Introduction

Astronomers might formerly have said that God ordered each planet to move in its particular destiny. In same manner God orders each animal created with certain form in certain country. But how much more simple and sublime power,--let attraction act according to certain law, such are inevitable consequences,--let animal(s) be created, then by the fixed laws of generation, such will be their successors.

From Darwin's Note Book, 1837, p. 101.

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 Modern Science. Cambridge, 1909.

[3] Obituary Notice of C. Darwin, Proc. R. Soc. vol. 44. Reprinted in Huxley's Collected Essays. See also Life and Letters of C. Darwin, ii. p. 179.

[4] See the extracts in the Life and Letters, ii. p. 5.

These quotations show that he was struggling to see in the origin of species a process just as scientifically comprehensible as the birth of individuals. They show, I think, that he recognised the two things not merely as similar but as identical.

It is impossible to know how soon the ferment of uniformitarianism began to work, but it is fair to suspect that in 1832 he had already begun to see that mutability was the logical conclusion of Lyell's doctrine, though this was not acknowledged by Lyell himself.

There were however other factors of change. In his