Influence of circumstances on the Actions of Animals. 961 
only become sensible or recognizable (especially among animals) 
after a long time. 
Before showing and examining the proofs of these facts, which 
deserve our attention, and which are of great importance to Philo- 
sophical Zoology, let us again take up the thread of considerations 
which we have already had in hand. 
In the preceding chapter we have seen that it is at present an 
incontestable fact that in considering the animal scale in an inverse 
sense to that of nature, we find that there exists in the bodies which 
compose this scale a continual but irregular degradation in the 
organization of the animals which compose it; a growing simplifi- 
cation of the organization of living bodies, and finally a propor- 
tional diminution in the number of faculties of these beings. 
This well-known fact throws the greatest light upon the order 
which nature has followed in the production of all existing animals ; 
but it does not point out to us why the organization of animals in its 
growing constitution, from the most imperfect up to the most 
perfect, shows only irregular gradation, of which the facies presents 
numerous anomalies or digressions, having no appearance of order 
in their diversity. 
Now, in searching for the reason of this singular irregularity in 
the growing constitution of the organization of animals, if we 
consider the result of the influence which circumstances, infinitely 
diversified in all parts of the globe, exercise on the general form, 
the parts, and the organization itself of the animals, all then will 
be clearly explained. 
It will be, in fact, evident that the state in which we see all 
animals, is, on one side, the product of the growing constitution 
of the organization which tends to form a regular gradation, and, 
on the other side, that it is the influence of a multitude of very 
different circumstances which are tending continually to destroy the 
regularity in the gradation of the growing constitution of the 
organization. 
Here it becomes necessary to explain myself as to the meaning 
which I attach to these expressions: The eirewmstances influence 
orm and organization of animals, that is to say, that in becoming 
very different they change in time both their form and their organ- 
wation itself, by proportional modifications. Surely, if these 
