Influence of circumstances on the Actions of Animals. 963 
bring great differences in the development of their parts, so that 
these differences create and develop some of them, whilst they 
diminish and abolish others. 
But here all goes on by changes wrought in nutrition of the 
vegetable, in its absorptions and its respirations, in the quantity of 
caloric, of light, of air and humidity, which it then habitually 
receives; finally in the superiority which certain of the diverse vital 
movements may exercise over the others. 
Among individuals of the same species, some of which are con- 
tinually well nourished, and under circumstances favorable to their 
development, while others are subjected to opposite conditions, 
there will he produced a difference of development which gradually 
becomes very well marked. How many examples could I not cite 
in regard to animals and vegetables which would confirm this asser- 
tion! Now, if circumstances remaining the same, render the state 
of badly nourished, suffering or languishing individuals habitual 
and constant, their interior organization is finally modified; and 
reproduction among these individuals in question preserves these 
acquired modifications, and at last gives origin to a race very distinct 
from that whose individuals are found continually in circumstances 
favorable to their development. A very dry spring is the reason 
why the grasses of a meadow grow very little and are meagre and 
mean, although they blossom and fruit. A spring time of warm 
and rainy days causes the same grasses to take on much growth, 
and the harvest of hay is then excellent. But if any cause perp: t- 
uates unfavorable circumstances for these plants, they will vary 
proportionally, at first in their appearance or general condition, and 
lly in various particulars of their characters. For example, if 
Some seed of any one of these grasses of the meadow in question, 
be transferred to an elevated locality, dry, arid, stony, and 
much exposed to winds, and there germinate, the plant which wil] 
live in this locality, though always badly nourished, and the indi- 
viduals which it reproduces then continuing to exist under these 
adverse circumstances, there will result a species very different from 
the species living in the meadow, from which it has originated. 
The individuals of this new race would be small, slender in their 
parts, and certain of their organs having developed more than 
others, would then present peculiar proportions. 
