The Origin of Species by Means of Natural Selection: Or the Preservation of Favored Races in the Struggle for LifeD. Appleton, 1904 - 435 páginas |
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Página 57
... form as a variety of another , even when they are closely con- nected by intermediate links ; nor will the commonly- assumed hybrid nature of the intermediate forms always remove the difficulty . In very many cases , however , one form ...
... form as a variety of another , even when they are closely con- nected by intermediate links ; nor will the commonly- assumed hybrid nature of the intermediate forms always remove the difficulty . In very many cases , however , one form ...
Página 58
... forms ! Amongst animals which unite for each birth , and which are highly locomotive , doubtful forms , ranked by one . zoologist as a species and by another as a variety , can rarely be found within the same country , but are com- mon ...
... forms ! Amongst animals which unite for each birth , and which are highly locomotive , doubtful forms , ranked by one . zoologist as a species and by another as a variety , can rarely be found within the same country , but are com- mon ...
Página 59
... forms and sub - species ; but as they are distin- guished from each other by a greater amount of differ- ence than that between the local forms and sub - species , they are almost universally ranked by naturalists as true species ...
... forms and sub - species ; but as they are distin- guished from each other by a greater amount of differ- ence than that between the local forms and sub - species , they are almost universally ranked by naturalists as true species ...
Página 60
... forms ought to be called species and which varieties . Mr. Walsh ranks the forms which it may be supposed would freely intercross , as varieties ; and those which appear to have lost this power , as species . As the differences depend ...
... forms ought to be called species and which varieties . Mr. Walsh ranks the forms which it may be supposed would freely intercross , as varieties ; and those which appear to have lost this power , as species . As the differences depend ...
Página 61
... forms in the different areas , there is always a good chance that intermediate forms will be discovered which will link together the extreme states , and these are then degraded to the rank of varie- ties . Some few naturalists maintain ...
... forms in the different areas , there is always a good chance that intermediate forms will be discovered which will link together the extreme states , and these are then degraded to the rank of varie- ties . Some few naturalists maintain ...
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Términos y frases comunes
adapted affinities allied species America ancient appear Asa Gray beak become bees believe belonging birds breeds cause cells characters climate closely allied colour common continent crossed crustaceans degree developed difficulty distinct species domestic doubt effects eggs embryo existing extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids important individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living males mammals manner marsupials migration modified descendants natural selection naturalists nearly nest occasionally offspring organisation organs parent peculiar perfect pigeon pistil pollen present principle probably produced progenitor quadrupeds ranked remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed swimbladder tend theory tion trees variability variations varieties vary whilst whole wings young