The Origin of Species by Means of Natural Selection,: Or the Preservation of Favoured Races in the Struggle for LifeJohn Murray, Albemarle Street., 1891 - 432 páginas |
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Página 7
... follows from the crossing of distinct species , and that which may be observed with plants and animals when reared under new or unnatural con- ditions . Many facts clearly show how eminently susceptible the reproductive system is to ...
... follows from the crossing of distinct species , and that which may be observed with plants and animals when reared under new or unnatural con- ditions . Many facts clearly show how eminently susceptible the reproductive system is to ...
Página 21
... - nised , that men follow it as a trade : the sheep are placed on a table and are studied , like a picture by a connoisseur ; this is done three times at intervals of months , and the sheep are. CHAP . I. ] 21 SELECTION BY MAN .
... - nised , that men follow it as a trade : the sheep are placed on a table and are studied , like a picture by a connoisseur ; this is done three times at intervals of months , and the sheep are. CHAP . I. ] 21 SELECTION BY MAN .
Página 34
... follow . We must , however , in many cases , decide by a majority of naturalists , for few well - marked and well - known varieties can be named which have not been ranked as species by at least some competent judges . That varieties of ...
... follow . We must , however , in many cases , decide by a majority of naturalists , for few well - marked and well - known varieties can be named which have not been ranked as species by at least some competent judges . That varieties of ...
Página 41
... genera . Both these results follow when another division is made , and when all the least genera , with from only one to four species , are altogether excluded from the tables . These. CHAP . II . ] SPECIES OF LARGER GENERA VARIABLE . 41.
... genera . Both these results follow when another division is made , and when all the least genera , with from only one to four species , are altogether excluded from the tables . These. CHAP . II . ] SPECIES OF LARGER GENERA VARIABLE . 41.
Página 45
... follow from the struggle for life . Owing to this struggle , variations , however slight and from whatever cause proceeding , if they be in any degree profitable to the individuals of a species , in their infinitely complex relations to ...
... follow from the struggle for life . Owing to this struggle , variations , however slight and from whatever cause proceeding , if they be in any degree profitable to the individuals of a species , in their infinitely complex relations to ...
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Términos y frases comunes
accumulated adapted admit affinities allied species America analogous ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour continued crossed crustaceans degree developed difficulty distinct species domestic animals doubt effects eggs embryo existing extinct extremely facts favourable female fertilised fertility flowers formation formerly forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number habits Hence hybrids important increase 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 occasionally occur oceanic islands offspring organisation organs parent peculiar perfect pigeon pistil pollen present preserved principle probably produced quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed tend theory tion variability variations varieties vary whilst whole wings young