The Origin of Species by Means of Natural Selection; Or, the Preservation of Favored Races in the Struggle for Life ...A.L. Burt, 1890 - 538페이지 |
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142 페이지
... developed , unless it be unusually developed in one species or in a few species in comparison with the same part in many closely allied species . Thus , the wing of the bat is a most abnormal structure in the class of mammals , but the ...
... developed , unless it be unusually developed in one species or in a few species in comparison with the same part in many closely allied species . Thus , the wing of the bat is a most abnormal structure in the class of mammals , but the ...
230 페이지
... developed from a common origin ; and as the movable lip of the cell serves as a protec- tion to the zooid , there is no difficulty in believing that all the gradations , by which the lip became converted first into the lower mandible of ...
... developed from a common origin ; and as the movable lip of the cell serves as a protec- tion to the zooid , there is no difficulty in believing that all the gradations , by which the lip became converted first into the lower mandible of ...
468 페이지
... developed and to secrete milk . So again in the udders in the genus Bos , there are normally four developed and two rudimentary teats ; but the latter in our domestic cows sometimes be- come well developed and yield milk . In regard to ...
... developed and to secrete milk . So again in the udders in the genus Bos , there are normally four developed and two rudimentary teats ; but the latter in our domestic cows sometimes be- come well developed and yield milk . In regard to ...
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adapted admit affinities allied species America ancient appear Asa Gray beak become bees believe belonging birds breeds cause cells characters climate closely allied color continued crossed crustaceans degree developed difficulty distinct species domestic doubt effects eggs embryo existing extinct extremely facts favorable females fertility flowers formation forms fossil Fritz Müller genera genus geological geological period gilt top Glacial period gradations greater number groups of species habits Hence hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner marsupials migration modified descendants natural selection naturalists nearly nest oceanic islands offspring organs parent peculiar perfect pigeons pistil pollen present principle probably produced quadrupeds ranked remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive suppose tend theory tion variability variations varieties vary whole widely different wings young