LAMARCK'S THEORY OF EVOLUTION 277, 
by those who have never observed and followed 
nature in her operations. 
“Thus we are assured that that which is taken for 
species among living bodies, and that all the specific 
differences which distinguish these natural produc- 
tions, have no absolute staézlity, but that they enjoy 
only a relative stabzlity ; which it is very important 
to consider in order to fix the limits which we must 
establish in the determination of that which we must 
call speczes. 
“It is known that different places change in nature 
and character by reason of their position, their ‘com- 
position’ [we should say geological structure or fea- 
tures], and their climate; that which is easily per- 
ceived in passing over different places distinguished 
by special characteristics; behold already a cause of 
variation for the natural productious which inhabit 
these different places. But that which is not suff- 
ciently 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 sta- 
bility. 
‘‘ Now, in either case, these changed places pro- 
portionately change the circumstances relative to the 
living bodies which inhabit them, and these produce 
again other influences on those same bodies. 
awe sec from this that i there are: extremes in 
these changes there are also gradations (ances), that 
is to say, steps which are intermediate, and which fill 
up the interval; consequently there are also grada- 
tions in the differences which distinguish that which 
we call speczes. 
“ Indeed, as we constantly meet with such shades 
(or intermediate steps) between these so-called sfeczes, 
we find ourselves forced to descend to the minutest 
details to find any distinctions; the slightest pecu- 
