72 MEANING OF ORDERS. 



CHAPTER V. 



DIFFERENT VIEWS RESPECTING ORDERS. 



IT is in the search after the true boundaries 

 and characteristics of orders that we may expect 

 the greatest advance by the naturalists of the 

 present day ; and yet there is now much discre- 

 pancy among them, some mistaking orders for 

 classes, others raising families to the dignity of 

 orders. This want of agreement in their results 

 is not strange, however ; for the recognition of 

 orders is indeed exceedingly difficult. If they 

 are, as I have denned them, groups in Nature 

 founded upon a greater or less complication of 

 structure, they rnus,t,- of course, form a regular 

 gradation within the limits of their class, since 

 comparative perfection implies comparative rank, 

 and a correct estimate of these degrees of com- 

 plication requires an intimate and extensive 

 knowledge of structure throughout the class. 

 There would seem to be an arbitrary element 

 here, that of our individual appreciation of 

 structural character. If one man holds a certain 

 kind of structural characters superior to another, 



