that are supposed to be selected
from and thus accumulated. Are these mainly attributable to the
inherited effects of use and disuse, supplemented by occasional
sports and happy accidents? Or are they mainly due to sports and
happy accidents, supplemented by occasional inherited effects of use
and disuse?

The Lamarckian system has all along been maintained by Mr. Herbert
Spencer, who, in his Principles of Biology, published in 1865,
showed how impossible it was that accidental variations should
accumulate at all. I am not sure how far Mr. Spencer would consent
to being called a Lamarckian pure and simple, nor yet how far it is
strictly accurate to call him one; nevertheless, I can see no
important difference in the main positions taken by him and by
Lamarck.

The question at issue between the Lamarckians, supported by Mr.
Spencer and a growing band of those who have risen in rebellion
against the Charles-Darwinian system on the one hand, and Messrs.
Darwin and Wallace with the greater number of our more prominent
biologists on the other, involves the very existence of evolution as
a workable theory. For it is plain that what Nature can be supposed
able to do by way of choice must depend on the supply of the
variations from which she is supposed to choose. She cannot take
what is not offered to her; and so again she cannot be supposed able
to accumulate unless what is gained in one direction in one
generation, or series of generations, is little likely to be lost in
those that presently succeed. Now variations ascribed mainly to use
and disuse can be supposed capable of being accumulated, for use and
disuse are fairly constant for long periods among the individuals of
the same species, and often over large areas; moreover, conditions
of existence involving changes of habit, and thus of organization,
come for the most part gradually; so that time is given during which
the organism can endeavour to adapt itself in the requisite
respects, instead of being shocked out of existence by too sudden
change. Variations, on the other hand, that are ascribed to mere
chance cannot be supposed as likely to be accumulated, for chance is
notoriously inconstant, and would not purvey the variations in
sufficiently unbroken succession, or in a sufficient number of
individuals, modified similarly in all the necessary correlations at
the same time and place to admit of their being accumulated. It is
vital therefore to the theory