FAMILIES. 243 



have already remarked, that orders and families are the 

 groups upon which zoologists are least agreed, and to the 

 study and characterizing of which they have paid least 

 attention. Does this not arise simply from the fact, that, 

 on the one hand, the difference between ordinal and class 

 characters has not been understood, and only assumed to 

 be a difference of degree; and, on the other hand, that 

 the importance of form, as the prominent character of 

 families, has been entirely overlooked? For, though so 

 few natural families of animals are well characterized, or 

 characterized at all, we cannot open a modern treatise 

 upon any class of animals without finding the genera 

 more or less naturally grouped together, under the head- 

 ing of a generic name with a termination in idee or ince 

 indicating family and sub-family distinctions; and most 

 of these groups, however unequal in absolute value, are 

 really natural groups, though far from designating always 

 natural families, being as often orders or sub-orders as 

 families or sub-families. Yet they indicate the facility with 

 which, almost without study, the intermediate natural 

 groups between the classes and the genera may be pointed 

 out. This arises, in my opinion, from the fact that family 

 resemblance in the animal kingdom is most strikingly ex- 

 pressed in the general form, and that form is an element 

 which falls most easily under our perception, even when 

 the observation is made superficially. But, at the same 

 time, form is most difficult to describe accurately, and 

 hence the imperfection of most of our family character- 

 istics, and the constant substitution for such characters of 

 features which are not essential to the family. To prove 

 the correctness of this view, I would only appeal to the 

 experience of every naturalist. When we see new animals, 

 does not the first glance, that is, the first impression made 



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