6 ESSAY ON CLASSIFICATION. 



tween the conception of a plan and the manner of its execu- 

 tion, upon which classes are founded in contradistinction to 

 the types or branches to which they belong, we might arrive 

 at this distinction by a careful investigation of that single 

 Articulate, as well as by the study of all of them ; and we 

 might recognize its type and ascertain its class-characters 

 as fully as if the type embraced several classes, and these 

 classes thousands of species. Secondly, this animal has 

 a form, which no one would fail to recognize; so that, if 

 form can be shown to be characteristic of families, we 

 could thus determine its family. Again : besides the gene- 

 ral structure, showing the fundamental relations of all the 

 systems of organs of the body to one another in their 

 natural development, our investigation could be carried 

 into the study of the details of that structure in every part, 

 and would thus lead to the recognition of what constitutes 

 everywhere generic characters. Finally: as this animal 

 lias definite relations to the surrounding world, as the in- 

 dividuals living at the time bear definite relations to one 

 another, as the parts of the body show definite propor- 

 tions, and its surface exhibits a special ornamentation, the 

 specific characters could be traced as fully as if a number of 

 other species were at hand for comparison; and they might 

 be drawn and described with sufficient accuracy to dis- 

 tinguish it at any future time from any other set of species 

 discovered afterwards, however closely these new species 

 might be allied to it. In this case, then, we should have 

 to acknowledge a separate branch in the animal kingdom, 

 with a class, a family and a genus, in order to introduce 

 one species into its proper place in the system of animals. 

 But this class would have no order, if orders determine the 

 rank, as ascertained by the complication of structure ; for, 

 where there is but one representative of a type, there is 



