LAMARCK'S THEORY OF DESCENT 



293 



has not received the attention it deserves, doubtless 

 because, very often, it is quite difficult to discover. 

 This fact consists in the influence which circumstances 

 exert on the different organisms subjected to them. 



" In truth, for a long time there has been noticed 

 the influence of different states of our organization 

 on our character, our propensities {penchants), our 

 actions, and even our ideas ; but it seems to me that no 

 one has yet recognized that of our actions and of our 

 habits on our organization itself. Now, as these actions 

 and these habits entirely depend on the circumstances 

 in which we habitually find ourselves, I shall try to 

 show how great is the influence which these circum- 

 stances exercise on the general form, on the condi- 

 tion of the parts, and even on the organization of 

 living bodies. It is therefore this very positive fact 

 which is to be the subject of this chapter. 



" If we have not had numerous occasions to plainly 

 recognize the effects of this influence on certain 

 organisms which we have transported under entirely 

 new and different circumstances, and if we had not 

 seen these effects and the changes resulting from them 

 produced, in a way, under our very eyes, the impor- 

 tant fact in question would have always remained 

 unknown. 



" The influence of circumstances is really continu- 

 ously and everywhere active on living beings, but 

 what renders it difficult for us to appreciate this in- 

 fluence is that its effects only become sensible or 

 recognizable (especially in the animals) at the end of 

 a long period. 



" Before stating and examining the proofs of this 

 fact, which deserves our attention, and which is very 

 important for a zoological philosophy, let us resume 

 the thread of the considerations we had begun to 

 discuss. 



" In the preceding paragraph we have seen that it 

 is now an incontrovertible fact that, in considering 



