in praise of my first book: he wrote
to me later in answer to my appeal for guidance, that "physiological
experiment on animals is justifiable for real investigation; but not for
mere damnable and detestable curiosity. It is a subject which makes me
sick with horror, so I will not say another word about it, else I shall
not sleep to-night." When I prosecuted Slade the spiritualistic
impostor, and obtained his conviction at Bow Street as a common rogue,
Darwin was much interested, and after the affair was over wrote to say
that he was sure that I had been at great expense in effecting what he
considered to be a public benefit, and that he should like to be allowed
to contribute ten pounds to the cost of the prosecution. He was ever
ready in this way to help by timely gifts of money what he thought to be
a good cause, as for instance in the erection of the Zoological Station
of Naples by Dr. Anton Dohrn, to which he gave a hundred pounds. His
most characteristic minor trait which I remember, was his sitting in his
drawing-room at Down in his high-seated arm-chair, and whilst laughing
at some story or joke, slapping his thigh with his right hand and
exclaiming, with a quite innocent and French freedom of speech, "O my
God! That's very good. That's capital." Perhaps one of the most
interesting things that I ever heard him say was when, after describing
to me an experiment in which he had placed under a bell-jar some pollen
from a male flower, together with an unfertilized female flower, in
order to see whether, when kept at a distance but under the same jar,
the one would act in any way on the other, he remarked:--"That's a
fool's experiment. But I love fools' experiments. I am always making
them." A great deal might be written as comment on that statement.
Perhaps the thoughts which it suggests may be summed up by the
proposition that even a wise experiment when made by a fool generally
leads to a false conclusion, but that fools' experiments conducted by a
genius often prove to be leaps through the dark into great discoveries.

As examples of Darwin's writings I have chosen, in addition to those
already mentioned, certain passages from his great book on the 'Origin
of Species,' in which he explains what he understands by the terms
"Natural Selection" and the "Struggle for Existence." These terms
invented by Darwin--but specially the latter--have become "household
words." The history of his thoughts on the subject of the O