The Origin of Species by Means of Natural Selection,: Or the Preservation of Favoured Races in the Struggle for LifeAppleton, 1898 - 432 páginas |
Dentro del libro
Resultados 1-5 de 78
Página 17
Charles Darwin. that species have been endowed with sterility simply to prevent their becoming confounded in nature ? I think not . For why should the sterility be so extremely different in degree , when various species are crossed , all ...
Charles Darwin. that species have been endowed with sterility simply to prevent their becoming confounded in nature ? I think not . For why should the sterility be so extremely different in degree , when various species are crossed , all ...
Página 23
... had been fertilised ; and in the majority of the fertilised eggs , the embryos had either been partially developed and had then per- ished , or had become nearly mature , but the CHAP . IX . ] OF FIRST CROSSES AND OF HYBRIDS . 23.
... had been fertilised ; and in the majority of the fertilised eggs , the embryos had either been partially developed and had then per- ished , or had become nearly mature , but the CHAP . IX . ] OF FIRST CROSSES AND OF HYBRIDS . 23.
Página 24
Charles Darwin. ished , or had become nearly mature , but the young chickens had been unable to break through the shell . Of the chickens which were born , more than four - fifths died within the first few days , or at latest weeks ...
Charles Darwin. ished , or had become nearly mature , but the young chickens had been unable to break through the shell . Of the chickens which were born , more than four - fifths died within the first few days , or at latest weeks ...
Página 28
... become widely or specifically different , produce hybrids which are almost always in some degree sterile . I am fully persuaded that this double parallelism is by no means an accident or an illusion . He who is able to explain why the ...
... become widely or specifically different , produce hybrids which are almost always in some degree sterile . I am fully persuaded that this double parallelism is by no means an accident or an illusion . He who is able to explain why the ...
Página 35
... become perfectly fer- tile together . With plants , so far is cultivation from giving a tendency towards sterility between distinct species , that in several well - authenticated cases already alluded to , certain plants have been ...
... become perfectly fer- tile together . With plants , so far is cultivation from giving a tendency towards sterility between distinct species , that in several well - authenticated cases already alluded to , certain plants have been ...
Otras ediciones - Ver todas
Términos y frases comunes
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