On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeD. Appleton, 1909 - 430 páginas |
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Página 19
... seems pretty clear that organic beings must be ex- posed during several generations to the new conditions of life to cause any appreciable amount of variation ; and that when the organisation has once begun to vary , it generally ...
... seems pretty clear that organic beings must be ex- posed during several generations to the new conditions of life to cause any appreciable amount of variation ; and that when the organisation has once begun to vary , it generally ...
Página 22
... seems probable . There are many laws regulating variation , some few of which can be dimly seen , and will be hereafter briefly mentioned . I will here only allude to what may be called correlation of growth . Any change in the embryo ...
... seems probable . There are many laws regulating variation , some few of which can be dimly seen , and will be hereafter briefly mentioned . I will here only allude to what may be called correlation of growth . Any change in the embryo ...
Página 23
... seems to have become plastic , and tends to depart in some small degree from that of the parental type . [ Any variation which is not inherited is unimporta for us . But the number and diversity of inheritable deviations of structure ...
... seems to have become plastic , and tends to depart in some small degree from that of the parental type . [ Any variation which is not inherited is unimporta for us . But the number and diversity of inheritable deviations of structure ...
Página 25
... seems to me not improbable , that if we could succeed in naturalising , or were to cultivate , during many generations , the several races , for instance , of the cabbage , in very poor soil ( in which case , however , some effect would ...
... seems to me not improbable , that if we could succeed in naturalising , or were to cultivate , during many generations , the several races , for instance , of the cabbage , in very poor soil ( in which case , however , some effect would ...
Página 27
... true than seems to me to be the case , what does it show , but that some of our breeds originated there , four or five thousand years ago ? Since the recent discoveries of flint tools or VARIATION UNDER DOMESTICATION 27.
... true than seems to me to be the case , what does it show , but that some of our breeds originated there , four or five thousand years ago ? Since the recent discoveries of flint tools or VARIATION UNDER DOMESTICATION 27.
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Términos y frases comunes
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