The Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeJ. Murray, 1920 - 432페이지 |
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99개의 결과 중 1 - 5개
xv 페이지
... animals tend to vary in some degree , and , secondly , that agriculturists improve their domesticated animals by selection ; and then , he adds , but what is done in this latter case " by art , seems to be done with equal efficacy ...
... animals tend to vary in some degree , and , secondly , that agriculturists improve their domesticated animals by selection ; and then , he adds , but what is done in this latter case " by art , seems to be done with equal efficacy ...
3 페이지
... animals and of cultivated plants would offer the best chance of making out this obscure problem . Nor have I been disappointed ; in this and in all other perplexing cases I have invariably found that our knowledge , imperfect though it ...
... animals and of cultivated plants would offer the best chance of making out this obscure problem . Nor have I been disappointed ; in this and in all other perplexing cases I have invariably found that our knowledge , imperfect though it ...
5 페이지
... animals , one of the first points which strikes us is , that they generally differ more from each other than do the individuals of any one species or variety in a state of nature . And if we reflect on the vast diversity of the plants ...
... animals , one of the first points which strikes us is , that they generally differ more from each other than do the individuals of any one species or variety in a state of nature . And if we reflect on the vast diversity of the plants ...
7 페이지
... animals when reared under new or unnatural con- ditions . Many facts clearly show how eminently susceptible the reproductive system is to very slight changes in the surrounding conditions . Nothing is more easy than to tame an animal ...
... animals when reared under new or unnatural con- ditions . Many facts clearly show how eminently susceptible the reproductive system is to very slight changes in the surrounding conditions . Nothing is more easy than to tame an animal ...
8 페이지
... animals can be named which has not in some country drooping ears ; and the view which has been suggested that the drooping is due to disuse of the muscles of the ear , from the animals being seldom much alarmed , seems probable . Many ...
... animals can be named which has not in some country drooping ears ; and the view which has been suggested that the drooping is due to disuse of the muscles of the ear , from the animals being seldom much alarmed , seems probable . Many ...
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accumulated adapted admit affinities allied species America analogous ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour continued crossed crustaceans degree developed difficulty distinct species domestic animals doubt effects eggs embryo existing extinct extremely fact favourable female fertilised fertility flowers formation formerly forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number habits Hence hybrids important increase 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 occasionally oceanic islands offspring organisation organs parent peculiar perfect pigeon pistil pollen present preserved principle probably produced quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed tend theory tion variability variations varieties vary whilst whole wings young