204 LAMARCK, HIS LIFE AND WORK 
the animal scale ina sense the inverse of that of nature, 
we find that there exists in the groups composing 
this scale a continuous but irregular modification 
(dégradation) in the organization of animals which 
they comprise, an incre mc Sune ification in the 
organization of these organisms; finally, a proportion- 
ate diminution in the eiaDS: ‘of faculties of these 
beings. 
“This fact once recognized may throw the greatest 
light on the very order which nature has followed in 
the production of all the existing animals; but it 
does not show why the structure of animals in its 
increasing complexity from the more imperfect up to 
the most perfect offers only an irregular gradation, 
whose extent presents a number of anomalies or 
digressions which have no appearance of order in 
their diversity. 
‘““ Now, in seeking for the reason of this singular 
irregularity in the increasing complexity of organi- 
zation of animals, if we should consider the outcome 
of the influences that the infinitely diversified circum- 
stances in all parts of the globe exercise on the gen- 
eral form, the parts, and the very organization of these 
animals, everything will be clearly explained. 
“Tt will, indeed, be evident that the condition in 
which we find all animals is, on one side, the result of 
the increasing complexity of the organization which 
tends to form a regular gradation, and, on the other, 
that it is that of the influences of a multitude of very 
different circumstances which continually tend to 
destroy the regularity in the gradations of the in- 
creasing complexity of the organization. 
“Here it becomes necessary for me to explain the 
meaning I attach to the expression czrcumstances 
zn fluencing the form and structure of animals—namely, 
that in becoming very different they change, with time, 
both their form and organization by proportionate 
modifications. 
