CHAPTER SECOND. 



LEADING GROUPS OF THE EXISTING SYSTEMS OF ANIMALS. 



SECTION I . 



GREAT TYPES OR BRANCHES OF THE ANIMAL KINGDOM. 



TuE use of the terms types, classes, orders, families, genera, and species, in the 

 systems of Zoology and Botany, is so universal, that it would be natural to suppose 

 that their meaning and extent are well determined and generally understood ; but 

 this is so far from being the case that it may on the coiitrary be said, that there is 

 no subject in Natural History respecting which there exists more uncertainty or 

 a greater want of precision. Indeed, I have failed to find anywhere a definition 

 of the character of most of the more comprehensive of these divisions, Avhile the 

 current views respecting genera and species ai'e very conflicting. Under these cir- 

 cumstances, it has appeared to me particularly desirable to inquire into the founda- 

 tion of these distinctions, and to ascertain, if possible, how far they have a real 

 existence. And, while I hope the results of this inquiry may be welcome and 

 satisfactory, I am free to confess that it has cost me years of labor to arrive at 

 a clear conception of their true character. 



It is such a universal fact in every sphere of intellectual activity, that prac- 

 tice anticipates theory, that no philosopher should be surprised to find that zoologists 

 have adopted instinctively natural groups, in the animal and vegetable kingdoms, 

 oven before the question of the character and of the very existence of such 

 groups in nature was raised. Did not nations speak, understand, and write Greek, 

 Latin, German, and Sanscrit, before it was even suspected that these languages, 

 and so many others, were kindred ? Did not painters produce wondei-s with 

 colors before the nature of light Avas understood ? Had not men been thinking 

 about themselves and the world before logic and metaphysics were taught in schools ? 



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