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
... seeds that must be transported by certain birds , and which has flowers with separate sexes absolutely re- quiring the agency of certain insects to bring pollen from one flower to the other , it is equally preposterous to account for ...
... seeds that must be transported by certain birds , and which has flowers with separate sexes absolutely re- quiring the agency of certain insects to bring pollen from one flower to the other , it is equally preposterous to account for ...
20 페이지
... seed ! In some few such cases , it has been discovered that very trifling changes , such as a little more or less water at some particular period of growth , will determine whether or not the plant sets a seed . I cannot here enter on ...
... seed ! In some few such cases , it has been discovered that very trifling changes , such as a little more or less water at some particular period of growth , will determine whether or not the plant sets a seed . I cannot here enter on ...
21 페이지
... seed . These sports are extremely rare under nature , but far from rare under cultivation ; and in this case we see that the treatment of the parent has affected a bud or offset , and not the ovules or pollen . But it is the opinion of ...
... seed . These sports are extremely rare under nature , but far from rare under cultivation ; and in this case we see that the treatment of the parent has affected a bud or offset , and not the ovules or pollen . But it is the opinion of ...
36 페이지
... seeds of the same tree . Innumerable other examples could be given . explanation , I think , is simple : from long - continued study they are strongly impressed with the differences between the several races ; and though they well know ...
... seeds of the same tree . Innumerable other examples could be given . explanation , I think , is simple : from long - continued study they are strongly impressed with the differences between the several races ; and though they well know ...
39 페이지
... seed - raisers do not pick out the best plants , but merely go over their seed- beds , and pull up the rogues , ' as they call the plants that deviate from the proper standard . With animals this kind of selection is , in fact , also ...
... seed - raisers do not pick out the best plants , but merely go over their seed- beds , and pull up the rogues , ' as they call the plants that deviate from the proper standard . With animals this kind of selection is , in fact , also ...
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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