in another sense, as "fluctuations." Darwin recognized both lines of
evolution; Wallace disregarded the sudden changes and proposed
fluctuations [8] as the exclusive factor. Of late, however, this point
of view has been abandoned by many investigators, especially in America.

The actual occurrence of mutations is recognized, and the battle rages
about the question, as to whether they are be regarded as the principal
means of evolution, or whether slow and gradual changes have not also
played a large and important part.

The defenders of the theory of evolution by slow accumulation of slight
fluctuations are divided into two camps. One group is called the
Neo-Lamarckians; they assume a direct modifying agency of the
environment, producing a corresponding and useful change in the
organization. The other group call themselves Darwinians or
selectionists, but to my mind with no other right beyond the arbitrary
restriction of the Darwinian principles by Wallace. They assume
fluctuating variations in all directions and leave the choice between
them to the sieve of natural selection.

Of course we are far from a decision between these views, on the sole
ground of the facts as known at present. Mutations under observation are
as yet very rare; enough to indicate the possible and most probable
ways, but no more. On the other hand the accumulation of fluctuations
does not transgress relatively narrow [9] limits as far as the present
methods of selection go. But the question remains to be solved, whether
our methods are truly the right ones, and whether by the use of new
principles, new results might not cause the balance of opinion to favor
the opposite side.