NATURAL SYSTEMS. 199 



or as if each had been created upon distinct plans. 

 So in regard to fish, or reptiles, or insects ; each is 

 successively arranged independently of the others, 

 as if they were so many isolated systems, and not 

 merely portions of one. We may, perhaps, be cen- 

 sured for dwelling upon the defects of some of the 

 most influential authorities of the day ; but it should 

 be remembered, that error must be removed before 

 truth can be established. Natural history, like all 

 other human knowledge, is progressive ; nor does it at 

 all follow, that, because our predecessors may have 

 been mistaken on some points, we are to set aside their 

 authority, or undervalue their labours, upon others. 

 It has been well said of such men, that even theii 

 errors are the errors of genius ; and that they are 

 calculated, if rightly used, to teach wisdom to such 

 as come after them. Let it be remembered, also, 

 that we are now investigating natural history as we 

 would do any other of the physical sciences ; and that 

 we can only hope to advance its interests by making it 

 subject to the same general principles, and the same 

 rules of investigation, which are applicable to all. 

 There cannot be a doubt, that mixed systems, how- 

 ever objectionable upon the grounds we have stated, 

 have done incalculable good, and have brought the 

 science to such an advanced state, that, in these 

 latter days, a glimpse of the natural system has at 

 length opened upon us. 



(135.) We shall now shortly consider the nature 

 of those classifications which aim at exhibiting uni- 

 form principles and general results, and which we 

 have consequently termed natural systems. The 

 term, we before observed, is in some respects ob- 

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