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 28
... characters be ever so slight , has had its wild prototype . At this rate there must have existed at least a score of species of wild cattle , as many sheep , and several goats in Europe alone , and several even within Great Britain ...
... characters be ever so slight , has had its wild prototype . At this rate there must have existed at least a score of species of wild cattle , as many sheep , and several goats in Europe alone , and several even within Great Britain ...
Página 32
... characters of the domestic breeds . Hence the supposed aboriginal stocks must either still exist in the countries where they were originally domesti- cated , and yet be unknown to ornithologists ; and this considering their size ...
... characters of the domestic breeds . Hence the supposed aboriginal stocks must either still exist in the countries where they were originally domesti- cated , and yet be unknown to ornithologists ; and this considering their size ...
Página 33
... characters . To give one instance out of several which I have observed : -I crossed some white fantails , which breed very true , with some black barbs - and it so happens that blue varieties of barbs are so rare that I never heard of ...
... characters . To give one instance out of several which I have observed : -I crossed some white fantails , which breed very true , with some black barbs - and it so happens that blue varieties of barbs are so rare that I never heard of ...
Página 34
... characters ( confined , as far as I have seen , to colour alone ) , if all the domestic breeds have descended from ... character derived from such cross will naturally become less and less , as in each succeeding generation there will be ...
... characters ( confined , as far as I have seen , to colour alone ) , if all the domestic breeds have descended from ... character derived from such cross will naturally become less and less , as in each succeeding generation there will be ...
Página 35
... characters in certain respects , as compared with all other Columbidæ , though so like in most other respects to the rock - pigeon ; the blue colour and various black marks occasionally appearing in all the breeds , both when kept pure ...
... characters in certain respects , as compared with all other Columbidæ , though so like in most other respects to the rock - pigeon ; the blue colour and various black marks occasionally appearing in all the breeds , both when kept pure ...
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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