On the Origin of Species by Means of Natural Selection: Or The Preservation of Favoured Races in the Struggle for LifeHumphrey Milford, Oxford University Press, 1923 - 454 páginas |
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Página 24
... distinct breed , the tendency to reversion to any character derived from such cross will naturally become less and less , as in each succeeding genera- tion there will be less of the foreign blood ; but when there has been no cross with ...
... distinct breed , the tendency to reversion to any character derived from such cross will naturally become less and less , as in each succeeding genera- tion there will be less of the foreign blood ; but when there has been no cross with ...
Página 26
... distinct breeds , that male and female pigeons can be easily mated for life ; and thus different breeds can be kept together in the same aviary . I have discussed the probable origin of domestic pigeons at some , yet quite insufficient ...
... distinct breeds , that male and female pigeons can be easily mated for life ; and thus different breeds can be kept together in the same aviary . I have discussed the probable origin of domestic pigeons at some , yet quite insufficient ...
Página 33
... distinct strains . The two flocks of Leicester sheep kept by Mr. Buckley and Mr. Burgess , as Mr. Youatt re- marks , ' have been purely bred from the original stock of Mr. Bakewell for upwards of fifty years . There is not a suspicion ...
... distinct strains . The two flocks of Leicester sheep kept by Mr. Buckley and Mr. Burgess , as Mr. Youatt re- marks , ' have been purely bred from the original stock of Mr. Bakewell for upwards of fifty years . There is not a suspicion ...
Página 34
... distinct to be ranked at their first appearance as distinct varieties , and whether or not two or more species or races have become blended together by crossing , may plainly be recognised in the increased size and beauty which we now ...
... distinct to be ranked at their first appearance as distinct varieties , and whether or not two or more species or races have become blended together by crossing , may plainly be recognised in the increased size and beauty which we now ...
Página 36
... distinct breeds , in which as many as seventeen tail - feathers have been counted . Perhaps the first pouter - pigeon did not inflate its crop much more than the turbit now does the upper part of its oesophagus , — -a habit which is ...
... distinct breeds , in which as many as seventeen tail - feathers have been counted . Perhaps the first pouter - pigeon did not inflate its crop much more than the turbit now does the upper part of its oesophagus , — -a habit which is ...
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Términos y frases comunes
accumulated adapted affinities allied species America amount analogous ancient appear Archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour common parent continuous crossed crustaceans degree difficulty distinct species divergence doubt embryo endemic Europe existing exterminated extinct extremely facts favourable fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hermaphrodites hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing land larvæ less living male mammals manner Marsupials migration modification modified descendants natural selection naturalists nearly nest oceanic islands offspring organisation perfect pigeons pistil plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary organs seeds sexual selection Silurian slight South America sterility structure struggle successive suppose swimbladder tend theory tion trees variability variation vary whole widely