acts of embryology
On the graduated complexity in each great class
Modification by selection of the forms of immature animals
Importance of embryology in classification
Order in time in which the great classes have first appeared

CHAPTER IX 231-238

ABORTIVE OR RUDIMENTARY ORGANS.

The abortive organs of Naturalists
The abortive organs of Physiologists
Abortion from gradual disuse

CHAPTER X 239-255

RECAPITULATION AND CONCLUSION.

Recapitulation
Why do we wish to reject the Theory of Common Descent?
Conclusion

INDEX 257

Portrait _frontispiece_
Facsimile _to face_ p. 50

INTRODUCTION

We know from the contents of Charles Darwin's Note Book of 1837 that he
was at that time a convinced Evolutionist{1}. Nor can there be any doubt
that, when he started on board the _Beagle_, such opinions as he had
were on the side of immutability. When therefore did the current of his
thoughts begin to set in the direction of Evolution?

{1} See the extracts in _Life and Letters of Charles Darwin_, ii.
p. 5.

We have first to consider the factors that made for such a change. On
his departure in 1831, Henslow gave him vol. I. of Lyell's _Principles_,
then just published, with the warning that he was not to believe what he
read{2}. But believe he did, and it is certain (as Huxley has forcibly
pointed out{3}) that the doctrine of uniformitarianism when applied to
Biology leads of necessity to Evolution. If the extermination of a
species is no more catastrophic than the natural death of an individual,
why should the birth of a species be any more miraculous than the birth
of an individual? It is quite clear that this thought was vividly
present to Darwin when he was writing out his early thoughts in the 1837
Note Book{4}:--

"Propagation explains why modern animals same type as extinct, which is
law almost proved. They die, without they change, like golden pippins;
it is a _generation of species_ like generation _of individuals_."

"If _species_ generate other _species_ their race is not utterly cut
off."

{2} The second volume,--especially important in regard to
Evolution,--reached him in the autumn of 1832, as Prof. Judd has
pointed out in his most interesting paper in _Darwin and