On the Origin of Species by Means of Natural Selection: Or the Preservation ... - Charles Darwin - Google Books

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STRUGGLE FOR EXISTENCE.

Bears on natural selection-The term used in a wide sense-Geo-

metrical powers of increase Rapid increase of naturalised

animals and plants-Nature of the checks to increase-Compe-

tition universal Effects of climate Protection from the

number of individuals-Complex relations of all animals and

plants throughout nature—Struggle for life most severe between

individuals and varieties of the same species; often severe be-

tween species of the same genus-The relation of organism to

organism the most important of all relations

NATURAL SELECTION.

Natural Selection its power compared with man's selection-

power on characters of trifling importance - its power at all ages

and on both sexes Sexual Selection - On the generality of inter-

crosses between individuals of the same species Circumstances

favourable and unfavourable to Natural Selection, namely,

intercrossing, isolation, number of individuals - Slow action

Extinction caused by Natural Selection-Divergence of Cha-

racter, related to the diversity of inhabitants of any small area,

and to naturalisation - Action of Natural Selection, through

Divergence of Character and Extinction, on the descendants

from a common parent― Explains the Grouping of all organic

LAWS OF VARIATION.

Effects of external conditions Use and disuse, combined with

natural selection; organs of flight and of vision - Acclimatisa-

tion - Correlation of growth Compensation and economy of

growth-False correlations — Multiple, rudimentary, and lowly

organised structures variable-Parts developed in an unusual

manner are highly variable: specific characters more variable

than generic secondary sexual characters variable-Species of

the same genus vary in an analogous manner - Reversions to

long-lost characters — Summary

DIFFICULTIES ON THEORY.

Difficulties on the theory of descent with modification-Transitions-

Absence or rarity of transitional varieties-Transitions in habits

of life-Diversified habits in the same species-Species with

habits widely different from those of their allies-Organs of

extreme perfection-Means of transition-Cases of difficulty-

Natura non facit saltum-Organs of small importance-Organs

not in all cases absolutely perfect-The law of Unity of Type

and of the Conditions of Existence embraced by the theory of

Natural Selection

Instincts comparable with habits, but different in their origin-

Instincts graduated - Aphides and ants-Instincts variable —

Domestic instincts, their origin — Natural instincts of the cuckoo,

ostrich, and parasitic bees - Slave-making ants - Hive-bee, its

cell-making instinct - Difficulties on the theory of the Natural

Selection of instincts - Neuter or sterile insects - Summary

Distinction between the sterility of first crosses and of hybrids

Sterility various in degree, not universal, affected by close inter-

breeding, removed by domestication-Laws governing the sterility

of hybrids - Sterility not a special endowment, but incidental

on other differences Causes of the sterility of first crosses and

of hybrids Parallelism between the effects of changed con-

ditions of life and crossing - Fertility of varieties when crossed

and of their mongrel offspring not universal - Hybrids and

mongrels compared independently of their fertility-Summary

ON THE IMPERFECTION OF THE Geological RECORD.

On the absence of intermediate varieties at the present - On

the nature of extinct intermediate varieties; on their number

On the vast lapse of time, as inferred from the rate of deposi-

tion and of denudation - On the poorness of our palæontological

collections On the intermittence of geological formations -

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

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 to

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 chapters

GEOGRAPHICAL DISTRIBUTION.

Present distribution cannot be accounted for by differences in phy-

sical conditions - Importance of barriers — Affinity of the pro-

ductions of the same continent - Centres of creation - Means

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

and by occasional means - Dispersal during the Glacial period

co-extensive with the world

GEOGRAPHICAL DISTRIBUTION-continued.

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 pre-

MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY:

EMBRYOLOGY: RUDIMENTARY ORGANS.

CLASSIFICATION, 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-Extinction se-

parates 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 an early age, and being inherited at a corresponding age

- RUDIMENTARY ORGANS; their origin explained - Summary

-

RECAPITULATION AND CONCLUSION.

Recapitulation of the difficulties on the theory of Natural Selection

-Recapitulation of the general and special circumstances in its

favour - Causes of the general belief in the immutability of

species- How far the theory of natural selection may be

extended-Effects of its adoption on the study of Natural

history-Concluding remarks

INSTRUCTION TO BINDER.

The Diagram to front page 117, and to face the latter part of the

Volume.

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