The Origin of Species by Means of Natural Selection; Or, the Preservation of Favored Races in the Struggle for Life ...A.L. Burt, 1890 - 538페이지 |
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... VARIABILITY . WHEN we compare the individuals of the same variety or sub - variety of our older cultivated plants and animals , one of the first points which strikes us is , that they gen- erally differ more from each other than do the ...
... VARIABILITY . WHEN we compare the individuals of the same variety or sub - variety of our older cultivated plants and animals , one of the first points which strikes us is , that they gen- erally differ more from each other than do the ...
37 페이지
... variability , both by acting directly on the organization , and indirectly by affecting the reproductive system . It is not probable that variability is an inherent and necessary contingent , under all circum- stances . The greater or ...
... variability , both by acting directly on the organization , and indirectly by affecting the reproductive system . It is not probable that variability is an inherent and necessary contingent , under all circum- stances . The greater or ...
144 페이지
... variability in the parts undergoing modi- fication may always be expected . Now let us turn to nature . When a part ... variability , which has continually been accumulated by natural selection for the benefit of the species . But as the ...
... variability in the parts undergoing modi- fication may always be expected . Now let us turn to nature . When a part ... variability , which has continually been accumulated by natural selection for the benefit of the species . But as 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 gilt top Glacial period gradations greater number groups of species habits Hence hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate 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 variability variations varieties vary whole widely different wings young