Page - 162 - in The Origin of Species
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Text of the Page - 162 -
162 ORIGIN OF SPECIES
only one, as it illustrates the rule in its largest application.
The opercular valves of sessile cirripedes (rock barnacles)
are, in every sense of the word, very important structures,
and they differ extremely little even in distinct genera; but
in the several species of one genus, Pyrgoma, these valves
present a marvellous amount of diversification
; the homolo-
gous valves in the different species being sometimes wholly
Mnlike in shape; and the amount of variation in the indi-
viduals of the same species is so great, that it is no exag-
geration to state that the varieties of the same species differ
more from each other in the characters derived from these
important organs, than do the species belonging to other
distinct genera.
As with birds the individuals of the same species, inhabit-
ing the same coimtry, vary extremely little, I have particu-
larly attended to them; and the rule certainly seems to hold
good in this class. I cannot make out that it applies to plants,
and this would have seriously shaken my belief in its truth,
had not the great variability in plants made it particularly
difficult to compare their relative degrees of variability.
When we see any part or organ developed in a remarkable
degree or manner in a species, the fair presumption is that
it is of high importance to that species : nevertheless it is in
this case eminently liable to variation. Why should this be
so? On the view that each species has been independently
created, with all its parts as we now see them, I can see no
explanation. But on the view that groups of species are de-
scended from some other species, and have been modified
through natural selection, I think we can obtain some light.
First let me make some preliminary remarks. If, in our
domestic animals, any part or the whole animal be neglected,
and no selection be applied, that part (for instance, the comb
in the Dorking fowl) or the whole breed will cease to have
a uniform character: and the breed may be said to be degen-
erating. In rudimentary organs, and in those which have
been but little specialised for any particular purpose, and
perhaps in polymorphic groups, we see a nearly parallel case ;
for in such cases natural selection either has not or cannot
have come into full play, and thus the organisation is left in
a fluctuating condition. But what here more particularly
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