The Origin of Species by Means of Natural Selection: Or the Preservation of Favored Races in the Struggle for LifeD. Appleton, 1904 - 435 páginas |
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Página 31
... perfect series ; so we can in some other cases , but not with all the breeds . Thirdly , those characters which are mainly distinctive of each breed are in each eminently variable , for instance the wattle and length of beak of the ...
... perfect series ; so we can in some other cases , but not with all the breeds . Thirdly , those characters which are mainly distinctive of each breed are in each eminently variable , for instance the wattle and length of beak of the ...
Página 35
... perfect and as useful as we now see them ; indeed , in many cases , we know that this has not been their history . The key is man's power of accumulative selection : nature gives successive varia- · tions ; man adds them up in certain ...
... perfect and as useful as we now see them ; indeed , in many cases , we know that this has not been their history . The key is man's power of accumulative selection : nature gives successive varia- · tions ; man adds them up in certain ...
Página 36
... perfect in itself , and then had given it existence . " In Saxony the im- portance of the principle of selection in regard to merino sheep is so fully recognised , that men follow it as a trade : the sheep are placed on a table and are ...
... perfect in itself , and then had given it existence . " In Saxony the im- portance of the principle of selection in regard to merino sheep is so fully recognised , that men follow it as a trade : the sheep are placed on a table and are ...
Página 52
... perfect , as that a complex machine should have been invented by man in a perfect state . Under domestication monstrosities sometimes occur which resemble normal structures in widely different animals . Thus pigs have occasionally been ...
... perfect , as that a complex machine should have been invented by man in a perfect state . Under domestication monstrosities sometimes occur which resemble normal structures in widely different animals . Thus pigs have occasionally been ...
Página 118
... perfect manner , by the continued preservation of all the individuals which presented slight deviations of struc- ture mutually favourable to each other . I am well aware that this doctrine of natural selec- tion , exemplified in the ...
... perfect manner , by the continued preservation of all the individuals which presented slight deviations of struc- ture mutually favourable to each other . I am well aware that this doctrine of natural selec- tion , exemplified in the ...
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Términos y frases comunes
adapted affinities allied species America ancient appear Asa Gray 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 effects eggs embryo existing extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological geological period 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 males mammals manner marsupials migration modified descendants natural selection naturalists nearly nest occasionally offspring organisation organs parent peculiar perfect pigeon pistil pollen present principle probably produced progenitor quadrupeds ranked remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed swimbladder tend theory tion trees variability variations varieties vary whilst whole wings young