, and precisely at the proper place in which all the
conditions of life to which they were adapted occurred: the
humming-birds at the same time as the flowers; the trichina at the
same time as the pig; the bark-coloured moth at the same time as the
oak, and the wasp-like moth at the same time as the wasp which
protects it. Without processes of selection we should be obliged to
assume a "pre-established harmony" after the famous Leibnitzian model,
by means of which the clock of the evolution of organisms is so
regulated as to strike in exact synchronism with that of the history
of the earth! All forms of life are strictly adapted to the conditions
of their life, and can persist under these conditions alone.

There must therefore be an intrinsic connection between the conditions
and the structural adaptations of the organism, and, _since the
conditions of life cannot be determined by the animal itself, the
adaptations must be called forth by the conditions_.

The selection theory teaches us how this is conceivable, since it
enables us to understand that there is a continual production of what
is non-purposive as well as of what is purposive, but the purposive
alone survives, while the non-purposive perishes in the very act of
arising. This is the old wisdom taught long ago by Empedocles.

II. THE LAMARCKIAN PRINCIPLE

Lamarck, as is well known, formulated a definite theory of evolution
at the beginning of the nineteenth century, exactly fifty years before
the Darwin-Wallace principle of selection was given to the world. This
brilliant investigator also endeavoured to support his theory by
demonstrating forces which might have brought about the
transformations of the organic world in the course of the ages. In
addition to other factors, he laid special emphasis on the increased
or diminished use of the parts of the body, assuming that the
strengthening or weakening which takes place from this cause during
the individual life, could be handed on to the offspring, and thus
intensified and raised to the rank of a specific character. Darwin
also regarded this _Lamarckian principle_, as it is now generally
called, as a factor in evolution, but he was not fully convinced of
the transmissibility of acquired characters.

As I have here to deal only with the theory of selection, I need not
discuss the Lamarckian hypothesis, but I must express my opinion that
there is room for much doubt as to the cooeperation of this princip