LEADING GROUPS OF EXISTING SYSTEMS 159 



belong is carried out are of a higher or lower nature. Orders in any 

 or all classes are of course higher or lower according to the degree 

 of perfection of their representatives, or according to the complica- 

 tion or simplicity of their structure. Families may stand higher or 

 lower as the peculiarities of their form are determined by modifica- 

 tions of more or less important systems of organs. Genera may stand 

 higher or lower as the structural peculiarities of the parts constitut- 

 ing the generic characteristics exhibit a higher or lower grade of 

 development. Species, lastly, may stand one above the other, in the 

 same genus, according to the character of their relations to the sur- 

 rounding world, or that of their representatives to one another. 

 These remarks must make it plain that the respective rank of groups 

 of the same kind among themselves must be determined by the 

 superior or inferior grade of those features upon which they are 

 themselves founded; while orders alone are strictly defined by the 

 natural degrees of structural complications exhibited within the 

 limits of the classes. 



As to the question whether orders constitute necessarily one sim- 

 ple series in their respective classes, I would say that this must depend 

 upon the character of the class itself or the manner in which the plan 

 of the type is carried out within the limits of the class. If the class is 

 homogeneous, that is, if it is not primarily subdivided into sub- 

 classes, the orders will of course form a single series; but if some of 

 its organic systems are developed in a different way from the others, 

 there may be one or several parallel series, each subdivided into 

 graduated orders. This can of course only be determined by a much 

 more minute study of the characteristics of classes than has been 

 made thus far, and mere guesses at such an internal arrangement of 

 the classes into series, as those proposed by Kaup or Fitzinger,^^ can 

 only be considered as the first attempts towards an estimation of the 

 relative value of the intermediate divisions which may exist between 

 the classes and their orders. 



Oken and the physiophilosophers generally have taken a different 

 view of orders. Their idea is that orders represent in their respective 

 classes the characteristic features of the other types of the animal 

 kingdom. As Oken's Intestinal or Gelatinous animals are character- 



" jjohann J. Kaup, Classification der Sdugethiere und Vogel (Darmstadt, 1844); 

 Leopold Fitzinger, Systema Reptilium (Vienna, 1843).] 



