Page - 170 - in The Origin of Species
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170 ORIGIN OF SPECIES
than that of quite useless or rudimentary organs being simi-
larly transmitted. A mere tendency to produce a rudiment
is indeed sometimes thus inherited.
As all the species of the same genus are supposed to be
descended from a common progenitor, it might be expected
that they would occasionally vary in an analogous manner;
so that the varieties of two or more species would resemble
each other, or that a variety of one species would resemble
in certain characters another and distinct species,—this other
species being, according to our view, only a well-marked and
permanent variety. But characters exclusively due to analo-
gous variation would probably be of an unimportant nature,
for the preservation of all functionally important characters
will have been determined through natural selection, in ac-
cordance with the different habits of the species. It might
further be expected that the species of the same genus would
occasionally exhibit reversions to long lost characters. As,
however, we do not know the common ancestor of any
natural group, we cannot distinguish between revisionary
and analogous characters. If, for instance, we did not know
that the parent rock-pigeon was not feather-footed or turn-
crowned, we could not have told, whether such characters in
our domestic breeds were reversions or only analogous varia-
tions; but we might have inferred that the blue colour was a
case of reversion from the number of the markings, which
are correlated with this tint, and which would not probably
have all appeared together from simple variation. More
especially we might have inferred this, from the blue colour
and the several marks so often appearing when differently
coloured breeds are crossed. Hence, although under nature it
must generally be left doubtful,what cases are reversions to
formerly existing characters, and what are new but analo-
gous variations, yet we ought, on our theory, sometimes to
find the varying offspring of a species assuming characters
which are already present in other members of the same
group. And this undoubtedly is the case.
The difficulty in distinguishing variable species is largely
due to the varieties mocking, as it were, other species of the
same genus. A considerable catalogue, also, could be given
of forms intermediate between two other forms, which them-
back to the
book The Origin of Species"
The Origin of Species
- Title
- The Origin of Species
- Author
- Charles Darwin
- Publisher
- P. F. Collier & Son
- Location
- New York
- Date
- 1909
- Language
- English
- License
- PD
- Size
- 10.5 x 16.4 cm
- Pages
- 568
- Keywords
- Evolutionstheorie, Evolution, Theory of Evolution, Naturwissenschaft, Natural Sciences
- Categories
- International
- Naturwissenschaften Biologie
Table of contents
- EDITOR'S INTRODUCTION 5
- AN HISTORICAL SKETCH of the Progress of Opinion on the Origin of Species 9
- INTRODUCTION 21
- Variation under Domestication 25
- Variation under Nature 58
- Struggle for Existence 76
- Natural Selection; or the Survival of the Fittest 93
- Laws of Variation 145
- Difficulties of the Theory 178
- Miscellaneous Objections to the Theory of Natural Selection 219
- Instinct 262
- Hybridism 298
- On the Imperfection of the Geological Record 333
- On the Geological Succession of Organic Beinss 364
- Geographical Distribution 395
- Geographical Distribution - continued 427
- Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs 450
- Recapitulation and Conclusion 499
- GLOSSARY 531
- INDEX 541