orner of a building,
and which we may suppose are occupied with consulting among
themselves as to the tradition, to pronounce on the duration of the
edifice where they occur: and that going back in their paltry
history to the twenty-fifth generation, they should unanimously
decide that the building which serves to shelter them is eternal, or
at least that it has always existed; because it has always appeared
the same to them; and since they have never heard it said that it
had a beginning. Great things (_grandeurs_) in extent and in
duration are relative.[175]

"When man wishes to clearly represent this truth he will be reserved
in his decisions in regard to stability, which he attributes in
nature to the state of things which he observes there.[176]

"To admit the insensible change of species, and the modifications
which individuals undergo as they are gradually forced to vary their
habits or to contract new ones, we are not reduced to the unique
consideration of too small spaces of time which our observations can
embrace to permit us to perceive these changes; for, besides this
induction, a quantity of facts collected for many years throws
sufficient light on the question that I examine, so that does not
remain undecided; and I can say now that our sciences of observation
are too advanced not to have the solution sought for made evident.

"Indeed, besides what we know of the influences and the results of
heteroclite fecundations, we know positively to-day that a forced
and long-sustained change, both in the habits and mode of life of
animals, and in the situation, soil, and climate of plants, brings
about, after a sufficient time has elapsed, a very remarkable change
in the individuals which are exposed to them.

"The animal which lives a free, wandering life on plains, where it
habitually exercises itself in running swiftly; the birds whose
needs (_besoins_) require them unceasingly to traverse great spaces
in the air, finding themselves enclosed, some in the compartments of
our menageries or in our stables, and others in our cages or in our
poultry yards, are submitted there in time to striking influences,
especially after a series of regenerations under the conditions
which have made them contract new habits. The first loses in large
part its nimbleness, its agility; its body becomes stouter, its
limbs diminish in power and suppleness, an