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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55 페이지
... ranges . This state- ment is indeed scarcely more than a truism , for , if a variety were found to have a wider range than that of its supposed parent species , their denominations would be reversed . But there is reason to believe that ...
... ranges . This state- ment is indeed scarcely more than a truism , for , if a variety were found to have a wider range than that of its supposed parent species , their denominations would be reversed . But there is reason to believe that ...
161 페이지
... range of any one species , depending as it does on the range of others , will tend to be sharply defined . Moreover , each species on the confines of its range , where it exists in les- sened numbers , will , during fluctuations in the ...
... range of any one species , depending as it does on the range of others , will tend to be sharply defined . Moreover , each species on the confines of its range , where it exists in les- sened numbers , will , during fluctuations in the ...
379 페이지
... range that their range is continuous . What a strange anomaly it would be if a directly opposite rule were to prevail when we go down one step lower in the series , namely , to the individuals of the same species , and these had not ...
... range that their range is continuous . What a strange anomaly it would be if a directly opposite rule were to prevail when we go down one step lower in the series , namely , to the individuals of the same species , and these had not ...
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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 divergence domestic doubt effects eggs embryo existing extinct extremely facts favorable 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 occasionally 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