ON THE 



NATURAL HISTORY 



AND 



CLASSIFICATION 



OF 



MONOCARDIAN ANIMALS. 



PART I. 



ON THE NATURE AND RELATIONS OF MONOCARDIAN 

 ANIMALS : AND MORE ESPECIALLY OF FISHES. 



CHAPTER I. 



PRELIMINARY REMARKS. ON THE GENERAL NATURE AND 



RELATIONS OF MONOCARDIAN ANIMALS. 



(l.) W E commenced our review of the animal king- 

 dom with the proposition that it presented certain primary- 

 types of form, wiiich, under a diversity of modifica- 

 tions, pervaded all the classes, and all the divisions^ of 

 this part of creation. The assertion was altogether 

 novel, and somewhat startling, yet it was neither hastily 

 nor presumptuously made. Many years had been de- 

 voted to those researches necessary to ascertain its gene- 

 ral correctness, before we ventured to announce this 

 theory, four years ago, in our " Preliminary Discourse." 

 Ample time has thus been afforded for its refutation ; 

 but so far from this having been accomplished, it has 

 not even been attempted, ^^^e may fairly conclude, 

 therefore, that we are building upon no verv erroneous 



VOL. I. B 



