On the Origin of Species by Means of Natural Selection: Or The Preservation of Favoured Races in the Struggle for LifeHumphrey Milford, Oxford University Press, 1923 - 454 páginas |
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Página 221
... sterility of the hybrids pro- duced from them . Pure species have of course their organs of reproduc- tion in a ... sterility , which is common to the two cases , has to be considered . The distinction has probably been slurred over ...
... sterility of the hybrids pro- duced from them . Pure species have of course their organs of reproduc- tion in a ... sterility , which is common to the two cases , has to be considered . The distinction has probably been slurred over ...
Página 222
... sterility of various species when crossed is so different in degree and graduates away so insensibly , and , on the other hand , that the fertility of pure species is so easily affected by various circumstances , that for all practical ...
... sterility of various species when crossed is so different in degree and graduates away so insensibly , and , on the other hand , that the fertility of pure species is so easily affected by various circumstances , that for all practical ...
Página 223
... sterility nor fertility affords any clear distinction between species and varieties ; but that the evidence from this source graduates away , and is doubtful in the same degree as is the evidence derived from other constitutional and ...
... sterility nor fertility affords any clear distinction between species and varieties ; but that the evidence from this source graduates away , and is doubtful in the same degree as is the evidence derived from other constitutional and ...
Página 224
... sterility between distinct species is a universal law of nature . He experimentised on some of the very same species as did Gärtner . The differ- ence in their results may , I think , be in part accounted for by Herbert's great ...
... sterility between distinct species is a universal law of nature . He experimentised on some of the very same species as did Gärtner . The differ- ence in their results may , I think , be in part accounted for by Herbert's great ...
Página 227
... sterility in the hybrids should have gone on increasing . If we were to act thus , and pair brothers and sisters in the case of any pure animal , which from any cause had the least tendency to sterility , the breed would assuredly be ...
... sterility in the hybrids should have gone on increasing . If we were to act thus , and pair brothers and sisters in the case of any pure animal , which from any cause had the least tendency to sterility , the breed would assuredly be ...
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Términos y frases comunes
accumulated adapted affinities allied species America amount analogous ancient appear Archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour common parent continuous crossed crustaceans degree difficulty distinct species divergence doubt embryo endemic Europe existing exterminated extinct extremely facts favourable fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hermaphrodites hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing land larvæ less living male mammals manner Marsupials migration modification modified descendants natural selection naturalists nearly nest oceanic islands offspring organisation perfect pigeons pistil plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary organs seeds sexual selection Silurian slight South America sterility structure struggle successive suppose swimbladder tend theory tion trees variability variation vary whole widely