ly survive in
times of difficulty, while the unmodified individuals perish: offspring
therefore is more frequently left by the favourably modified animal, and
thus little by little the whole species will come to inherit the
modification. Hence the survival of the fittest becomes a means of
modification, though it is no cause of variation.

It will appear more clearly later on how much this amounts to. I will
for the present content myself with the following quotation from the
late Mr. G. H. Lewes in reference to it. Mr. Lewes writes:--

"Mr. Darwin seems to imply that the external conditions which cause a
variation are to be distinguished from the conditions which accumulate
and perfect such variation, that is to say, he implies a radical
difference between the process of variation and the process of
selection. This I have already said does not seem to me acceptable; the
selection I conceive to be simply the variation which has
survived."[354]

Certainly those animals and plants which are best fitted for their
environment, or, as Lamarck calls it, "_circonstances_"--those animals,
in fact, which are best fitted to comply with the conditions of their
existence--are most likely to survive and transmit their especial
fitness. No one would admit this more readily than Lamarck. This is no
theory; it is a commonly observed fact in nature which no one will
dispute, but it is not more "a means of modification" than many other
commonly observed facts concerning animals.

Why is "the survival of the fittest" more a means of modification than,
we will say, the fact that animals live at all, or that they live in
successive generations, being born, continuing their species, and dying,
instead of living on for ever as one single animal in the common
acceptation of the term; or than that they eat and drink?

The heat whereby the water is heated, the water which is turned into
steam, the piston on which the steam acts, the driving wheel, &c., &c.,
are all one as much as another a means whereby a train is made to go
from one place to another; it is impossible to say that any one of them
is the main means. So (_mutatis mutandis_) with modification. There is
no reason therefore why "the survival of the fittest" should claim to
be an especial "means of modification" rather than any other necessary
adjunct of animal or vegetable life.

I find that the late Mr. G. H. Lewes has insisted on this objection in
his 'Physical Basis of Mind.