On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeEaston Press, 1976 - 470 páginas |
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Página 15
... crossed a barb with a spot , which is a white bird with a red tail and red spot on the forehead , and which notoriously breeds very true ; the mongrels were dusky and mottled . I then crossed one of the mongrel barb - fantails with a ...
... crossed a barb with a spot , which is a white bird with a red tail and red spot on the forehead , and which notoriously breeds very true ; the mongrels were dusky and mottled . I then crossed one of the mongrel barb - fantails with a ...
Página 243
... crossed , and likewise the fertility of their mongrel offspring , is , with reference to my theory , of equal importance with the sterility of species ; for it seems to make a broad and clear distinction between varieties and species ...
... crossed , and likewise the fertility of their mongrel offspring , is , with reference to my theory , of equal importance with the sterility of species ; for it seems to make a broad and clear distinction between varieties and species ...
Página 266
... crossed produce less seed than the similarly coloured varieties of the same species . Moreover , he asserts that , when yellow and white varieties of one species are crossed with yellow and white varieties of a distinct species , more ...
... crossed produce less seed than the similarly coloured varieties of the same species . Moreover , he asserts that , when yellow and white varieties of one species are crossed with yellow and white varieties of a distinct species , more ...
Contenido
VARIATION UNDER NATURE | 30 |
STRUGGLE FOR EXISTENCE | 45 |
NATURAL SELECTION | 59 |
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Términos y frases comunes
accumulated adapted admit affinities allied species America ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour common progenitor continuous crossed crustaceans degree developed difficulty distinct species divergence doubt effects eggs embryo existing exterminated extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological geological period gradations greater number groups of species habits Hence hybrids hybrids produced important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner marsupials migration modified descendants natural selection naturalists nearly nest occasionally offspring organisation organs Origin of Species parent peculiar perfect pigeons pistil plants pollen present preserved principle probably produced quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds slight South America stamens sterility structure struggle successive supposed swimbladder theory variability variations varieties vary whilst whole wings young