Dominant as it was, Cuvier's authority was slowly undermined by the
progress of knowledge and the way was prepared for the introduction of
more rational conceptions. The theory of "Catastrophism" was attacked by
several geologists, most effectively by Sir Charles Lyell, who greatly
amplified the principles enunciated by Hutton and Playfair in the
preceding century, and inaugurated a new era in geology. Lyell's
uniformitarian views of the earth's history and of the agencies which
had wrought its changes, had undoubted effect in educating men's minds
for the acceptance of essentially similar views regarding the organic
world. In palaeontology too the doctrine of the immutability of species,
though vehemently maintained and reasserted, was gradually weakening. In
reviewing long series of fossils, relations were observed which pointed
to genetic connections and yet were interpreted as purely ideal.
Agassiz, for example, who never accepted the evolutionary theory, drew
attention to facts which could be satisfactorily interpreted only in
terms of that theory. Among the fossils he indicated "progressive,"
"synthetic," "prophetic," and "embryonic" types, and pointed out the
parallelism which obtains between the geological succession of ancient
animals and the ontogenetic development of recent forms. In Darwin's
words: "This view accords admirably well with our theory." ("Origin of
Species" (6th edition), page 310.) Of similar import were Owen's views
on "generalised types" and "archetypes."

The appearance of "The Origin of Species" in 1859 revolutionised all
the biological sciences. From the very nature of the case, Darwin
was compelled to give careful consideration to the palaeontological
evidence; indeed, it was the palaeontology and modern distribution of
animals in South America which first led him to reflect upon the great
problem. In his own words: "I had been deeply impressed by discovering
in the Pampean formation great fossil animals covered with armour
like that on the existing armadillos; secondly, by the manner in which
closely allied animals replace one another in proceeding southward over
the Continent; and thirdly, by the South American character of most of
the productions of the Galapagos archipelago, and more especially by
the manner in which they differ slightly on each island of the group."
("Life and Letters of Charles Darwin", I. page 82.) In the famous tenth
and eleventh chapters of the "Origin", the pala