LEADING GROUPS OF EXISTING SYSTEMS 143 



that all these groups would differ only by the quantity of their char- 

 acters and not by the quality, as if the elements of structure in ani- 

 mals were all of the same kind; as if the form, for instance, was an 

 organic element of the same kind as the complication of structure, 

 and as if the degree of complication implied necessarily one plan of 

 structure to the exclusion of another. I trust I shall presently be able 

 to show that it is to a neglect of these considerations that we must 

 ascribe the slow progress which has been made in the philosophy of 

 classification. 



Were it possible to show that all these groups do not differ in 

 quantity and are not merely divisions of a wider or more limited 

 range, but are based upon different categories of characters, genera 

 would be called genera by all, whether they differ much or little one 

 from the other, and so would families be called families, orders be 

 called orders, etc. Could species, for instance, be based upon absolute 

 size, genera upon the structure of some external parts of the body, 

 families upon the form of the body, orders upon the similarity of 

 the internal structure or the like, it is plain that there could not be 

 two opinions respecting these groups in any class of the animal king- 

 dom. But as the problem is not so simple in nature, it was not until 

 after the most extensive investigations, that I obtained the clue to 

 guide me through this labyrinth. I knew, for instance, that though 

 naturalists have been disputing and are still disputing about species 

 and genera, they all distinguished the things themselves in pretty 

 much the same manner. What A would call a species, B called only 

 a variety or a race; but then B might call a sub-genus the very same 

 aggregate of individuals which A called a species; or what A called a 

 genus was considered by B as a family or an order. Now it was this 

 something called no matter how for which I tried to find out char- 

 acters which would lead all to call it by the same name; thus limiting 

 the practical difficulty in the application of the name to a question 

 of accuracy in the observations, and no longer allowing it to be an 

 eternal contest about mere nomenclature. 



At this stage of my investigation it struck me that the character 

 of the writings of eminent naturalists might throw some light upon 

 the subject itself. There are authors, and among them some of the 

 most celebrated contributors to our knowledge in Natural History, 

 who never busied themselves with classification, or paid only a pass- 



