CHAPTER THIRD. 



NOTICE OF THE PRINCIPAL SYSTEMS OP ZOOLOGY. 



SECTION I. 



GENERAL REMARKS TTPON MODERN SYSTEMS. 



WITHOUT attempting to give an historical account of the 

 leading features of all zoological systems, it is proper that 

 I should here compare critically the practice of modern 

 naturalists with the principles discussed above. With 

 this view, it would hardly be necessary to go back beyond 

 the publication of the "Animal Kingdom", by Cuvier, were 

 it not that Cuvier is still represented by many naturalists, 

 and especially by Ehrenberg 1 and some other German zoo- 

 logists, as favouring the division of the whole animal 

 kingdom into two great groups, one containing the Verte- 

 brates, and the other all the remaining classes, under the 

 name of Invertebrates; while in reality it was he who, 

 dismissing his own earlier views, first introduced into the 

 classification of the animal kingdom that fourfold division 

 which has been the basis of all improvements in modern 

 Zoology. He first showed that animals differ, not only by 

 modifications of one and the same organic structure, but 

 are constructed upon four different plans of structure, 



1 EHRENBERG (C. G.), Die Cerallenthiere des rothen Meercs ; Berlin, 1834, 

 4to., p. 30. 



