CLASSIFICATION. 279 



the class. There are always some properties common to all 

 things which are included. Others there often are, to which 

 some things, which are nevertheless included, are exceptions. 

 But the objects which are exceptions to one character are not 

 exceptions to another : the resemblance which fails in some 

 particulars must be made up for in others. The class, there 

 fore, is constituted by the possession of all the characters 

 which are universal, and most of those which admit of excep 

 tions. If a plant had the ovules erect, the stigmata divided, 

 possessed the albumen, and was without stipules, it possibly 

 would not be classed among the Rosaceae. But it may want 

 any one, or more than one of these characters, and not be 

 excluded. The ends of a scientific classification are better 

 answered by including it. Since it agrees so nearly, in its 

 known properties, with the sum of the characters of the class, 

 it is likely to resemble that class more than any other in those 

 of its properties which are still undiscovered. 



Not only, therefore, are natural groups, no less than any 

 artificial classes, determined by characters; they are consti 

 tuted in contemplation of, and by reason of, characters. But 

 it is in contemplation not of those characters only which are 

 rigorously common to all the objects included in the group, 

 but of the entire body of characters, all of which are found in 

 most of those objects, and most of them in all. And hence 

 our conception of the class, the image in our minds which is 

 representative of it, is that of a specimen complete in all the 

 characters ; most naturally a specimen which, by possessing 

 them all in the greatest degree in which they are ever found, 

 is the best fitted to exhibit clearly, and in a marked manner, 

 what they are. It is by a mental reference to this standard, 

 not instead of, but in illustration of, the definition of the class, 

 that we usually and advantageously determine whether any 

 individual or species belongs to the class or not. And this, 

 as it seems to me, is the amount of truth contained in the 

 doctrine of Types. 



We shall see presently that where the classification is made 

 for the express purpose of a special inductive inquiry, it is not 

 optional, but necessary for fulfilling the conditions of a correct 



