PROGRESS OF ICHTHYOLOGY. 403 



establishing a subordination of characters. And 

 each of these answers had its difficulty, of which 

 the solution appeared to be, that in attempting to 

 form natural orders we are really guided by a latent 

 undeveloped estimate of physiological relations. 

 Now this principle, which was so dimly seen in the 

 study of vegetables, shines out with much greater 

 clearness when we come to the study of animals, in 

 which the physiological relations of the parts are 

 so manifest that they cannot be overlooked, and 

 have so strong an attraction for our curiosity that 

 we cannot help having our judgments influenced by 

 them. Hence the superiority of natural systems 

 in zoology would probably be far more generally 

 allowed than in botany ; and no arrangement of 

 animals which, in a large number of instances, vio- 

 lated strong and clear natural affinities, would be 

 tolerated because it answered the purpose of ena- 

 bling us easily to find the name and place of the 

 animal in the artificial system. Every system of 

 zoological arrangement may be supposed to aspire 

 to be a natural system. But according to the various 

 habits of the minds of systematizers, this object was 

 pursued more or less steadily and successfully ; and 

 these differences came more and more into view 

 with the increase of knowledge and the multiplica- 

 tion of attempts. 



Bloch, whose ichthyological labours have been 

 mentioned, followed in his great work the method 

 of Linnaeus. But towards the end of his life he 



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