The Origin of Species by Means of Natural Selection: Or, The Preservation of Favored Races in the Struggle for Life, 2권D. Appleton, 1898 |
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27개의 결과 중 1 - 5개
2 페이지
... 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 ...
23 페이지
... 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 ...
24 페이지
... 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 ...
25 페이지
... 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 ...
45 페이지
... 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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admit affinity allied species ancient animals appear Archipelago arctic areas become believe belonging birds Cambrian changes characters cies classification climate closely allied 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 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 palæontologists Palæozoic parent parent-form peculiar perfect pistil plants pollen present probably produced quadrupeds reciprocal crosses regions remains remarked reproductive resemblance rocks rudimentary organs seeds Silurian South America stage stamens sterility structure successive suppose terrestrial tertiary theory tion variations varieties whilst whole widely different wings