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, tor alone time there has. beem noticed 
the influence of different states of our organization 
on our character, our propensities (pexchants), our 
actions, and evenour 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. 
“Tf 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 zodlogical 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 
