342 CLASSIFICATION. [CHAP. XIV 



characters. We know, for instance, that minerals and the 

 elemental substances can be thus arranged. In this case there 

 is of course no relation to genealogical succession, and no cause 

 can at present be assigned for their falling into groups. But with 

 organic beings the case is different, and the view above given 

 accords with their natural arrangement in group under group ; 

 and no other explanation has ever been attempted. 



Naturalists, as we have seen, try to arrange the species, genera, 

 and families in each class, on what is called the Natural System. 

 But what is meant by this system? Some authors look at it 

 merely as a scheme for arranging together those living objects 

 which are most alike, and for separating those which are most 

 unlike ; or as an artificial method of enunciating, as briefly as 

 possible, general propositions, that is, by one sentence to give 

 the characters common, for instance, to all mammals, by another 

 those common to all carnivora, by another those common to the 

 dog-genus, and then, by adding a single sentence, a full descrip- 

 tion is given of each kind of dog. The ingenuity and utility of 

 this system are indisputable. But many naturalists think that 

 something more is meant by the Natural System ; they believe 

 that it reveals the plan of the Creator ; but unless it be specified 

 whether order in time or space, or both, or what else is meant by 

 the plan of the Creator, it seems to me that nothing is thus added 

 to our knowledge. Expressions such as that famous one by 

 Linnaeus, which we often meet with in a more or less concealed 

 form, namely, that the characters do not make the genus, but that 

 the genus gives the characters, seem to imply that some deeper 

 bond is included in our classifications than mere resemblance. I 

 believe that this is the case, and that community of descent the 

 one known cause of close similarity in organic beings is the bond, 

 which though observed by various degrees of modification, is 

 partially revealed to us by our classifications. 



Let us now consider the rules followed in classification, and the 

 difficulties which are encountered on the view that classification 

 either gives some unknown plan of creation, or is simply a scheme 

 for enunciating general propositions and of placing together the 

 forms most like each other. It might have been thought (and 

 was in ancient times thought) that those parts of the structure 

 which determined the habits of life, and the general place of each 

 being in the economy of nature, would be of very high importance 

 in classification. Nothing can be more false. No one regards the 

 external similarity of a mouse to a shrew, of a dugong to a whale, 

 of a whale to a fish, as of any importance. These resemblances, 

 though so intimately connected with the whole life of the being, 

 are ranked as merely " adaptive or analogical characters ; " but to 

 the consideration of these resemblances we shall recur. It may 



