BRANCHES OF THE ANIMAL KINGDOM. 213 



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 kingdom. 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 such 

 characters as 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 observation, and 

 no longer allowing it to be an eternal contest about mere 

 nomenclature. 



At tin's 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 au- 

 thors, and among them some of the most celebrated con- 

 tributors to our knowledge in Natural History, who never 

 busied themselves with Classification, or paid only a 

 passing notice to this subject, whilst they are, by uni- 

 versal consent, considered as the most successful bio- 

 graphers of species ; such are Buffon, Reaumur, Roesel, 



