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234 ORIGIN OF SPECIES
such islands to forms fitted to live on the land? But seals
would necessarily be first converted into terrestrial carnivor-
ous animals of considerable size, and bats into terrestrial
insectivorous animals; for the former there would be no
prey; for the bats ground-insects would serve as food, but
these would already be largely preyed on by the reptiles or
birds, which first colonise and abound on most oceanic islands.
Gradations of structure, with each stage beneficial to a chang-
ing species, will be favoured only under certain peculiar con-
ditions. A strictly terrestrial animal, by occasionally hunting
for food in shallow water, then in streams or lakes, might at
last be converted into an animal so thoroughly aquatic as to
brave the open ocean. But seals would not find on oceanic
islands the conditions favourable to their gradual reconver-
sion into a terrestrial form. Bats, as formerly shown, prob-
ably acquired their wings by at first gliding through the air
from tree to tree, like the so-called flying squirrels, for the
sake of escaping from their enemies, or for avoiding falls;
but when the power of true flight had once been acquired, it
would never be reconverted back, at least for the above pur-
poses, into the less efficient power of gliding through the air.
Bats might, indeed, like many birds, have had their wings
greatly reduced in size, or completely lost, through disuse;
but in this case it would be necessary that they should first
have acquired the power of running quickly on the ground,
by the aid of their hind legs alone, so as to compete with
birds or other ground animals; and for such a change a bat
seems singularly ill-fitted. These conjectural remarks have
been made merely to show that a transition of structure, with
each step beneficial, is a highly complex affair
; and that there
is nothing strange in a transition not having occurred in any
particular case.
Lastly, more than one writer has asked, why have some
animals had their mental powers more highly developed than
others, as such development would be advantageous to all?
Why have not apes acquired the intellectual powers of man ?
Various causes could be assigned; but as they are conjec-
tural, and their relative probability cannot be weighed, it
would be useless to give them. A definite answer to the lat-
ter question ought not to be expected, seeing that no one can
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