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 stability, but that they enjoy 

 only a relative stability ; 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 species. 



" 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 sufiE- 

 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. 



" 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 grada- 

 tions 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 pecu- 



