CONTENTS. 
I.—On the 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—Geo- 
graphical Distribution of Organisms—Geological Distribution of the 
forms of Life—High Organization of very ancient Animals consistent 
with this Law—Objections to Forbes’ Theory of Polarity—Rudi- 
mentary Organs—Conclusion. =, eee -  « Pp.1—25 
I.—On the Tendency of Varieties to depart indefinitely from the 
Original Type. 
Instability of Varieties supposed to prove the permanent 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 Ori- 
ginal Species The Partial Reversion of Domesticated Varieties 
explained — Lamarck’s kas very different from that now 
advanced—Conclusion . é ‘ ‘ . Pp, 26—44 
IIL.—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 
of Protective Colouring—Objection that Colour as being dangerous 
should not exist in Nature—Mimicry—Mimicry among Lepidoptera 
—Lepidoptera mimicking other Insects—Mimicry among Beetles— 
Beetles mimicking other Insects—Insects mimicking Species of other 
Orders—Cases of Mimicry among the Vertebrata—Mimicry among 
Snakes—Mimicry among Birds—Mimicry among Mammals—Objec- 
