INTRODUCTORY REMARKS. XV11 



science, in which no improvement has been made, 

 and which would alone entitle him to the thanks 

 of posterity. 



But the system of Linnaeus was destined to yield 

 to a successor. It was avowedly artificial ; but, from 

 the imperfect state of zoological knowledge in his 

 day, it was impossible that it should be otherwise. 

 The impulse, however, which it gave to science was 

 soon perceived in the vast and rapid influx of new 

 information ; and, soon after the beginning of the 

 present century, materials sufficient were in the 

 possession of scientific men to enable M. Cuvier, 

 in concert with his distinguished associates, to put 

 forth a new arrangement of the " Animal Kingdom," 

 founded on its organization. This distribution we 

 purpose mainly to follow in the present treatise, not 

 because it is not susceptible of improvement, but be- 

 cause it has attained a well-deserved celebrity, is the 

 best known and the most used. He wisely selected the 

 NERVOUS SYSTEM as the basis of his great divisions, 

 as this appears to be more essentially connected with 

 animal life than any other organs. He considered 

 that we find in Nature " four principal forms, four 

 general plans, on which all animals seem to have 

 been modelled ;" and accordingly he distributed the 

 Animal Kingdom into four principal Divisions, which 

 he named VERTEBRATA, MOLLUSCA, ARTICULATA, 

 and RADIATA. 



The distinguishing characters of these primary 

 groups may be briefly expressed as follows : 



