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 30
... present day are compared with drawings made only twenty or thirty years ago . When a race of plants is once pretty well established , the seed - raisers do not pick out the best plants , but merely go over their seed - beds , and pull ...
... present day are compared with drawings made only twenty or thirty years ago . When a race of plants is once pretty well established , the seed - raisers do not pick out the best plants , but merely go over their seed - beds , and pull ...
Página 32
... present time , eminent breeders try by methodical selection , with a distinct object in view , to make a new strain or sub - breed , superior to anything existing in the country . But , for our purpose , a kind of Selection , which may ...
... present time , eminent breeders try by methodical selection , with a distinct object in view , to make a new strain or sub - breed , superior to anything existing in the country . But , for our purpose , a kind of Selection , which may ...
Página 35
... present standard of usefulness to man , we can understand how it is that neither Australia , the Cape of Good Hope , nor any other region inhabited by quite uncivilised man , has afforded us a single plant worth culture . It is not that ...
... present standard of usefulness to man , we can understand how it is that neither Australia , the Cape of Good Hope , nor any other region inhabited by quite uncivilised man , has afforded us a single plant worth culture . It is not that ...
Página 43
... present an inordinate amount of variation ; and hardly two naturalists can agree which forms to rank as species and which as varieties . We may instance Rubus , Rosa , and Hieracium amongst plants , several genera of insects , and ...
... present an inordinate amount of variation ; and hardly two naturalists can agree which forms to rank as species and which as varieties . We may instance Rubus , Rosa , and Hieracium amongst plants , several genera of insects , and ...
Página 49
... present varieties ; and this might have been expected , as they become exposed to diverse physical conditions , and as they come into competition ( which , as we shall hereafter see , is a far more important circumstance ) with ...
... present varieties ; and this might have been expected , as they become exposed to diverse physical conditions , and as they come into competition ( which , as we shall hereafter see , is a far more important circumstance ) with ...
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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