THE

ORIGIN OF SPECIES

BY MEANS OF NATURAL SELECTION

OR THE PRESERVATION OF FAVORED RACES IN
THE STRUGGLE FOR LIFE

BY

CHARLES DARWIN, M. A., LL. D., F. R. S.

CONTENTS OF VOL. II.

CHAPTER IX.

HYBRIDISM.

Distinction between the sterility of first crosses and of hybrids—

Sterility various in degree, not universal, affected by close

interbreeding, removed by domestication-Laws governing the

sterility of hybrids-Sterility not a special endowment, but

incidental on other differences, not accumulated by natural

selection-Causes of the sterility of first crosses and of hybrids

-Parallelism between the effects of changed conditions of

life and of crossing-Dimorphism and Trimorphism-Fertility

of varieties when crossed, and of their mongrel offspring not

universal-Hybrids and mongrels compared independently of

their fertility-Summary

Page 1

CHAPTER X.

ON THE IMPERFECTION OF THE GEOLOGICAL RECORD.

On the absence of intermediate varieties at the present day-On

the nature of extinct intermediate varieties; on their number

-On the lapse of time, as inferred from the rate of denudation

and of deposition-On the lapse of time as estimated by years

-On the poorness of our palæontological collections-On the

intermittence of geological formations-On the denudation of

granitic areas-On the absence of intermediate varieties in any

one formation-On the sudden appearance of groups of species

-On their sudden appearance in the lowest known fossiliferous

strata-Antiquity of the habitable earth

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CHAPTER XI.

ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS.

On the slow and successive appearance of new species-On their

different rates of change-Species once lost do not reappear―

Groups of species follow the same general rules in their appear-

ance and disappearance as do single species-On Extinction-

On simultaneous changes in the forms of life throughout the

world-On the affinities of extinct species to each other and 10

living species-On the state of development of ancient forms—

On the succession of the same types within the same areas-

Summary of preceding and present chapter

Page 89

CHAPTER XII.

GEOGRAPHICAL DISTRIBUTION.

Present distribution cannot be accounted for by differences in

physical conditions-Importance of barriers-Affinity of the

productions of the same continent-Centres of creation-Meas

of dispersal, by changes of climate and of the level of the land,

and by occasional means—Dispersal during the Glacial period

-Alternate Glacial periods in the north and south

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CHAPTER XIII.

GEOGRAPHICAL DISTRIBUTION-continued.

Distribution of fresh-water productions-On the inhabitants of

oceanic islands-Absence of Batrachians and of terrestrial

Mammals-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..

.. 171

CHAPTER XIV.

MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY:

EMBRYOLOGY: RUDIMENTARY ORGANS.

CI ASSIFICATION, groups subordinate to groups-Natural system-

Rules and difficulties in classification, explained on the theory

of descent with modification-Classification of varieties-

Descent always used in classification-Analogical or adaptive

characters-Affinities, general, complex, and radiating-Ex-

tinction separates and defines groups-MORPHOLOGY, between

members of the same class, between parts of the same

individual-EMBRYOLOGY, laws of, explained by variations not

supervening at any early age, and being inherited at a

corresponding age—RUDIMENTARY ORGANS; their origin ex-

plained-Summary

.. Page 202

CHAPTER XV.

RECAPITULATION AND CONCLUSION.

Recapitulation of the objections to the theory of Natural Selection

-Recapitulation of the general and special circumstances in

its favour-Causes of the general belief in the immutability of

sp cies-How far the theory of Natural Selection may be

extended-Effects of its adeption on the study of Natural

History-Concluding remarks ..

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