, the maintenance of the individual in the first place, and of
the species in the second. Starting from the axiom that every event
has a cause, we have here the _causa finalis_ manifested in the last
set of phenomena, the _causa materialis_ and _formalis_ in the first,
while the existence of a _causa efficiens_ within the seed or egg and
its product, is a corollary from the phenomena of growth and
metamorphosis, which proceed in unbroken succession and make up the
life of the animal or plant.

Thus, at starting, the egg or seed is matter having a "form" like all
other material bodies. But this form has the peculiarity, in
contradistinction to lower substantial "forms," that it is a power
which constantly works towards an end by means of living organisation.

So far as I know, Leibnitz is the only philosopher (at the same time a
man of science, in the modern sense, of the first rank) who has noted
that the modern conception of Force, as a sort of atmosphere
enveloping the particles of bodies, and having potential or actual
activity, is simply a new name for the Aristotelian Form.[19] In
modern biology, up till within quite recent times, the Aristotelian
conception held undisputed sway; living matter was endowed with "vital
force," and that accounted for everything. Whosoever was not satisfied
with that explanation was treated to that very "plain
argument"--"confound you eternally"--wherewith Lord Peter overcomes
the doubts of his brothers in the "Tale of a Tub." "Materialist" was
the mildest term applied to him--fortunate if he escaped pelting with
"infidel" and "atheist." There may be scientific Rip Van Winkles
about, who still hold by vital force; but among those biologists who
have not been asleep for the last quarter of a century "vital force"
no longer figures in the vocabulary of science. It is a patent
survival of realism; the generalisation from experience that all
living bodies exhibit certain activities of a definite character is
made the basis of the notion that every living body contains an
entity, "vital force," which is assumed to be the cause of those
activities.

It is remarkable, in looking back, to notice to what an extent this
and other survivals of scholastic realism arrested or, at any rate,
impeded the application of sound scientific principles to the
investigation of biological phenomena. When I was beginning to think
about these matters, the scientific world was occasionally agitated by
discus