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 8
... separated by any clear line of distinction from mere variations . But I am strongly inclined to suspect that the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected ...
... separated by any clear line of distinction from mere variations . But I am strongly inclined to suspect that the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected ...
Página 29
... separating some very distinct variety , and breeding from it , the principle would be so obvious as hardly to be worth notice ; but its importance consists in the great effect produced by the accumulation in one direction , during ...
... separating some very distinct variety , and breeding from it , the principle would be so obvious as hardly to be worth notice ; but its importance consists in the great effect produced by the accumulation in one direction , during ...
Página 45
... separated areas . How many of those birds and insects in North America and Europe , which differ very slightly from each other , have been ranked by one eminent naturalist as undoubted species , and by another as varieties , or , as ...
... separated areas . How many of those birds and insects in North America and Europe , which differ very slightly from each other , have been ranked by one eminent naturalist as undoubted species , and by another as varieties , or , as ...
Página 84
... separation of the sexes of plants , presently to be alluded to . Some holly - trees bear only male flowers , which have four stamens producing a rather small quantity of pollen , and a rudimentary pistil ; other holly - trees bear only ...
... separation of the sexes of plants , presently to be alluded to . Some holly - trees bear only male flowers , which have four stamens producing a rather small quantity of pollen , and a rudimentary pistil ; other holly - trees bear only ...
Página 85
... separation of the sexes would be effected . Let us now turn to the nectar - feeding insects in our imaginary case : we may suppose the plant of which we have been slowly increasing the nectar by continued selection , to be a common ...
... separation of the sexes would be effected . Let us now turn to the nectar - feeding insects in our imaginary case : we may suppose the plant of which we have been slowly increasing the nectar by continued selection , to be a common ...
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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