The Origin of Species by Means of Natural Selection,: Or the Preservation of Favoured Races in the Struggle for LifeJohn Murray, Albemarle Street., 1891 - 432페이지 |
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7 페이지
... variability which follows from the crossing of distinct species , and that which may be observed with plants and animals when reared under new or unnatural con- ditions . Many facts clearly show how eminently susceptible the ...
... variability which follows from the crossing of distinct species , and that which may be observed with plants and animals when reared under new or unnatural con- ditions . Many facts clearly show how eminently susceptible the ...
12 페이지
... variability of the ass and goose , or the small power of endur- ance of warmth by the reindeer , or of cold by the common camel , prevented their domestication ? I cannot doubt that if other animals and plants , equal in number to our ...
... variability of the ass and goose , or the small power of endur- ance of warmth by the reindeer , or of cold by the common camel , prevented their domestication ? I cannot doubt that if other animals and plants , equal in number to our ...
21 페이지
... variability . We cannot suppose that all the breeds were suddenly produced as perfect and as useful as we now see them ; indeed , in many cases , we know that this has not been their history . The key is man's power of accumulative ...
... variability . We cannot suppose that all the breeds were suddenly produced as perfect and as useful as we now see them ; indeed , in many cases , we know that this has not been their history . The key is man's power of accumulative ...
27 페이지
... to man's power of selection . A high degree of variability is obviously favourable , as freely giving the materials for selection to work on ; not that mere individual differences are. CHAP . I. ] CIRCUMSTANCES FAVOURABLE TO SELECTION . 27.
... to man's power of selection . A high degree of variability is obviously favourable , as freely giving the materials for selection to work on ; not that mere individual differences are. CHAP . I. ] CIRCUMSTANCES FAVOURABLE TO SELECTION . 27.
29 페이지
... variability , both by acting directly on the organisation , and indirectly by affecting the reproductive system . It is not probable that variability is an inherent and necessary contingent , under all circumstances . The greater or ...
... variability , both by acting directly on the organisation , and indirectly by affecting the reproductive system . It is not probable that variability is an inherent and necessary contingent , under all circumstances . The greater or ...
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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 facts 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 occur 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