On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeD. Appleton, 1909 - 430페이지 |
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9 페이지
... hybrids - Sterility not a special endowment , but incidental on other differences - Causes of the sterility of first crosses and of hybrids - Parallelism between the effects of changed conditions of life and of crossing - Fertility of ...
... hybrids - Sterility not a special endowment , but incidental on other differences - Causes of the sterility of first crosses and of hybrids - Parallelism between the effects of changed conditions of life and of crossing - Fertility of ...
20 페이지
... hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding quite freely under con- finement ; and when , on the other hand , we see individuals , though taken young from a ...
... hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding quite freely under con- finement ; and when , on the other hand , we see individuals , though taken young from a ...
34 페이지
... hybrids or mongrels from between all the domestic breeds of pigeons are perfectly fertile . I can state this from my ... hybrid offspring of two animals clearly distinct being them- selves perfectly fertile . Some authors believe that ...
... hybrids or mongrels from between all the domestic breeds of pigeons are perfectly fertile . I can state this from my ... hybrid offspring of two animals clearly distinct being them- selves perfectly fertile . Some authors believe that ...
48 페이지
... hybrids and mongrels , and the frequent sterility of hybrids ; but the cases of plants not propagated by seed are of little importance to us , for their endurance is only temporary . Over all these causes of Change I am convinced that ...
... hybrids and mongrels , and the frequent sterility of hybrids ; but the cases of plants not propagated by seed are of little importance to us , for their endurance is only temporary . Over all these causes of Change I am convinced that ...
52 페이지
... hybrid nature of the intermediate links always remove the difficulty . In very many cases , however , one form is ranked as a variety of another , not because the intermediate links have actually been found , but because analogy leads ...
... hybrid nature of the intermediate links always remove the difficulty . In very many cases , however , one form is ranked as a variety of another , not because the intermediate links have actually been found , but because analogy leads ...
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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