12 MEANING OF ORDERS. 
CHAPTER V. 
DIFFERENT VIEWS RESPECTING ORDERS. 
Ir 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 defined them, groups in Nature 
founded upon a greater or less complication of 
structure, they must, 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 
