On the Origin of Species by Means of Natural Selection, Or, The Preservation of Favoured Races in the Struggle for LifeAppleton, 1898 |
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Página 11
... fertility , both of first crosses and of hybrids , graduates from zero to perfect fertility . It is surprising in how many curious ways this gradation can be shown ; but CHAP . IX . ] 11 DEGREES OF STERILITY .
... fertility , both of first crosses and of hybrids , graduates from zero to perfect fertility . It is surprising in how many curious ways this gradation can be shown ; but CHAP . IX . ] 11 DEGREES OF STERILITY .
Página 12
... fertility , the pollen of different spe- cies applied to the stigma of some one species of the same genus , yields a perfect gradation in the number of seeds produced , up to nearly complete or even quite complete fertility ; and , as ...
... fertility , the pollen of different spe- cies applied to the stigma of some one species of the same genus , yields a perfect gradation in the number of seeds produced , up to nearly complete or even quite complete fertility ; and , as ...
Página 13
... fertility , both of first crosses and of hybrids , is more easily affected by unfavourable conditions , than is that of pure species . But the fertility of first crosses is likewise innately variable ; for it is not always the same in ...
... fertility , both of first crosses and of hybrids , is more easily affected by unfavourable conditions , than is that of pure species . But the fertility of first crosses is likewise innately variable ; for it is not always the same in ...
Página 15
... fertile ; but Kölreuter tried more than two hun- dred times , during eight following years , to fertilise reciprocally M ... fertility in a small , and oc- casionally in a high degree . Several other singular rules could be given from ...
... fertile ; but Kölreuter tried more than two hun- dred times , during eight following years , to fertilise reciprocally M ... fertility in a small , and oc- casionally in a high degree . Several other singular rules could be given from ...
Página 16
... fertility . These facts show how completely the fertility of a hybrid may be independent of its external resemblance to either pure parent . Considering the several rules now given , which govern the fertility of first causes and of ...
... fertility . These facts show how completely the fertility of a hybrid may be independent of its external resemblance to either pure parent . Considering the several rules now given , which govern the fertility of first causes and of ...
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admit affinity allied species ancient animals appear Archipelago arctic areas become believe birds Cambrian changes characters cies classification climate closely allied common progenitor continent crustaceans degree deposited difficulty distant distinct species domestic doubt embryo eral Europe existing extinct fact faunas fertilised fertility flowers formations formerly forms fossil fresh-water Fritz Müller Gärtner genera genus geological period geological record Glacial period groups of species habits hybrids hybrids produced important individuals inhabitants inherited insects instance intermediate intervals land larvæ less living mammals manner marine Marsupials migration modified descendants mongrels mountains natural selection naturalists nearly occur oceanic islands offspring organisation parent parent-form peculiar perfect pistil plants pollen present probably produced quadrupeds reciprocal crosses regions remains remarked reproductive resemblance rocks rudimentary organs sediment seeds Silurian South America stage stamens sterility structure successive suppose terrestrial tertiary theory tion variations varieties whilst widely different wings