as if it had been a natural species from the mountains of Chili . " I have taken some ... produce no pollen , for he will find on their stigmas plenty of pollen brought from other flowers . men . In regard to ...
... produces itself as perfectly as if it had been a natural species from the mountains of Chili . " I have taken some ... produce no pollen , for he will find on their stigmas plenty of pollen brought from other flowers . men . In regard to ...
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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