358 Wisconsin Academy of Sciences, Arts and Letters, 



range those infimae species into larger groups 



and in doing this it is true that we are naturally and properly 

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

 ..... But though the groups are suggested by types, 

 I cannot think that the group, when formed, is determined 

 by the type; that in deciding whether a species belongs to 

 the group, a referemce is made to the type and not to the 



•characters The truth is, on the contrary, that 



■every genus or family is framed with distinct reference to 

 •certain characters, and is composed, first and primarily, of 

 species which agree in possessing all those characters. To 

 these are added, as a sort of appendix, such other species, 

 generally in small number, as possess nearly all the proper- 

 ties selected; wanting some of them one property, some 

 another, and which, while they agree with the rest almost 

 as much as those 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 anything else. And this resem- 

 blance itself is not, like resemblance between simple sensa- 

 tions, an ultimate fact unsusceptible of analysis. Even the 

 inferior degree of resemblance is created by the possession 



of common characters Nor can there he any 



real difficulty in representing, by an enumeration of char- 

 acters, the nature and degree of the resemblance which is 

 strictly sufficient to include any object in the class. There 



absolutely definable, inasmuch as its members will present exceptions to 

 every possible definition; and that the members of tlie class are united to- 

 :g3th3r oa'y by the c'.roum5l;anc3 that they are all m )r3 liks soaaa imagi- 

 nary avei'age race or average fish, than they resemble anything else. But 

 here, as before, I think the distinction has arisen eatirely from confusing 

 a transitory imperfection with an essential character. So long as our in- 

 formation concerning them is imperfect, we class all objects together ac- 

 cording to resemblances we feel, but cannot define; we group them around 

 types, in short. Thus, if you ask an ordinary pei'soa what kind of ani- 

 mals there are, he will probably say beasts, birds, reptiles, fishes, insects, 

 etc. Ask him to define a beast from a reptile and he cannot do it; but he 

 says, things like a cow or a horse ai-e beasts, and things like a frog or a 



