504 OPERATIONS SUBSIDIARY TO INDUCTION. 



are perhaps differences of kind; the lines of demarkation which divide 

 those classes seem (though even on this I would not pronounce positively) 

 to go through the whole nature of the plants. But the different species 

 of a genus, or genera of a family, usually have in common only a limited 

 number of characters. A Rose does not seem to differ from a Rubus, or 

 the Umbelliferae from the Ranunculaceae, in much else than the characters 

 botanically assigned to those genera or those families. Unenumerated dif- 

 fei'ences certainly do exist in some cases; there are families of plants 

 which have peculiarities of chemical composition, or yield products having 

 peculiar effects on the animal economy. The Cruciferae and Fungi contain 

 an unusual proportion of nitrogen ; the Labiatas are the chief sources of 

 essential oils, the Solanese are very commonly narcotic, etc. In these and 

 similar cases there are possibly distinctions of Kind ; but it is by no means 

 indispensable that there should be. Genera and Families may be eminent- 

 ly natural, though marked out from one another by properties limited in 

 number; provided those properties are important, and the objects con- 

 tained in each genus or family resemble each other more than they resem- 

 ble any thing which is excluded from the genus or family. 



After the recognition and definition, then, of the infimm species, the next 

 step is to arrange those infimm species into larger groups: making these 

 groups correspond to Kinds wherever it is possible, but in most cases with- 

 out any such guidance. And in doing this it is true that we are naturally 

 and properly guided, in most cases at least, by resemblance to a type. We 

 form our groups round certain selected Kinds, each of which serves as a 

 sort of exemplar of its group. But though the groups are suggested by 

 types, I can not think that a group when formed is determined by the type ; 

 that in deciding whethxir a species belongs to the group, a reference is made 

 to the type, and not to the characters ; that the characters " can not be ex- 

 pressed in words." This assertion is inconsistent Avith Dr.Whewell's own 

 statement of the fundamental principle of classification, namely, that "gen- 

 eral assertions shall be possible." If the class did not possess any charac- 

 ters in common, what general assertions would be possible respecting it? 

 Except that they all resemble each other more than they resemble any thing 

 else, nothing whatever could be predicated of the class. 



The truth is, on the contrary, that every genus or family is framed with 

 distinct reference to certain characters, and is composed, first and princi- 

 pally, of species which agree in possessing all those characters. To these 

 are added, as a sort of appendix, such other species, generally in small num- 

 ber, as possess nearly all the i)roperties selected ; wanting some of them 

 one property, some another, and which, while they agree with the rest al- 

 most as much as these agree with one another, do not resemble in an equal 

 degree any other group. Our conception of the class continues to be 

 grounded on the characters ; and the class might be defined, those things 

 which either possess that set of characters, or resemble the things that do 

 so, more than they resemble any thing else. 



And this resemblance itself is not, like resemblance between simple sen- 

 sations, an ultimate fact, unsusceptible of analysis. Even the inferior de- 

 gree of resemblance is created by the possession of common characters. 

 Whatever resembles the genus Rose more than it resembles any other ge- 

 nus, does so because it possesses a greater number of the characters of that 

 genus than of the characters of any other genus. Nor can there be any 

 real difficulty in representing, by an enumeration of characters, the nature 

 and degree of the resemblance which is strictly sufficient to include any ob- 



