302 LAMARCK, HIS LIFE AND WORK 
ments to recognize that in each one of these places 
the order of things that he discovers there has not 
always been the same, and to perceive that it will 
change more 
““The races of animals which live in each of these 
places should, then, retain their customary habits 
there also for a long time; hence to us seems an ap- 
parent constancy of races which we call spectes—con- 
stancy which has originated among us the idea that 
these races are as ancient as nature. 
“ But in the different points of the earth’s surface 
which can be inhabited, nature and the situation of 
the places and climates constitute there, for the ani- 
mals as for the plants, different circumstances of all 
sorts of degrees. The animals which inhabit these 
different places should then differ from each other, 
not only on account of the state of nature of the 
organization in each race, but, besides, by reason of 
the habits that the individuals of each race there are 
forced to have; so, in proportion as he traverses the 
larger parts of the earth’s surface the observing 
naturalist sees circumstances changing in a manner 
somewhat noticeable; he constantly sees that the 
species change proportionately in their characters. 
“ Now, the true order of things necessary to con- 
sider in all this consists in recognizing : 
“1, That every slight change maintained under 
the circumstances where occur each race of animals, 
brings about in them a real change in their wants. 
“2, That every change in the wants of animals 
necessitates in them other movements (ac/zons) to 
satisfy the new needs, and consequently other habits. 
“3, That every new want necessitating new actions 
to sate it, demands of the animal w hich feels it both 
the more frequent use of such of its parts of which 
before it made less use, which develops and consider- 
ably enlarges them, and the use of new parts which 
necessity has caused to insensibly develop in it by 
