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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54 페이지
Charles Darwin. genera and their recorded varieties which deserve notice . We have seen that there is no infallible criterion by which to distinguish species and well - marked varieties ; and when intermediate links have not been found ...
Charles Darwin. genera and their recorded varieties which deserve notice . We have seen that there is no infallible criterion by which to distinguish species and well - marked varieties ; and when intermediate links have not been found ...
55 페이지
... varieties are recorded , and these range over 7.7 provinces ; whereas , the species to which these varieties belong range over 14.3 provinces . So that the acknowledged varieties have nearly the same restricted average range , as have ...
... varieties are recorded , and these range over 7.7 provinces ; whereas , the species to which these varieties belong range over 14.3 provinces . So that the acknowledged varieties have nearly the same restricted average range , as have ...
70 페이지
... varieties of the same species , the struggle will generally be almost equally severe , and we sometimes see the contest soon decided : for instance , if several varieties of wheat be sown together and the mixed seed be resown , some of ...
... varieties of the same species , the struggle will generally be almost equally severe , and we sometimes see the contest soon decided : for instance , if several varieties of wheat be sown together and the mixed seed be resown , some of ...
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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