182 LAMARCK, HIS LIFE AND WORK 
with man; it began with the simple and ended with 
the complex, or, as we should now say, it proceeded 
from the generalized or undifferentiated to the spe- 
cialized and differentiated. He perceived that many 
forms had been subjected to what he calls degenera- 
tion, or, as we say, modification, and that the progress 
from the simple to the complex was by no means 
direct. Moreover, fossil animals were, according to 
his views, practically extinct species, and stood in the 
light of being the ancestors of the members of our 
existing fauna. In fact, his views, notwithstanding 
shortcomings and errors in classification naturally due 
to the limited knowledge of anatomy and develop- 
ment of his time, have been at the end of a century 
entirely confirmed—a striking testimony to his pro- 
found insight, sound judgment, and_ philosophic 
breadth. 
The reforms that he brought about in the classifi- 
cation of the invertebrate animals were direct and 
positive improvements, were adopted by Cuvier in 
his Régne animal, and have never been set aside. 
We owe to him the foundation and definition of 
the classes of Infusoria, Annelida, Arachnida, and 
Crustacea, the two latter groups being separated from 
the insects. He also showed the distinctness of 
echinoderms from polyps, thus anticipating Leuckart, 
who established the phylum of Ccelenterata nearly 
half a century later. His special work was the classi- 
fication of the great group of Mollusca, which he 
regarded as a class.\ When in our boyhood days we 
attempted to arrange our shells, we were taught to 
use the Lamarckian system, that of Linné having 
