↑ 1 blocks not present in 1861 1866 1869 1872; present in 1859 1860 |
Although naturalists very properly demand a full explanation of every difficulty from those who believe in the mutability of species, on their own side they ignore the whole subject of the first appearance of species in what they consider reverent silence.
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→ fall away 1859 1860 1861 1866 1869 |
in favour of community of descent become fewer in number and less 1872 |
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→ groups. 1859 1860 1861 1866 1869 |
groups. Fossil remains sometimes tend to fill up very wide intervals between existing orders.
1872 |
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→ an embryonic 1859 1860 1861 1866 |
a very early 1869 1872 |
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→ class. 1859 1860 1861 1866 1869 |
great class or kingdom. 1872 |
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→ OMIT 1861 1866 1869 1872 |
germinal vesicles, their 1859 1860 |
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→ their liability to injurious influences. 1861 1866 1869 1872 |
reproduction. 1859 1860 |
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that innumerable beings within each great class have been created with plain, but deceptive, marks of descent from a single parent. ↑ |
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It may be asked how far I extend the doctrine of the modification of species. The question is difficult to answer, because the more distinct the forms are which we
consider, by so much the arguments
→fall away
in force. But some arguments of the greatest weight extend very far. All the members of whole classes
connected together by
of affinities, and all can be
on the same principle, in groups
to
→groups. Fossil remains sometimes tend to fill up very wide intervals between existing orders. Organs in a rudimentary condition plainly show that an early progenitor had the organ in a fully developed
and this in some
implies an enormous amount of modification in the descendants. Throughout whole classes various structures are formed on the same pattern, and at
→an embryonic
age the
closely resemble each other. Therefore I cannot doubt that the theory of descent with modification embraces all the members of the same
→class. I believe that animals
descended from at most only four or five progenitors, and plants from an equal or lesser number. |
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Analogy would lead me one step
namely, to the belief that all animals and plants
descended from some one prototype. But analogy may be a deceitful guide. Nevertheless all living things have much in
in their chemical composition, their
→OMIT
cellular structure,
their laws of
and
→their liability to injurious influences. We see this even in so trifling a
as that the same poison often similarly affects plants and animals; or that the poison secreted by the
produces monstrous growths on the wild
|