The Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeCollier Books, 1962 - 512 páginas |
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Página 246
... marsupial form ; and if so , the mammary glands will have been at first developed within the marsupial sack . In the case of the fish ( Hippocampus ) the eggs are hatched , and the young are reared for a time , within a sack of this ...
... marsupial form ; and if so , the mammary glands will have been at first developed within the marsupial sack . In the case of the fish ( Hippocampus ) the eggs are hatched , and the young are reared for a time , within a sack of this ...
Página 259
... marsupial sack secreted a nutritious fluid ; and that these glands were improved in function through natural selection , and concentrated into a confined area , in which case they would have formed a mamma . There is no more difficulty ...
... marsupial sack secreted a nutritious fluid ; and that these glands were improved in function through natural selection , and concentrated into a confined area , in which case they would have formed a mamma . There is no more difficulty ...
Página 495
... Marsupial , which will naturally have been more or less intermediate in character with respect to all existing Marsupials ; or that both Rodents and Marsupials branched off from a common progenitor , and that both groups have since ...
... Marsupial , which will naturally have been more or less intermediate in character with respect to all existing Marsupials ; or that both Rodents and Marsupials branched off from a common progenitor , and that both groups have since ...
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Términos y frases comunes
adapted admit affinities allied species America analogous ancient animals appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour continent crossed crustaceans degree developed difficulty distinct species domestic doubt effects eggs embryo existing extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological Glacial period gradations greater number habits Hence hybrids important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner marsupial migration modified descendants natural selection naturalists nearly nest occasionally oceanic islands offspring organisation organs Origin of Species parent peculiar perfect pigeon pistil plants pollen present principle probably produced quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed swimbladder tend theory tion variability variations varieties vary whilst whole wings young