On the Origin of Species by Means of Natural Selection: Or The Preservation of Favoured Races in the Struggle for LifeHumphrey Milford, Oxford University Press, 1923 - 454 páginas |
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Página 52
... insects , that in large genera the amount of difference between the species is often exceedingly small . I have endeavoured to test this numerically by averages , and , as far as my imperfect results go , they confirm the view . I have ...
... insects , that in large genera the amount of difference between the species is often exceedingly small . I have endeavoured to test this numerically by averages , and , as far as my imperfect results go , they confirm the view . I have ...
Página 58
... insects or seeds , and are thus constantly destroying life ; or we forget how largely these songsters , or their eggs , or their nestlings , are destroyed by birds and beasts of prey ; we do not always bear in mind , that though food ...
... insects or seeds , and are thus constantly destroying life ; or we forget how largely these songsters , or their eggs , or their nestlings , are destroyed by birds and beasts of prey ; we do not always bear in mind , that though food ...
Página 63
... insects . If turf which has long been mown , and the case would be the same with turf closely browsed by quadrupeds , be let to grow , the more vigorous plants gradually kill the less vigorous , though fully grown , plants : thus out of ...
... insects . If turf which has long been mown , and the case would be the same with turf closely browsed by quadrupeds , be let to grow , the more vigorous plants gradually kill the less vigorous , though fully grown , plants : thus out of ...
Página 66
... insects must have been still greater , for six insectivorous birds were very common in the planta- tions , which were not to be seen on the heath ; and the heath was frequented by two or three distinct insectivorous birds . Here we see ...
... insects must have been still greater , for six insectivorous birds were very common in the planta- tions , which were not to be seen on the heath ; and the heath was frequented by two or three distinct insectivorous birds . Here we see ...
Página 67
... insects determine the existence of cattle . Perhaps Paraguay offers the most curious instance of this ; for here neither cattle nor horses nor dogs have ever run wild , though they swarm southward and northward in a feral state ; and ...
... insects determine the existence of cattle . Perhaps Paraguay offers the most curious instance of this ; for here neither cattle nor horses nor dogs have ever run wild , though they swarm southward and northward in a feral state ; and ...
Otras ediciones - Ver todas
Términos y frases comunes
accumulated adapted affinities allied species America amount analogous ancient appear Archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour common parent continuous crossed crustaceans degree difficulty distinct species divergence doubt embryo endemic Europe existing exterminated extinct extremely facts favourable fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hermaphrodites hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing land larvæ less living male mammals manner Marsupials migration modification modified descendants natural selection naturalists nearly nest oceanic islands offspring organisation perfect pigeons pistil plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary organs seeds sexual selection Silurian slight South America sterility structure struggle successive suppose swimbladder tend theory tion trees variability variation vary whole widely