on an average, three hundred words.

That the editorship of these Essays has been entrusted to a Cambridge
Professor of Botany must be gratifying to all concerned in their
production and in their perusal, recalling as it does the fact that
Charles Darwin's instructor in scientific methods was his lifelong
friend the late Rev. J.S. Henslow at that time Professor of Botany in
the University. It was owing to his recommendation that his pupil was
appointed Naturalist to H.M.S. "Beagle", a service which Darwin himself
regarded as marking the dawn of his scientific career.

Very sincerely yours,

J.D. HOOKER.

II. DARWIN'S PREDECESSORS. By J. Arthur Thomson.

Professor of Natural History in the University of Aberdeen.

In seeking to discover Darwin's relation to his predecessors it is
useful to distinguish the various services which he rendered to the
theory of organic evolution.

(I) As everyone knows, the general idea of the Doctrine of Descent
is that the plants and animals of the present-day are the lineal
descendants of ancestors on the whole somewhat simpler, that these again
are descended from yet simpler forms, and so on backwards towards the
literal "Protozoa" and "Protophyta" about which we unfortunately know
nothing. Now no one supposes that Darwin originated this idea, which in
rudiment at least is as old as Aristotle. What Darwin did was to make
it current intellectual coin. He gave it a form that commended itself
to the scientific and public intelligence of the day, and he won
wide-spread conviction by showing with consummate skill that it was
an effective formula to work with, a key which no lock refused. In
a scholarly, critical, and pre-eminently fair-minded way, admitting
difficulties and removing them, foreseeing objections and forestalling
them, he showed that the doctrine of descent supplied a modal
interpretation of how our present-day fauna and flora have come to be.

(II) In the second place, Darwin applied the evolution-idea to
particular problems, such as the descent of man, and showed what a
powerful organon it is, introducing order into masses of uncorrelated
facts, interpreting enigmas both of structure and function, both
bodily and mental, and, best of all, stimulating and guiding further
investigation. But here again it cannot be claimed that Darwin was
original. The problem of the descent or ascent of man, and other
particular cases of evolution, had attracted not a few natural