6 ESSAY ON CLASSIFICATION. Part I. 



that extraordinarily diversified type, — how should we introduce that species of animals 

 in our systems? Simply as a genus with one species, by the side of all the other 

 classes with their orders, families, etc., or as a family containing only one genus with 

 one species, or as a class with one order and one genus, or as a class with one 

 family and one genus? And should we acknowledge, by the side of Vertebrata, 

 Mollusks, and Radiata, another type of Articulata, on account of the existence of 

 that one Lobster, or would it be natural to call him by a single name, simply as a 

 species, in contradistinction to all other animals? It was the consideration of this 

 supposed case which led me to the investigations detailed below, which, I hope, may 

 end in the ultimate solution of this apparently inextricable question. 



Though what I have now to say about this supposed case cannot be fully appre- 

 ciated before reading my remarks in the following chapter,^ respecting the character 

 of the different kinds of groups adopted in our systems, it must be obvious that our 

 Lobster, to be what we see these animals are, must have its frame constructed upon 

 that very same plan of structure which it exhibits now ; and, if I should succeed in 

 showing that there is a difference between the conception of a plan and the manner 

 of its execution, upon which classes are founded in contradistinction to the t^'pes 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 then 

 recognize its types and ascertain its class characters as fully as if the type embraced 

 several classes, and this class thousands of species. Then that animal has a form, 

 which no one would flxil to recognize; so that, if form can be shown to be charac- 

 teristic of families, we could thus determine its family. Again: besides the general 

 structure, showing the fundamental relations of all the systems of oi'gans 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 thus lead to the 

 recognition of what constitutes everywhere generic characters. Finally : as this ani- 

 mal has definite relations to the surrounding world, as the individuals living at the 

 time bear definite relations to one another, as the parts of their body show definite 

 proportions, and as the surface of the body exhibits a special ornamentation, the spe- 

 cific 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 

 distinguish it at any future time from any other set of species found afterwards, how- 

 ever 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, to introduce one species to its proper place in the system of animals. 

 But the class would have no order, if orders determine the rank, as ascertained by 



1 See Chap. II. 



