On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeCassell, 1909 - 430 páginas |
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Página 52
... gradations , that naturalists do not like to rank them as distinct species , are in several respects the most important for us . We have every reason to believe that many of these doubtful and closely - allied forms have permanently ...
... gradations , that naturalists do not like to rank them as distinct species , are in several respects the most important for us . We have every reason to believe that many of these doubtful and closely - allied forms have permanently ...
Página 160
... gradations , do we not everywhere see innumerable transitional forms ? Why is not all nature in confusion , instead of the species being , as we see them , well defined ? Secondly , is it possible that an animal having , for instance ...
... gradations , do we not everywhere see innumerable transitional forms ? Why is not all nature in confusion , instead of the species being , as we see them , well defined ? Secondly , is it possible that an animal having , for instance ...
Página 163
... gradations , the range of any one species , depending as it does on the range of others , will tend to be sharply defined . Moreover , each species on the con- fines of its range , where it exists in lessened numbers , will , during ...
... gradations , the range of any one species , depending as it does on the range of others , will tend to be sharply defined . Moreover , each species on the con- fines of its range , where it exists in lessened numbers , will , during ...
Página 172
... gradations from a perfect and complex eye to one very imperfect and simple , each grade being useful to its possessor , can be shown to exist ; if further , the eye does vary ever so slightly , and the varia- tions be inherited , which ...
... gradations from a perfect and complex eye to one very imperfect and simple , each grade being useful to its possessor , can be shown to exist ; if further , the eye does vary ever so slightly , and the varia- tions be inherited , which ...
Página 175
... gradations of some kind . Numerous cases could be given amongst the lower animals of the same organ performing at the same time wholly distinct functions ; thus the alimentary canal respires , digests , and excretes in the larva of the ...
... gradations of some kind . Numerous cases could be given amongst the lower animals of the same organ performing at the same time wholly distinct functions ; thus the alimentary canal respires , digests , and excretes in the larva of the ...
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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