LAMARCK’S THEORY OF EVOLUTION 249 
APPENDIX (p. 141). 
On Species in Living Bodies. 
“T have for a longtime thought that speczes were 
constant in nature, and that they were constituted 
by the individuals which belong to each of them. 
“Tam now convinced that I was in error in this 
respect, and that in reality only individuals exist in 
nature. 
“ The origin of this error, which I have shared with 
many naturalists who still hold it, arises from the long 
duration, in relation to us, of the same state of things 
in each place which each organism inhabits; but this 
duration of the same state of things for each place 
has its limits, and with much time it makes changes 
in each point of the surface of the globe, which pro- 
duces changes in every kind of circumstances for the 
organisms which inhabit it. 
“ Indeed, we may now be assured that nothing on 
the surface of the terrestrial globe remains in the 
same state. Everything, after a while, undergoes 
different changes, more or less prompt, according to 
the nature of the objects and of circumstances. Ele- 
vated areas are constantly being lowered, and the 
loose material carried down to the lowlands. The 
beds of rivers, of streams, of even the sea, are gradu- 
ally removed and changed, as also the climate ;* ina 
word, the whole surface of the earth gradually under- 
goes a change in situation, form, nature, and aspect. 
We see on every hand what ascertained facts prove; 
it is only necessary to observe and to give one’s at- 
tention to be convinced of it. 
“ However, if, relatively to living beings, the diver- 
* T have cited the incontestable proofs in my //ydrogéologie, and I 
have the conviction that one day all will be compelled to accept these 
great truths. 
