r,74 CLASSIFICATION. Chap. XIII 



Naturalists, as we have seen, try to arraiioc the species, 

 genera, and families in each class, on what is called the Natu- 

 ral System. But -what is meant by this system ? Some 

 authors look at it merely as a scheme for arranginj^ tog'ethcr 

 those llvina^ objects which are most alike, and for separating 

 those which are most inilike ; or as an artificial means for 

 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 conunon to the dog-genus, and then, by adding 

 a single sentence, a full description is given of each kind of 

 dog. The ingenuity and utility of this system are indispu- 

 table. But many naturalists think that something more is 

 meant ])y the Natural System ; they believe that it reveals the 

 plan of the Creator ; but, unless it be specified Avhether 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. Such expressions as that fiimous one by Lin- 

 nieus, and which wc often meet with in a more or less con- 

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

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

 thing more is included in our classification than mere resem- 

 blance. I believe that something more is included, and that 

 propin(juity of descent — the only known cause of the similarity 

 of organic beings — is the bond, hidden as it is by various de- 

 grees of modification, which 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 imknown plan of creation, or is 

 simply a scheme for enunciating general propositions and of 

 jilacing together the forms most like each other. It might 

 have been thought (and Avas 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 reseml)lances, though so intimate- 

 ly connected with the whole life of the being, are ranked as 

 merely " adaptive or analogical characters ; " but to the con- 

 sideration of these resemblances we shall recur. It may even 

 be given as a general rul(>, that the less nny part of the organi- 



