Lamarck's Introduction of the Element of Time into the Definition
of a Species.
His Theory of Variation and Progression.
Objections to his Theory, how far answered.
Arguments of modern Writers in favour of Progression in the
Animal and Vegetable World.
The old Landmarks supposed to indicate the first Appearance of Man,
and of different Classes of Animals, found to be erroneous.
Yet the Theory of an advancing Series of Organic Beings not
inconsistent with Facts.
Earliest known Fossil Mammalia of low Grade.
No Vertebrata as yet discovered in the oldest Fossiliferous Rocks.
Objections to the Theory of Progression considered.
Causes of the Popularity of the Doctrine of Progression as
compared to that of Transmutation.


CHAPTER 21.

ON THE ORIGIN OF SPECIES BY VARIATION AND NATURAL SELECTION.

Mr. Darwin's Theory of the Origin of Species by Natural Selection.
Memoir by Mr. Wallace.
Manner in which favoured Races prevail in the Struggle for
Existence.
Formation of new Races by breeding.
Hypotheses of definite and indefinite Modifiability equally
arbitrary.
Competition and Extinction of Races.
Progression not a necessary Accompaniment of Variation.