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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45 페이지
... observed by Mr. Walsh to present in their larval or mature state , or in both states , slight , though constant differences in color , size , or in the nature of their secretions . In some instances the males alone , in other instances ...
... observed by Mr. Walsh to present in their larval or mature state , or in both states , slight , though constant differences in color , size , or in the nature of their secretions . In some instances the males alone , in other instances ...
129 페이지
... observed the same fact ) that the anterior tarsi , or feet , of many male dung - feeding beetles are often broken off ; he examined seventeen speci- mens in his own collection , and not one had even a relic left . In the Onites apelles ...
... observed the same fact ) that the anterior tarsi , or feet , of many male dung - feeding beetles are often broken off ; he examined seventeen speci- mens in his own collection , and not one had even a relic left . In the Onites apelles ...
178 페이지
... observed by Matteucci , an analogous organ in the tail manifests but little electricity , even when the animal is greatly irritated ; so little that it can hardly be of any use for the above purposes . over , in the ray , besides the ...
... observed by Matteucci , an analogous organ in the tail manifests but little electricity , even when the animal is greatly irritated ; so little that it can hardly be of any use for the above purposes . over , in the ray , besides the ...
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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