322 LAMARCK, HIS LIFE AND WORK 
would tend to widen the pelvis and to cause the 
cotyloid cavities to be directed backward ; 
“s. Finally, that a great number of their bones 
would become fused, and hence several parts of their 
skeleton would assume an arrangement and a figure 
conformed to the habits of these animals, and con- 
trary to what would be necessary for them to have 
for other habits. 
“Indeed, this can never be denied, because, in fact, 
nature on a thousand other occasions shows us, in the 
power exercised by circumstances on habits, and in 
that of the influence of habits on forms, dispositions, 
and the proportion of the parts of animals, truly 
analogous facts. 
“A great number of citations being unnecessary, 
we now see to what the case under discussion is re- 
duced. 
“The fact is that divers animals have each, accord- 
ing to their genus and their species, special habits, 
and in all cases an organization which is perfectly 
adapted to these habits. 
“From the consideration of this fact, it appears 
that we should be free to admit either one or the 
other of the following conclusions, and that only one 
of them is susceptible of proof. 
“ Conclusion admitted up to this day; Nature (or its 
Author), in creating the animals, has foreseen all the 
possible kinds of circumstances in which they should 
live, and has given to each species an unchanging 
organization, as also a form determinate and invariable 
in its different parts, which compels each species to 
live in the places and in the climate where we find it, 
and has there preserved its known habits. 
“ My own conclusion; Nature, in producing in suc- 
cession every species of animal, and beginning with the 
least perfect or the simplest to end her work with the 
most perfect, has gradually complicated their struct- 
ure ; and these animals spreading generally throughout 
