The Origin of Species by Means of Natural Selection: Or the Preservation of Favored Races in the Struggle for LifeD. Appleton, 1904 - 435 páginas |
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Página 120
... fertility is greatly diminished if these visits be prevented . Now , it is scarcely possible for insects to fly from flower to flower , and not to carry pollen from one to the other , to the great good of the plant . Insects act like a ...
... fertility is greatly diminished if these visits be prevented . Now , it is scarcely possible for insects to fly from flower to flower , and not to carry pollen from one to the other , to the great good of the plant . Insects act like a ...
Página 127
... fertility over the offspring from long - continued self - fertilisation , that they will have a better chance of surviving and propa- gating their kind ; and thus in the long run the influ- ence of crosses , even at rare intervals ...
... fertility over the offspring from long - continued self - fertilisation , that they will have a better chance of surviving and propa- gating their kind ; and thus in the long run the influ- ence of crosses , even at rare intervals ...
Página 175
... fertile ( a far severer test ) under them , may be used as an argument that a large proportion of other animals now in a state of nature could easily be brought to bear widely different climates . We must not , how- ever , push the ...
... fertile ( a far severer test ) under them , may be used as an argument that a large proportion of other animals now in a state of nature could easily be brought to bear widely different climates . We must not , how- ever , push the ...
Página 208
... fertility is unimpaired ? The two first heads will here be discussed ; some miscellaneous objections in the following chapter ; In- stinct and Hybridism in the two succeeding chapters . On the Absence or Rarity of Transitional Varieties ...
... fertility is unimpaired ? The two first heads will here be discussed ; some miscellaneous objections in the following chapter ; In- stinct and Hybridism in the two succeeding chapters . On the Absence or Rarity of Transitional Varieties ...
Página 234
... fertile females ; but this case will be treated of in the next chapter . The electric organs of fishes offer another case of special difficulty ; for it is impossible to conceive by what steps these wondrous organs have been produced ...
... fertile females ; but this case will be treated of in the next chapter . The electric organs of fishes offer another case of special difficulty ; for it is impossible to conceive by what steps these wondrous organs have been produced ...
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Términos y frases comunes
adapted affinities allied species America ancient appear Asa Gray beak become bees believe belonging birds breeds cause cells characters climate closely allied colour common continent crossed crustaceans degree developed difficulty distinct species domestic doubt effects eggs embryo existing extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids important individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living males mammals manner marsupials migration modified descendants natural selection naturalists nearly nest occasionally offspring organisation organs parent peculiar perfect pigeon pistil pollen present principle probably produced progenitor quadrupeds ranked remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed swimbladder tend theory tion trees variability variations varieties vary whilst whole wings young