TO THE MASTER AND FELLOWS OF CHRIST'S COLLEGE, THIS BOOK IS DEDICATED BY THE EDITOR IN TOKEN OF RESPECT AND GRATITUDE

§ ii. On variation in a state of nature and on the natural

§ iii. On variation in instincts and other mental attributes.

SS iv. and v.

PART II

On the evidence from Geology. (The reasons for

combining the two sections are given in the Intro-

ESSAY OF 1844

PART I

CHAPTER I

ON THE VARIATION OF ORGANIC BEINGS UNDER DOMESTI-

CATION; AND ON THE PRINCIPLES OF SELECTION.

Variation-On the hereditary tendency-Causes of Variation-On Selec-

tion-Crossing Breeds-Whether our domestic races have descended

from one or more wild stocks-Limits to Variation in degree and

kind-In what consists Domestication-Summary

CHAPTER II

57-80

ON THE VARIATION OF ORGANIC BEINGS IN A WILD STATE;

ON THE NATURAL MEANS OF SELECTION; AND ON THE

COMPARISON OF DOMESTIC RACES AND TRUE SPECIES.

66

Variation-Natural means of Selection-Differences between "Races" and

Species"-first, in their trueness or variability-Difference between

"Races" and "Species" in fertility when crossed-Causes of Sterility

in Hybrids-Infertility from causes distinct from hybridisation-Points

of Resemblance between "Races" and "Species"-External characters

of Hybrids and Mongrels-Summary-Limits of Variation 81-111

CHAPTER III

ON THE VARIATION OF INSTINCTS AND OTHER MENTAL

ATTRIBUTES UNDER DOMESTICATION AND IN A STATE OF

NATURE; ON THE DIFFICULTIES IN THIS SUBJECT; AND

ON ANALOGOUS DIFFICULTIES WITH RESPECT TO CORPO-

REAL STRUCTURES.

Variation of mental attributes under domestication-Hereditary habits

compared with instincts-Variation in the mental attributes of wild

animals-Principles of Selection applicable to instincts-Difficulties in

the acquirement of complex instincts by Selection-Difficulties in the

acquirement by Selection of complex corporeal structures. 112-132

PART II

ON THE EVIDENCE FAVOURABLE AND OPPOSED TO THE VIEW

THAT SPECIES ARE NATURALLY FORMED RACES, DESCEND-

ED FROM COMMON STOCKS.

CHAPTER IV

ON THE NUMBER OF INTERMEDIATE FORMS REQUIRED ON THE

THEORY OF COMMON DESCENT; AND ON THEIR ABSENCE

IN A FOSSIL STATE

133-143

CHAPTER V

GRADUAL APPEARANCE AND DISAPPEARANCE OF SPECIES.

Gradual appearance of species-Extinction of species

CHAPTER VI

144-150

ON THE GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS

IN PAST AND PRESENT TIMES.

SECTION FIRST

Distribution of the inhabitants in the different continents-Relation of

range in genera and species-Distribution of the inhabitants in the

same continent-Insular Faunas-Alpine Floras-Cause of the simi-

larity in the floras of some distant mountains-Whether the same

species has been created more than once-On the number of species,

and of the classes to which they belong in different regions 151–174

SECOND SECTION

Geographical distribution of extinct organisms-Changes in geographical

distribution-Summary on the distribution of living and extinct

organic beings

174-182

SECTION THIRD

An attempt to explain the foregoing laws of geographical distribution, on

the theory of allied species having a common descent-Improbability

of finding fossil forms intermediate between existing species 183-197

CHAPTER VII

ON THE NATURE OF THE AFFINITIES AND CLASSIFICATION

OF ORGANIC BEINGS.

Gradual appearance and disappearance of groups-What is the Natural

System -On the kind of relation between distinct groups-Classifica-

tion of Races or Varieties-Classification of Races and Species

similar-Origin of genera and families

198-213