Seite - 427 - in The Origin of Species
Bild der Seite - 427 -
Text der Seite - 427 -
CHAPTER XIII
Geographical Distribution—contimied
Distribution of fresh-water productions—On the inhabitants of
oceanic islands—Absence of Batrachians and of terrestrial Mam-
mals—On the relation of the inhabitants of islands to those of
the nearest mainland—On colonisation from the nearest source
with subsequent modification—Summary of the last and present
chapter.
FRESH-WATER PRODUCTIONS
AS lakes and river-systems are separated from each
l\ Other by barriers of land, it might have been thought
-*--^ that fresh-water productions would not have ranged
widely within the same country, and as the sea is apparently
a still more formidable barrier, that they would never have
extended to distant countries. But the case is exactly the re-
verse. Not only have many fresh-water species, belonging
to different classes, an enormous range, but allied species
prevail in a remarkable manner throughout the world. When
first collecting in the fresh waters of Brazil, I well remember
feeling much surprise at the similarity of the fresh-water
insects, shells, &c., and at the dissimilarity of the surroimd-
ing terrestrial beings, compared with those of Britain.
But the wide ranging power of fresh-water productions
can, I think, in most cases be explained by their having be-
come fitted, in a manner highly useful to them, for short
and frequent migrations from pond to pond, or from stream
to stream, within their own countries; and liability to wide
dispersal would follow from this capacity as an almost neces-
sary consequence. We can here consider only a few cases;
of these, some of the most difficult to explain are presented
by fish. It was formerly believed that the same fresh-water
species never existed on two continents distant from each
other. But Dr. Giinther has lately shown that the Galaxias
427
zurĂĽck zum
Buch The Origin of Species"
Inhaltsverzeichnis
- 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