Influence of circumstances on the Actions of Animals. 1063 
propagated and passes thus into all the individuals which follow, and 
who are placed in the same circumstances, without which they would 
be obliged to acquire it in the same manner in which it has already 
been created. Moreover, in these reproductive unions, the mix- 
ture between individuals which have different qualities and forms, 
necessarily opposes the constant propagation of these qualities an 
forms. ' 
I.—It is this which prevents in man, accidental qualities or 
defects due to circumstances to which he is exposed from preserving 
and propagating themselves by generation. 
II.—If two individuals who have acquired peculiarities of 
form or defects be united, in this case they will reproduce the 
same peculiarities in successive generations. And if they restrict 
themselves to like unions, a particular and distinct race will then 
be formed. But the perpetual mixture between individuals which 
have not the same peculiarities of forms will destroy all the pecu- 
liarities acquired by particular circumstances. From this one can 
be assured that if distances of habitation had not separated men, 
the crossing, by generation, would have destroyed the general 
characters which distinguish different nations. If I should 
pass in review all the classes, all the orders, all the genera, 
and all the species of animals which exist, I would be able to 
show that the conformation of individuals and of their parts, that 
their organs, their functions, ete., ete., are everywhere only the result 
of circumstances in which every species finds itself surrounded by 
nature, and of the habits which the individuals which compose it 
have been obliged to adopt, and that they are not the result of an 
existing primitive form which has forced these animals to adopt 
their habits. 
It is known that the animal which is called the Ai, or the sloth, 
(Bradypus tridactylus), is constantly in a state of so great feebleness 
that it executes very slow and limited movements, and that it walks 
with great difficulty on the ground. Its movements are so slow 
that it is claimed that it is able to take only fifty steps in a day. 
It is known also that the organization of this animal is in all 
respects harmonious with its condition of feebleness or its inability 
to walk, and that if it wished to make other movements than those 
Which it is known to execute, it would not be able. If we sup- _ 
