LAMARCK’S THEORY OF EVOLUTION 255 
cupied herself unremittingly in the destruction of all 
preéxistent combinations, I shall undertake to exam- 
ine under your eyes the great question in natural 
history—What is a sfecies 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). 
