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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38 페이지
... effected is proved by the enormous prices given for animals with a good pedigree ; and these have now been exported to almost every quarter of the world . The improvement is by no means generally due to crossing different breeds ; all ...
... effected is proved by the enormous prices given for animals with a good pedigree ; and these have now been exported to almost every quarter of the world . The improvement is by no means generally due to crossing different breeds ; all ...
41 페이지
... effected by crosses with the fox - hound ; but what concerns us is , that the change has been effected unconsciously and gradually , and yet so effectually , that , though the old Spanish pointer certainly came from Spain , Mr. Borrow ...
... effected by crosses with the fox - hound ; but what concerns us is , that the change has been effected unconsciously and gradually , and yet so effectually , that , though the old Spanish pointer certainly came from Spain , Mr. Borrow ...
46 페이지
... effected . I have seen it gravely remarked , that it was most fortunate that the strawberry began to vary just when gardeners began to attend closely to this plant . No doubt the strawberry had always varied since it was cultivated ...
... effected . I have seen it gravely remarked , that it was most fortunate that the strawberry began to vary just when gardeners began to attend closely to this plant . No doubt the strawberry had always varied since it was cultivated ...
50 페이지
... effected in the specific character ; but then we do not at present know by what steps , or for what good , a plant produces two kinds of flowers . With cultivated plants , in the few cases known of a variety habitually bearing flowers ...
... effected in the specific character ; but then we do not at present know by what steps , or for what good , a plant produces two kinds of flowers . With cultivated plants , in the few cases known of a variety habitually bearing flowers ...
51 페이지
... effected only by slow degrees ; yet quite recently Mr. Lubbock has shown a degree of variability in these main nerves in Coccus , which may almost be compared to the irregular branching of the stem of a tree . This philosophical ...
... effected only by slow degrees ; yet quite recently Mr. Lubbock has shown a degree of variability in these main nerves in Coccus , which may almost be compared to the irregular branching of the stem of a tree . This philosophical ...
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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