LAMARCK'S THEORY OF EVOLUTION 255 



cupied herself unremittingly in the destruction of all 

 preexistent combinations, I shall undertake to exam- 

 ine under your eyes the great question in natural 

 history — What is a species among organized beings ? 



"When we consider the series of animals, beginning 

 at the end comprising the most perfect and compli- 

 cated, and passing down through all the degrees of 

 this series to the other end, we see a very evident 

 modification in structure and faculties. On the con- 

 trary, if we begin with the end which comprises 

 animals the most simple in organization, the poorest 

 in faculties and in organs — in a word, the most 

 imperfect in all respects — we necessarily remark, as 

 we gradually ascend in the series, a truly progressive 

 complication in the organization of these different 

 animals, and we see the organs and faculties of these 

 beings successively multiplying and diversifying in a 

 most remarkable manner. 



" These facts once known present truths which are, 

 to some extent, eternal ; for nothing here is the prod- 

 uct of our imagination or of our arbitrary princi- 

 ples ; that which I have just explained rests neither 

 on systems nor on any hypothesis : it is only the very 

 simple result of the observation of nature ; hence I 

 do not fear to advance the view that all that one can 

 imagine, from any motives whatever, to contradict 

 these great verities will always be destroyed by the 

 evidence of the facts with which it deals. 



" To these facts it is necessary to add these very 

 important considerations, which observation has led 

 me to perceive, and the basis of which will always be 

 recognized by those who pay attention to them ; they 

 are as follows : 



" Firstly, the exercise of life, and consequently of 

 organic movement, constitutes its activity, tends, 

 without ceasing, not only to develop and to extend 

 the organization, but it tends besides to multiply the 

 organs and to isolate them in special centres {foyers). 



