The Origin of Species by Means of Natural Selection: Or, the Preservation of Favored Races in the Struggle for Life, 1권Hurst, 1890 - 501페이지 |
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140 페이지
... namely , that natural selection is continually trying to econo- mize every part of the organization . If under changed conditions of life a structure , before useful , becomes less useful , its diminution will be favored , for it will ...
... namely , that natural selection is continually trying to econo- mize every part of the organization . If under changed conditions of life a structure , before useful , becomes less useful , its diminution will be favored , for it will ...
175 페이지
... namely , flotation , may be converted into one for a widely different purpose , namely , respiration MODES OF TRANSITION 175.
... namely , flotation , may be converted into one for a widely different purpose , namely , respiration MODES OF TRANSITION 175.
280 페이지
... namely , by too close inter- breeding . I have made so many experiments and collected so many facts , showing on the one hand that an occasional cross with a distinct individual or variety increases the vigor and fertility of the ...
... namely , by too close inter- breeding . I have made so many experiments and collected so many facts , showing on the one hand that an occasional cross with a distinct individual or variety increases the vigor and fertility of the ...
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adapted admit affinities allied species America ancient appear Asa Gray beak become bees believe belonging birds breeds cause cells characters climate closely allied color continued crossed crustaceans degree developed difficulty distinct species domestic doubt effects eggs embryo existing extinct extremely facts favorable females fertility flowers formation forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate intervals kind lamellæ larvæ less living male mammals manner marsupials migration modified descendants natural selection naturalists nearly nest oceanic islands offspring organs parent peculiar perfect pigeons pistil pollen present principle probably produced quadrupeds ranked remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive suppose tend theory tion trees variability variations varieties vary whole widely different wings young