Influence of circumstances on the Actions of Animals. 967 
sity which necessarily results from the progress of the composition 
of the organization in each animal. 
In every place where animals have been able to live, the circum- 
stances which have established there an order of things which has 
continued for a long time the same, and change is there really so 
slow that man has not been able to observe it directly. He is 
obliged to consult records, and monuments, and to recognize that 
in each one of these localities the order of things which he finds 
there has not always been the same, and thus to infer that it will 
still change. The races of animals which live in any of these 
places must preserve their habits for a long time, hence to us the 
apparent constancy of races which we call species—constancy which 
has given us the idea that these races are therefore as ancient as 
nature, 
But at different points on the surface of the globe which are hab- 
itable, the nature and situation of the localities and the climates 
constitute for animals, as for vegetables, different circumstances in 
all kinds of degrees. Animals which inhabit these different local- 
ities must then necessarily become different from each other, not 
only by reason of the state of growth of the organization in each case, 
but besides by reason of habits which individuals of each race are 
forced to adopt. Therefore, in a measure, in traveling over great 
portions of the surface of the earth, the observing naturalist sees 
circumstances change in a gradual manner ; he perceives constantly 
also that the species change proportionally in their characters. 
Now, the true order of things, which is the question to consider 
in all this, consists in recognizing,— 
Ist. That every change, of any importance, in the circumstances 
in which each race of animals exists, continually maintained, effects 
a real change in their necessities. 
2d. That all change in the wants of animals necessitates for 
them new actions, in order to satisfy new wants, and consequently 
other habits. 
3d. That every new want necessitating new actions to satisfy 
it, requires from the animal which experiences it, more frequent. 
employment of some of its parts of which it made less use before. 
Thereby are developed and enlarged considerably the new parts 
Which the wants have insensibly created in it by the efforts of its 
