Since the foregoing and several of the succeeding chapters were
written, Mr. Herbert Spencer has made his position at once more
clear and more widely understood by his articles "The Factors of
Organic Evolution" which appeared in the Nineteenth Century for
April and May, 1886. The present appears the fittest place in which
to intercalate remarks concerning them.

Mr. Spencer asks whether those are right who regard Mr. Charles
Darwin's theory of natural selection as by itself sufficient to
account for organic evolution.

"On critically examining the evidence" (modern writers never examine
evidence, they always "critically," or "carefully," or "patiently,"
examine it), he writes, we shall find reason to think that it by no
means explains all that has to be explained. Omitting for the
present any consideration of a factor which may be considered
primordial, it may be contended that one of the factors alleged by
Erasmus Darwin and Lamarck must be recognised as a co-operator.
Unless that increase of a part resulting from extra activity, and
that decrease of it resulting from inactivity, are transmissible to
descendants, we are without a key to many phenomena of organic
evolution. UTTERLY INADEQUATE TO EXPLAIN THE MAJOR PART OF THE
FACTS AS IS THE HYPOTHESIS OF THE INHERITANCE OF FUNCTIONALLY
PRODUCED MODIFICATIONS, yet there is a minor part of the facts very
extensive though less, which must be ascribed to this cause."
(Italics mine.)

Mr. Spencer does not here say expressly that Erasmus Darwin and
Lamarck considered inheritance of functionally produced
modifications to be the sole explanation of the facts of organic