PREFACE

THE author has found it impossible to compress into two volumes, according to his original plan, the wide range of subjects which must be discussed, in order fully to explain his views respecting the causes of geological phenomena. As it will, therefore, be necessary to extend the "Principles of Geology" to three volumes, he prefers the publication of the present part without delay, because it brings to a close one distinct branch of the inquiry, the study of which will be found absolutely essential to the understanding of the theories hereafter to be proposed. Considerable progress has already been made in the remainder of the work, which will shortly be laid before the public.

London, December 8th, 1831.

CONTENTS.

VOL. II.

PAGE

CHAPTER I.

Changes of the Organic World now in progress-Division of the Subject—

-Examination of the question, Whether Species have a real existence in

Nature?-Importance of this question in Geology-Sketch of Lamarck's

arguments in favour of the Transmutation of Species, and his conjectures

respecting the Origin of existing Animals and Plants-His Theory of the

transformation of the Orang Outang into the Human Species

CHAPTER II.

Recapitulation of the arguments in favour of the theory of transmutation of

species—Their insufficiency—The difficulty of discriminating species mainly

attributable to a defective knowledge of their history-Some mere varieties

possibly more distinct than certain individuals of distinct species-Variability

in a species consistent with a belief that the limits of deviation are fixed-No

facts of transmutation authenticated-Varieties of the Dog-The Dog and

Wolf distinct Species-Mummies of various animals from Egypt identical in

character with living individuals-Seeds and plants from the Egyptian

tombs-Modifications produced in plants by agriculture and gardening

CHAPTER III.·

Variability of a species compared to that of an individual-Species which

are susceptible of modification may be altered greatly in a short time, and in

a few generations; after which they remain stationary-The animals now

subject to man had originally an aptitude to domesticity—Acquired pecu-

liarities which become hereditary have a close connexion with the habits or

instincts of the species in a wild state-Some qualities in certain animals

have been conferred with a view of their relation to man- -Wild elephant

domesticated in a few years, but its faculties incapable of further develop-

ment

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CHAPTER IV.

Consideration of the question whether species have a real existence in

nature, continued-Phenomena of hybrids-Hunter's opinions as to mule

animals-Mules not strictly intermediate between the parent species-Hybrid

plants-Experiments of Kölreuter-The same repeated by Wiegmann—

Vegetable hybrids prolific throughout several generations-Why so rare in a

wild state-Decandolle's opinion respecting hybrid plants-The phenomena

of hybrids confirms the doctrine of the permanent distinctness of species-

Theory of the gradation in the intelligence of animals as indicated by the

facial angle-Discovery of Tieddemann that the brain of the fœtus in mam-

malia assumes successively the form of the brain of a fish, reptile, and bird—

Bearing of this discovery on the theory of progressive development and

transmutation-Recapitulation

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CHAPTER V.

Laws which regulate the geographical distribution of species-Analogy of

climate not attended with identity of species-Botanical geography-Stations

-Habitations-Distinct provinces of indigenous plants-Vegetation of

islands-Marine vegetation-In what manner plants become diffused-

Effects of wind, rivers, marine currents-Agency of animals-Many seeds

pass through the stomachs of animals and birds undigested-Agency of man

in the dispersion of plants, both voluntary and involuntary-Its analogy to

that of the inferior animals

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CHAPTER VI.

Geographical distribution of Animals-Buffon on the specific distinctness

of the quadrupeds of the old and new world-Different regions of indigenous

mammalia-Quadrupeds in islands-Range of the Cetacea-Dissemination

of quadrupeds-Their powers of swimming-Migratory instincts-Drifting

of quadrupeds on ice-floes-On floating islands of drift-timber-Migrations of

Cetacea-Habitations of Birds-Their migrations and facilities of diffusion

-Distribution of Reptiles and their powers of dissemination

CHAPTER VII.

Geographical distribution and migrations of fish-of testacea-Causes

which limit the extension of many species-Their mode of diffusion-Geo-

graphical range of zoophytes-Their powers of dissemination-Distribution

of insects-Migratory instincts of some species--Certain types characterize

particular countries—Their means of dissemination—Geographical distribu-

tion and diffusion of man-Speculations as to the birth-place of the human

species-Progress of human population-Drifting of canoes to vast dis-

tances-On the involuntary influence of man in extending the range of many

other species

CHAPTER VIII.

Theories respecting the original introduction of species-Proposal of an

hypothesis on this subject—Supposed centres or foci of creation-Why the

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