140 Wisconsin Academy of Sciences^ Aris^ and Letters. 



largely done this worh for us, has made the comparison and given 

 us the results, and herein lies its especial fitness to be our guide. 

 A mental power and a physical form are so diverse in tlieir 

 nature that, considered independently, it is not apparent how 

 they can be rationally compared at all. But the nervous sys- 

 tem is a common medium for their action and furnishes the 

 means of comparison. Where two organs of diverse natures 

 act by means of separate and exclusive ganglia, those ganglia, 

 it must be admitted, furnish the true means of comparison. 

 And though the ganglia presiding over the various organs 

 may not be thus distinct and exclusive in general, that does 

 not vitiate the principle, but only affects its application. 



Furthermore, the objection to this single organism as a basis 

 is very much answered, so far as it has any bearing on grada- 

 tion, when it is remembered that the nervous system is com- 

 prehensive in its nature. It is headquarters and source of 

 co-ordination for all the functions of the whole system. It 

 in a sense comprehends them all. This is a fact of supreme 

 importance in gradation though it may be valueless in classifi- 

 cation. 



The nervous system is likewise rep)resentative in its nature. 

 Complication in any other system of the body implies corre- 

 s]Donding complication of the nervous sj^stem, and implies it 

 in terms of the common standai'd. 



Moreover, the nervous system comprises the highest fomi 

 of organized matter. We should then expect its forms to be 

 most indicative of rank. 



And further, while it is generally conceded that intellectual 

 characteristics have little value in classification, if indeed they 

 should not be entirely ignored, they must from the very 

 nature of the case form a most important element in the esti- 

 mation of rank. Classification should be based upon struct- 

 ural affinities, gradation upon functional power. Classification, 

 if true, is but an interpretation of nature ; gradation is a judg- 

 ment passed upon it. Classification is natural ; gradation is 



