On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeCassell, 1909 - 430 páginas |
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Página 8
... considered - Indefinite multiplication of species - Summary .. 78 CHAPTER V LAWS OF VARIATION Effects of external conditions - Use and disuse , combined with natural selection ; organs of flight and of vision - Acclimatisa- tion ...
... considered - Indefinite multiplication of species - Summary .. 78 CHAPTER V LAWS OF VARIATION Effects of external conditions - Use and disuse , combined with natural selection ; organs of flight and of vision - Acclimatisa- tion ...
Página 42
... considered as un- consciously followed , in so far that the breeders could never have expected or even have wished to produce the result which , ensued - namely , the production of two distinct strains . ] The two flocks of Leicester ...
... considered as un- consciously followed , in so far that the breeders could never have expected or even have wished to produce the result which , ensued - namely , the production of two distinct strains . ] The two flocks of Leicester ...
Página 52
... good species , and by another as mere varieties . Mr. H. C. Watson , to whom I lie under deep obligation for assistance of all kinds , has marked for me 182 British plants , which are generally considered 52 VARIATION UNDER NATURE.
... good species , and by another as mere varieties . Mr. H. C. Watson , to whom I lie under deep obligation for assistance of all kinds , has marked for me 182 British plants , which are generally considered 52 VARIATION UNDER NATURE.
Página 53
... considered as varieties , but which have all been ranked by botanists as species ; and in making this list he has omitted many trifling varieties , but which nevertheless have been ranked by some botanists as species , and he has ...
... considered as varieties , but which have all been ranked by botanists as species ; and in making this list he has omitted many trifling varieties , but which nevertheless have been ranked by some botanists as species , and he has ...
Página 54
... considered by highly - competent judges as varieties , have so perfectly the character of species that they are ranked by other highly - competent judges as good and true species . But to discuss whether such slightly different forms ...
... considered by highly - competent judges as varieties , have so perfectly the character of species that they are ranked by other highly - competent judges as good and true species . But to discuss whether such slightly different forms ...
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Términos y frases comunes
accumulated adapted affinities allied species America analogous ancient animals appear archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour continuous crossed crustaceans degree difficulty distinct species divergence domestic doubt embryo endemic existing exterminated extinct extremely facts favourable fertilised fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids hybrids produced important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate larvæ laws less living males mammals manner migration modification modified descendants natural selection naturalists nearly nest occasionally offspring organic organisation origin of species perfect pigeons plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary seeds sexual sexual selection Silurian slight sometimes South America sterility structure struggle successive supposed swimbladder tend theory variability variations varieties vary whole widely