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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48 페이지
... known species which present the greatest number of spontaneous varieties and sub - varieties . Thus Quercus robur has twenty - eight varieties , all of which , excepting six , are clustered round three sub - species , namely Q ...
... known species which present the greatest number of spontaneous varieties and sub - varieties . Thus Quercus robur has twenty - eight varieties , all of which , excepting six , are clustered round three sub - species , namely Q ...
251 페이지
... known occasionally to lay their eggs in other birds ' nests . Now let us suppose that the ancient progenitor of our ... known to us only in a single species , is useless , for we have hitherto had no facts to guide us . Until recently ...
... known occasionally to lay their eggs in other birds ' nests . Now let us suppose that the ancient progenitor of our ... known to us only in a single species , is useless , for we have hitherto had no facts to guide us . Until recently ...
337 페이지
... known from south of the equator ; and by running through Pictet's Palæontology it will be seen that very few species are known from several formations in Europe . Some few families of fish now have a confined range ; the teleostean ...
... known from south of the equator ; and by running through Pictet's Palæontology it will be seen that very few species are known from several formations in Europe . Some few families of fish now have a confined range ; the teleostean ...
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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