250 LAMARCK, HIS LIFE AND WORK 
sity of circumstances brings about for them a diversity 
of habits, a different mode of existence, and, as the 
result, modifications in their organs and in the shape 
of their parts, one should believe that very gradually 
every living body whatever would vary in its organi- 
zation and its form. 
“ All the modifications that each living being will 
have undergone as the result of change of circum- 
stances which have influenced its nature will doubt- 
less be propagated by heredity (génération). But as 
new modifications will necessarily continue to operate, 
however slowly, not only will there continually be 
found new species, new genera, and even new orders, 
but each species will vary in some part of its struc- 
ture and its form. 
“IT very well know that to our eyes there seems in 
this respect a stadzlity which we believe to be con- 
stant, although it is not so truly; for a very great 
number of centuries may form a period insufficient 
for the changes of which I speak to be marked enough 
for us to appreciate them. Thus we say that the 
flamingo (Phenticopterus) has always had as long legs 
and as long a neck as have those with which we are 
familiar; finally, it is said that all animals whose his- 
tory has been transmitted for 2,000 or 3,000 years 
are always the same, and have lost or acquired noth- 
ing in the process of perfection of their organs and 
in the form of their different parts. We may be as- 
sured that this appearance of s¢tadzlity of things in 
nature will always be taken for reality by the average 
of mankind, because in general it judges everything 
only relatively to itself. 
“But, I repeat, this consideration which has given 
rise to the admitted error owes its source to the very 
great slowness of the changes which have gone on. A 
little attention given to the facts which I am about 
to cite will afford the strongest proof of my assertion. 
“What nature does after a great length of time we 
