SYSTEMS OF ENTOMOLOGY. 41 



the six pieces composing the shell are distinctly seen ; 

 but in profile, there appear only four. Besides the meta- 

 morphosis above described, the Cirrhipedes cast or moult 

 the outer covering of their soft parts, in the manner of 

 the crabs. One of these exuvia, with its various de- 

 tails, will be found on the tenth plate of Mr. Thomp- 

 son's Memoirs, to which we must refer the reader. 



(34.) Having now given the reader a general outline 

 of those annulose classes, which lead from the typical 

 groups to other and more distant forms of the animal 

 world, we shall here introduce a few observations on the 

 arrangement of true insects, previous to commencing 

 their survey. By this plan, the grounds of our dissent 

 from all preceding arrangements will be concentrated 

 in one part of the volume, and much repetition of the 

 same opinions will be prevented. If the principles 

 upon which a classification is based are unsound, the su- 

 perstructure of course must be erroneous, and need not 

 be objected to in detail ; and we shall arrange our re- 

 marks under two heads : 1 . Regarding such systems 

 as are merely framed upon the arbitrary opinion of their 

 authors, who have attached a value to certain cha- 

 racters ; and, 2. Such as have been founded upon a 

 supposed mutual relation of their parts. The former 

 are artificial, the latter natural, methods. 



(35.) So much has been said upon these two modes 

 of arrangement, under which all existing systems of 

 Entomology will arrange themselves, that we shall merely 

 in this place condense their definitions, as introductory 

 to our subsequent remarks. On a former occasion *, we 

 have considered all systems to be artificial, which are 

 not grounded upon any universal principles of arrange- 

 ment, which exhibit the animal series without plan or 

 harmonious relation, and which disregard analogies and 

 affinities. On the other hand, we shall consider those 

 as natural systems, which involve any one or more of 

 these considerations, and which, looking beyond the in- 

 dividual, attempts to ascertain its station in the scale of 



* Geography and Classification of Animals, p. 131. 



