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 5
... fertility of species and the fertility of varieties when intercrossed ; and fourthly , the imperfection of the Geological Record . In the next chapter I shall consider the geological succession of organic beings throughout time ; in the ...
... fertility of species and the fertility of varieties when intercrossed ; and fourthly , the imperfection of the Geological Record . In the next chapter I shall consider the geological succession of organic beings throughout time ; in the ...
Página 9
... fertile eggs . Many exotic plants have pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding ...
... fertile eggs . Many exotic plants have pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding ...
Página 15
... fertility of varieties when crossed , ―a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as , only in most cases in a lesser degree than , do closely - allied species of ...
... fertility of varieties when crossed , ―a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as , only in most cases in a lesser degree than , do closely - allied species of ...
Página 24
... fertile . I can state this from my own observations , purposely made , on the most distinct breeds . Now , it is difficult , perhaps impossible , to bring forward one case of the hybrid offspring of two animals clearly distinct being ...
... fertile . I can state this from my own observations , purposely made , on the most distinct breeds . Now , it is difficult , perhaps impossible , to bring forward one case of the hybrid offspring of two animals clearly distinct being ...
Página 25
... fertile , inter se , seems to me rash in the extreme . From these several reasons , namely , the improbability of man having formerly got seven or eight supposed species of pigeons to breed freely under domestica- tion ; these supposed ...
... fertile , inter se , seems to me rash in the extreme . From these several reasons , namely , the improbability of man having formerly got seven or eight supposed species of pigeons to breed freely under domestica- tion ; these supposed ...
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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