The Origin of Species by Means of Natural Selection: Or, The Preservation of Favored Races in the Struggle for LifeP.F. Collier & son, 1902 - 356페이지 |
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12 페이지
... crossing of already existing forms , and much to use and disuse , that is , to the effects of habit . To this latter agency he seems to attribute all the beautiful adaptations in nature ; - such as the long neck of the giraffe for ...
... crossing of already existing forms , and much to use and disuse , that is , to the effects of habit . To this latter agency he seems to attribute all the beautiful adaptations in nature ; - such as the long neck of the giraffe for ...
34 페이지
... crossing of distinct species , and that which may be ob served with plants and animals when reared under new or unnatural conditions . Many facts clearly show how eminently susceptible the reproductive system is to very slight changes ...
... crossing of distinct species , and that which may be ob served with plants and animals when reared under new or unnatural conditions . Many facts clearly show how eminently susceptible the reproductive system is to very slight changes ...
42 페이지
... crossed - a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as do the closely - allied species of the same genus in a state of nature , but the differences in most cases ...
... crossed - a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as do the closely - allied species of the same genus in a state of nature , but the differences in most cases ...
45 페이지
... crossed them , and examined their skeletons , it appears to me almost certain that all are the descendants of the wild Indian fowl , Gallus bankiva ; and this is the conclusion of Mr. Blyth , and of others who have studied this bird in ...
... crossed them , and examined their skeletons , it appears to me almost certain that all are the descendants of the wild Indian fowl , Gallus bankiva ; and this is the conclusion of Mr. Blyth , and of others who have studied this bird in ...
46 페이지
... crossing of a few aboriginal species ; but by crossing we can only get forms in some degree intermediate between their parents ; and if we account for our several domestic races by this process , we must admit the former existence of ...
... crossing of a few aboriginal species ; but by crossing we can only get forms in some degree intermediate between their parents ; and if we account for our several domestic races by this process , we must admit the former existence of ...
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adapted admit affinities allied species America analogous ancient animals appear beak become bees believe belonging birds breeds cause cells characters climate closely allied color common continent crossed crustaceans degree developed difficulty distinct species domestic doubt eggs embryo existing extinct extremely facts favorable fertility flowers formation forms fossil Fritz Müller genera genus geological Glacial period gradations greater number groups of species habits Hence hybrids important individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner marsupial migration modification modified descendants natural selection naturalists nearly nest offspring organs ORIGIN OF SPECIES paleozoic parent peculiar perfect pigeon pistil plants pollen present principle probably produced progenitor quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed swimbladder theory tion trees variability variations varieties vary whole wings young