PRINCIPAL SYSTEMS OF ZOOLOGY 241 



Instead of considering the orders as founded upon a repetition of 

 the characters of higher groups, as Oken would have it, Fitzinger 

 adopts series, as founded upon that idea, and subdivides them further 

 into orders, as above. These series, however, have still less reference 

 to the systems of organs which they are said to represent than either 

 the classes or the higher divisions of the animal kingdom. In these 

 attempts to arrange minor groups of animals into natural series no 

 one can fail to perceive an effort to adapt the frames of our systems 

 to the impression we receive from a careful examination of the nat- 

 ural relations of organized beings. Everywhere we notice such series; 

 sometimes extending only over groups of species, at other times em- 

 bracing many genera, entire families, nay, extending frequently to 

 several families. Even the classes of the same branch may exhibit 

 more or less distinctly such a serial gradation. But I have failed thus 

 far to discover the principle to which such relations may be referred, 

 as far as they do not rest upon complication of structure^® or upon 

 the degree of superiority or inferiority of the features upon which 

 the different kinds of groups are themselves founded. Analogy plays 

 also into the series, but before the categories of analogy have been 

 as carefully scrutinized as those of affinity, it is impossible to say 

 within what limits this takes place. 



CLASSIFICATION OF MACLEAY 



The great merit of the system of MacLeay,^^ and in my opinion 

 it has no other claim to our consideration, consists in having called 

 prominently the attention of naturalists to the difference between 

 two kinds of relationship almost universally confounded before: 

 affinity and analogy. Analogy is shown to consist in the repetition of 



** Compare Chap. II, Sect. in. 



*' I have introduced the classification of William Sharpe MacLeay in this section, 

 not because of any resemblance to those of the German physiophilosophers, but on 

 account of its general character, and because it is based upon an ideal view of the 

 affinities of animals. 



