CONTENTS 
NATURAL SELECTION 
I, On toe Law WHICH HAS REGULATED THE INTRODUCTION OF 
New SPEcIES 
Geographical Distribution dependent on Geologic Changes—A Law deduced 
from well-known Geographical and Geological facts—The Form of a 
true system of Classification determined by this Law—Geographical 
Distribution of Organisms—Geological Distribution of the Forms of 
Life— High Organisation of very ancient Animals consistent with 
this Law—Objections to Forbes’s eee of Sia gs ean 
Organs—Conclusion . Pages 8-19 
II. On tHE TENDENCY OF VARIETIES TO DEPART INDEFINITELY 
FROM THE ORIGINAL TYPE 
Introductory Note—Instability of Varieties supposed to prove the per- 
manent distinctness of Species—The Struggle for Existence—The 
Law of Population of Species—The Abundance or Rarity of a Species 
dependent upon its more or less perfect Adaptation to the Conditions 
of Existence—Useful Variations will tend to Increase; useless or 
hurtful Variations to Diminish—Superior Varieties will ultimately 
Extirpate the Original Species—The Partial Reversion of Domesti- 
cated Varieties explained —Lamarck’s Hypothesis very different 
from that now advanced—Conclusion . 7 : . 20-33 
III. Mimicry, AND OTHER PROTECTIVE RESEMBLANCES AMONG 
ANIMALS 
Test of true and false Theories—Importance of the Principle of Utility 
—Popular Theories of Colour in Animals—Importance of Conceal- 
ment as Influencing Colour—Special Modifications of Colour—Theory 
