84. GRADATION AMONG ANIMALS. 
CHAPTER VI. 
GRADATION AMONG ANIMALS. 
Wuat, then, is the relation of these larger 
groups to each other, if they. do not stand in a 
connected series from the lowest to the highest ? 
How far are each of the branches and each of 
the classes superior or inferior one to another ? 
All agree, that, while Vertebrates stand at 
the head of the Animal Kingdom, Radiates are 
lowest. There can be no doubt upon this point ; 
for, while the Vertebrate plan, founded upon a 
double symmetry, includes the highest possibili- 
ties of animal organization, there is a certain mo- 
notony of structure in the Radiate plan, in which 
the body is divided into a number of identical 
parts, bearing definite relations to a central verti- 
cal axis. But while all admit that Vertebrates 
are highest and Radiates lowest, how do the Ar- 
ticulates and Mollusks stand to these and to each 
other? To me it seems, that, while both are de- 
cidedly superior to the Radiates and inferior to 
the Vertebrates, we cannot predicate absolute 
superiority or inferiority of organization of either 
