The Origin of Species by Means of Natural Selection,: Or the Preservation of Favoured Races in the Struggle for LifeAppleton, 1898 - 432 páginas |
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Página 2
... embryo are per- fect ; in the second case they are either not at all de- veloped , or are imperfectly developed . This distinc- tion is important , when the cause of the sterility , which is common to the two cases , has to be ...
... embryo are per- fect ; in the second case they are either not at all de- veloped , or are imperfectly developed . This distinc- tion is important , when the cause of the sterility , which is common to the two cases , has to be ...
Página 23
... embryo to be developed , as seems to have been the case with some of Thuret's experiments on Fuci . No explanation can be given of these facts , any more than why certain trees cannot be grafted on others . Lastly , an embryo may be ...
... embryo to be developed , as seems to have been the case with some of Thuret's experiments on Fuci . No explanation can be given of these facts , any more than why certain trees cannot be grafted on others . Lastly , an embryo may be ...
Página 24
... embryos within the eggs of silk moths which had not been fertilised , pass through their early stages of development and then perish like the embryos pro- duced by a cross between distinct species . Until becom- ing acquainted with ...
... embryos within the eggs of silk moths which had not been fertilised , pass through their early stages of development and then perish like the embryos pro- duced by a cross between distinct species . Until becom- ing acquainted with ...
Página 25
... embryo to be imper- fectly developed , rather than in the conditions to which it is subsequently exposed . In regard to the sterility of hybrids , in which the sexual elements are imperfectly developed , the case is somewhat different ...
... embryo to be imper- fectly developed , rather than in the conditions to which it is subsequently exposed . In regard to the sterility of hybrids , in which the sexual elements are imperfectly developed , the case is somewhat different ...
Página 45
... embryo . In the case of hybrids , it apparently depends on their whole organi- sation having been disturbed by being compounded from two distinct forms ; the sterility being closely . allied to that which so frequently affects pure ...
... embryo . In the case of hybrids , it apparently depends on their whole organi- sation having been disturbed by being compounded from two distinct forms ; the sterility being closely . allied to that which so frequently affects pure ...
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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