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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ix 페이지
... naturalists is that species , when intercrossed , have been specially en- dowed with sterility , in order to prevent their confusion . This view certainly seems at first highly probable , for species living together could hardly have ...
... naturalists is that species , when intercrossed , have been specially en- dowed with sterility , in order to prevent their confusion . This view certainly seems at first highly probable , for species living together could hardly have ...
34 페이지
... naturalists as species . For instance , the blue and red pimpernel , which are considered by most botanists as varieties , are said by Gärtner to be quite sterile when crossed , and he subsequently ranks them as undoubted species . If ...
... naturalists as species . For instance , the blue and red pimpernel , which are considered by most botanists as varieties , are said by Gärtner to be quite sterile when crossed , and he subsequently ranks them as undoubted species . If ...
70 페이지
... naturalists have no golden rule by which to distinguish species and varieties ; they grant some little variability to each species , but when they meet with a somewhat greater amount of difference between any two forms , they rank both ...
... naturalists have no golden rule by which to distinguish species and varieties ; they grant some little variability to each species , but when they meet with a somewhat greater amount of difference between any two forms , they rank both ...
71 페이지
... naturalists , as Agassiz and Pictet , maintain that all these tertiary species are specifically distinct , though the distinction is admitted to be very slight ; so that here , unless we believe that these eminent natu- ralists have ...
... naturalists , as Agassiz and Pictet , maintain that all these tertiary species are specifically distinct , though the distinction is admitted to be very slight ; so that here , unless we believe that these eminent natu- ralists have ...
118 페이지
... naturalists are not unanimous which forms ought to be ranked as highest : thus , some look at the selaceans or sharks , from their approach in some important points of struc- ture to reptiles , as the highest fish ; others look at the ...
... naturalists are not unanimous which forms ought to be ranked as highest : thus , some look at the selaceans or sharks , from their approach in some important points of struc- ture to reptiles , as the highest fish ; others look at the ...
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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