The Origin of Species by Means of Natural Selection,: Or the Preservation of Favoured Races in the Struggle for LifeAppleton, 1898 - 432페이지 |
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55개의 결과 중 1 - 5개
2 페이지
... structure , as far as the microscope reveals . In the first case the two sexual elements which go to form the embryo are per- fect ; in the second case they are either not at all de- veloped , or are imperfectly developed . This distinc ...
... structure , as far as the microscope reveals . In the first case the two sexual elements which go to form the embryo are per- fect ; in the second case they are either not at all de- veloped , or are imperfectly developed . This distinc ...
4 페이지
... structural differences . In regard to the sterility of hybrids in successive generations ; though Gärtner was enabled to rear some hybrids , carefully guarding them from a cross with either pure parent , for six or seven , and in one ...
... structural differences . In regard to the sterility of hybrids in successive generations ; though Gärtner was enabled to rear some hybrids , carefully guarding them from a cross with either pure parent , for six or seven , and in one ...
5 페이지
... structure or constitu- tion is common to both parents , this is often transmitted in an augmented degree to the offspring ; and both sexual elements in hybrid plants are already affected in some degree . But I believe that their ...
... structure or constitu- tion is common to both parents , this is often transmitted in an augmented degree to the offspring ; and both sexual elements in hybrid plants are already affected in some degree . But I believe that their ...
13 페이지
... structure and constitu- tion . Now the fertility of first crosses , and of the hybrids produced from them , is largely governed by their systematic affinity . This is clearly shown by hy- brids never having been raised between species ...
... structure and constitu- tion . Now the fertility of first crosses , and of the hybrids produced from them , is largely governed by their systematic affinity . This is clearly shown by hy- brids never having been raised between species ...
14 페이지
... ent of their systematic affinity , that is of any differ- ence in their structure or constitution , excepting in their reproductive systems . The diversity of the result in 14 LAWS GOVERNING THE STERILITY [ CHAP . IX .
... ent of their systematic affinity , that is of any differ- ence in their structure or constitution , excepting in their reproductive systems . The diversity of the result in 14 LAWS GOVERNING THE STERILITY [ CHAP . IX .
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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