| → differs, more or less, from the same part in the parents. 1859 1860 1861 1866 |
| has varied. 1869 1872 |
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| ↑ 1 blocks not present in 1859 1860 1861 1866; present in 1869 1872 |
| Changed conditions generally induce mere fluctuating variability, but sometimes they cause direct and definite effects; and these may become strongly marked in the course of time, though we have not sufficient evidence on this head.
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centuries, species; and how exactly parallel is the case with that of the species of the horse-genus! For myself, I venture confidently to look back thousands on thousands of generations, and I see an animal striped like a zebra, but perhaps otherwise very differently constructed, the common parent of our domestic
or not it be descended from one or more wild
of the ass, the hemionus, quagga, and zebra. |
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| He who believes that each equine species was independently created, will, I presume, assert that each species has been created with a tendency to vary, both under nature and under domestication, in this particular manner, so as often to become striped like
species of the genus; and that each has been created with a strong tendency, when crossed with species inhabiting distant quarters of the world, to produce hybrids resembling in their stripes, not their own parents, but other species of the genus. To admit this view is, as it seems to me, to reject a real for an unreal, or at least for an unknown, cause. It makes the works of God a mere mockery and deception; I would almost as soon believe with the old and ignorant cosmogonists, that fossil shells had never lived, but had been created in stone so as to mock the shells
living on the sea-shore. |
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| Our ignorance of the laws of variation is profound. Not in one case out of a hundred can we pretend to assign any reason why this or that part
→differs, more or less, from the same part in the parents. But whenever we have the means of instituting a comparison, the same laws appear to have acted in producing the lesser differences between varieties of the same species, and the greater differences between species of the same genus. ↑
The external conditions of life, as
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