404 CLASSlIlCAfiO^. 



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 description 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 be- 

 lieve 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 charac- 

 ters, 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 classi- 

 fication 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 even be given as a 

 general rule, that the less any part of the organization is 



