304 OPERATIONS SUBSIDIARY TO INDUCTION. 



if we made it our study to adopt the classification 

 which would involve the least peril of similar rap- 

 prochemens, we should return to the obsolete division 

 into trees, shrubs, and herbs, which although of pri- 

 mary importance with regard to mere general aspect, 

 yet (compared even with so petty and unobvious a 

 distinction as that into dicotyledones and monocoty- 

 ledones) answers to so few differences in the other 

 properties of plants, that a classification founded on it 

 (independently of the indistinctness of the lines of 

 demarcation,) would be as completely artificial and 

 technical as the Linnsean. 



Our natural groups, therefore, must often be 

 founded not upon the obvious, but upon the unob- 

 vious properties of things, when these are of greater 

 importance But in such cases it is essential that 

 there should be some other property or set of proper- 

 ties, more readily recognizable by the observer, which 

 co-exist with, and may be received as marks of, the 

 properties which are the real groundwork of the clas- 

 sification. A natural arrangement, for example, of 

 animals, must be founded in the main upon their 

 internal structure, but (as M. Comte justly remarks) it 

 would be absurd that we should not be able to deter- 

 mine the genus and species of an animal without first 

 killing it. On this ground, M. Comte gives the pre- 

 ference, among zoological classifications, to that of M. 

 de Blainville, founded upon the differences in the 

 external integuments ; differences which correspond, 

 much more accurately than might be supposed, to 

 the really important varieties, both in the other parts 

 of the structure, and in the habits and history of the 

 animals. 



This shows, more strongly than ever, how exten- 

 sive a knowledge of the properties of objects is neces- 



