r three thousand
years ago which are like the animals of to-day; but how short a space is
two or three thousand years, as compared with the time which Nature has
had at her disposal! A time infinitely great _qua_ man, is still
infinitely short _qua_ Nature.[241]

"If, however, we turn to animals under confinement, we find immediate
proof that the most startling changes are capable of being produced
after some generations of changed habits. In the sixth chapter we shall
have occasion to observe the power of changed conditions
[_circonstances_] to develop new desires in animals, and to induce new
courses of action; we shall see the power which these new actions will
have, after a certain amount of repetition, to engender new habits and
tendencies; and we shall also note the effects of use and disuse in
either fortifying and developing an organ, or in diminishing it and
causing it to disappear. With plants under domestication, we shall find
corresponding phenomena. Species will thus appear to be unchangeable for
comparatively short periods only."[242]

It is interesting to see that Mr. Darwin lays no less stress on the
study of animals and plants under domestication than Buffon, Dr. Darwin,
and Lamarck. Indeed, all four writers appear to have been in great
measure led to their conclusions by this very study. "At the
commencement of my investigations," writes Mr. Darwin, "it seemed to me
probable that a careful study of domesticated animals and of cultivated
plants would offer the best chance of making out this obscure problem.
Nor have I been disappointed; in this and in all other perplexing cases,
I have invariably found that our knowledge, imperfect though it be, of
variation under domestication, afforded the best and safest clue. I may
venture to express my conviction of the high value of such studies,
though they have been very commonly neglected by naturalists."[243]

In justice to the three writers whom I have named, it should be borne in
mind that they also ventured to express their conviction of the high
value of these studies. Buffon, indeed, as we have seen, gives animals
under domestication the foremost place in his work. He does not treat of
wild animals till he has said all he has to say upon our most important
domesticated breeds,--on whose descent from one or two wild stocks he is
never weary of insisting. It was doubtless because of the opportunities
they afforded him for demonstrating the plasticity of l