on the question.

In the case of the maize it appears that one of the more remarkable and
highly selected American varieties was cultivated in Germany, and in
three years nearly all resemblance to the original parent was lost; and
in the sixth year it closely resembled a common European variety, but
was of somewhat more vigorous growth. In this case no selection appears
to have been practised, and the effects may have been due to that
"reversion to mediocrity" which invariably occurs, and is more
especially marked in the case of varieties which have been rapidly
produced by artificial selection. It may be considered as a partial
reversion to the wild or unimproved stock; and the same thing would
probably have occurred, though perhaps less rapidly, in America itself.
As this is stated by Darwin to be the most remarkable case known to him
"of the direct and prompt action of climate on a plant," we must
conclude that such direct effects have not been proved to be accumulated
by inheritance, independently of reversion or selection.

The remaining part of Mr. Spencer's essay is devoted to a consideration
of the hypothetical action of the environment on the lower organisms
which consist of simple cells or formless masses of protoplasm; and he
shows with great elaboration that the outer and inner parts of these
are necessarily subject to different conditions; and that the outer
actions of air or water lead to the formation of integuments, and
sometimes to other definite modifications of the surface, whence arise
permanent differences of structure. Although in these cases also it is
very difficult to determine how much is due to direct modification by
external agencies transmitted and accumulated by inheritance, and how
much to spontaneous variations accumulated by natural selection, the
probabilities in favour of the former mode of action are here greater,
because there is no differentiation of nutritive and reproductive cells
in these simple organisms; and it can be readily seen that any change
produced in the latter will almost certainly affect the next
generation.[201] We are thus carried back almost to the origin of life,
and can only vaguely speculate on what took place under conditions of
which we know so little.

_The American School of Evolutionists._

The tentative views of Mr. Spencer which we have just discussed, are
carried much further, and attempts have been made to work them out in
great detail, by many Am