The Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeCollier Books, 1962 - 512 páginas |
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Página 122
... namely a1 and m1 . These two varieties will generally still be exposed to the same conditions which made their parents variable , and the tendency to variability is in itself hereditary ; consequently they will like- wise tend to vary ...
... namely a1 and m1 . These two varieties will generally still be exposed to the same conditions which made their parents variable , and the tendency to variability is in itself hereditary ; consequently they will like- wise tend to vary ...
Página 278
... namely , by too close interbreeding . I have made so many experiments and collected so many facts , showing on the one hand that an occasional cross with a distinct individual or variety increases the vigour and fertility of the ...
... namely , by too close interbreeding . I have made so many experiments and collected so many facts , showing on the one hand that an occasional cross with a distinct individual or variety increases the vigour and fertility of the ...
Página 300
... namely , that the yellow and white varieties when 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 ...
... namely , that the yellow and white varieties when 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 ...
Contenido
An Historical Sketch | 15 |
Introduction | 25 |
Variation Under Nature | 58 |
Derechos de autor | |
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Términos y frases comunes
accumulated adapted admit affinities allied species America analogous ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour common continent crossed crustaceans degree developed difficulty distinct species domestic doubt eggs embryo existing extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological Glacial period gradations greater number groups of species habits Hence hybrids important 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 pollen present principle probably produced progenitor quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed tend theory tion variability variations varieties vary whilst whole wings young