84 GRADATION AMONG ANIMALS. 



CHAPTER VI. 



GRADATION AMONG ANIMALS. 



WHAT, 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 



