termination of that which we must call _species_.

"It is known that different places change in nature and character by
reason of their position, their 'composition' [we should say
geological structure or features], and their climate; that which is
easily perceived in passing over different places distinguished by
special characteristics; behold already a cause of variation for the
natural productions which inhabit these different places. But that
which is not sufficiently known, and even that which people refuse to
believe, is that each place itself changes after a time, in exposure,
in climate, in nature, and in character, although with a slowness so
great in relation to our period of time that we attribute to it a
perfect _stability_.

"Now, in either case, these changed places proportionately change
the circumstances relative to the living bodies which inhabit them,
and these produce again other influences on those same bodies.

"We see from this that if there are extremes in these changes there
are also gradations (_nuances_), that is to say, steps which are
intermediate, and which fill up the interval; consequently there are
also gradations in the differences which distinguish that which we
call _species_.

"Indeed, as we constantly meet with such shades (or intermediate
steps) between these so-called _species_, we find ourselves forced
to descend to the minutest details to find any distinctions; the
slightest peculiarities of form, of color, of size, and often even
of differences only perceived in the aspect of the individual
compared with other individuals which are related to it the more by
their relations, are seized upon by naturalists to establish
specific differences; so that, the slightest varieties being
reckoned as species, our catalogues of species grow infinitely
great, and the name of the productions of nature of the most
interest to us are, so to speak, buried in these enormous lists,
become very difficult to find, because now the objects are mostly
only determined by characters which our senses can scarcely enable
us to perceive.

"Meanwhile we should remember that nothing of all this exists in
nature; that she knows neither classes, orders, genera, nor species,
in spite of all the foundation which the portion of the natural
series which our collection contains has seemed to afford them; and
that of organic or living b