324 Agassiz’s Contributions to the 
and lastly, with reference to its last finish, to the execution of the details 
in the individual parts. 
a not be difficult to show, that the differences which exist 
among naturalists in their limitation of classes have arisen from an in- 
and ordinal characters, and have again and again raised orders to 
rank of classes. For we shall see presently, that natural orders must be 
upon the different degrees of complication of structure, exhibited 
within the limits of the classes, while the classes themselves are charac- 
means employed in establishing these ways.”—pp. 145, 146 
An illustration next follows from among the Radiates. The 
Polyps and Acalephs constitute two Classes, differing not 10 the 
complication of their structure, but in thé manner 1n which the 
Radiate plan is carried out. The same is true for the Worms, 
Crustaceans and Insects, the three classes of Articulates; for 
Mammals, Birds, etc., among Vertebrates. 7 
8. Orders.—In no department of classification is there are 
diversity of opinion among naturalists, than in that relating 
the subdivisions termed orders. The following paragraphs ar? 
from the section on this subject. 
“To find out the natural characters of orders from that which nag 
ascertain their relativ I 
ed to designate them, actual 
the animal kingdom, accord 
