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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15 페이지
... pollen from one flower to the other , it is equally preposterous to account for the structure of this parasite , with its relations to several distinct organic beings , by the effects of external conditions , or of habit , or of the ...
... pollen from one flower to the other , it is equally preposterous to account for the structure of this parasite , with its relations to several distinct organic beings , by the effects of external conditions , or of habit , or of the ...
20 페이지
... pollen utterly worthless , in the same exact condition as in the most sterile 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 ...
... pollen utterly worthless , in the same exact condition as in the most sterile 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 ...
21 페이지
... pollen . But it is the opinion of most physiologists that there is no essential difference between a bud and an ovule in their earliest stages of formation ; so that , in fact , ' sports ' support the view , that variability may be ...
... pollen . But it is the opinion of most physiologists that there is no essential difference between a bud and an ovule in their earliest stages of formation ; so that , in fact , ' sports ' support the view , that variability may be ...
73 페이지
... pollen - masses and thus to fertilise them . I find from experiments that humble - bees are almost indispensable to the fertilisation of the heartsease ( Viola tricolor ) , for other bees do not visit this flower . I have also found ...
... pollen - masses and thus to fertilise them . I find from experiments that humble - bees are almost indispensable to the fertilisation of the heartsease ( Viola tricolor ) , for other bees do not visit this flower . I have also found ...
88 페이지
... pollen , and would certainly often transport the pollen from one flower to the stigma of another flower . The flowers of two distinct individuals of the same species would thus get crossed ; and the act of crossing , we have good reason ...
... pollen , and would certainly often transport the pollen from one flower to the stigma of another flower . The flowers of two distinct individuals of the same species would thus get crossed ; and the act of crossing , we have good reason ...
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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