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 9
... occasionally appear in the young of the same litter , and in seedlings from the same seed - capsule . At long intervals of time , out of millions of individuals reared in the same coun- try and fed on nearly the same food , deviations ...
... occasionally appear in the young of the same litter , and in seedlings from the same seed - capsule . At long intervals of time , out of millions of individuals reared in the same coun- try and fed on nearly the same food , deviations ...
Página 17
... occasionally revert in some of their charac- ters to ancestral forms , it seems to me not improbable that if we could succeed in naturalising , or were to cultivate , during many generations , the several races , for instance , of the ...
... occasionally revert in some of their charac- ters to ancestral forms , it seems to me not improbable that if we could succeed in naturalising , or were to cultivate , during many generations , the several races , for instance , of the ...
Página 23
... occasional crosses , if aided by the careful selection of the individuals which present the desired character ; but to obtain a race intermediate between two quite distinct races , would be very difficult . Sir J. Sebright expressly ...
... occasional crosses , if aided by the careful selection of the individuals which present the desired character ; but to obtain a race intermediate between two quite distinct races , would be very difficult . Sir J. Sebright expressly ...
Página 30
... occasional re - appearance of the blue colour and various black marks in all the breeds , both when kept pure and when crossed ; -and lastly , the mongrel offspring being perfectly fertile ; -from these several reasons 30 [ CHAP . I ...
... occasional re - appearance of the blue colour and various black marks in all the breeds , both when kept pure and when crossed ; -and lastly , the mongrel offspring being perfectly fertile ; -from these several reasons 30 [ CHAP . I ...
Página 41
... occasional preservation of the best indi- viduals , whether or not sufficiently distinct to be ranked at their first appearance as distinct varieties , and whether or not two or more species or races have become blended together by ...
... occasional preservation of the best indi- viduals , whether or not sufficiently distinct to be ranked at their first appearance as distinct varieties , and whether or not two or more species or races have become blended together by ...
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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