I04 EVOLUTION, GENETICS, AND EUGENICS 



that upon their results must be built synthetic studies, if taxonomy 

 is to fulfil its purpose. 



THE METHOD OF CLASSIFICATION 



CHARLES DARWIN' 



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 utiHty 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 charac- 

 ters, seem to imply that some deeper bond is included in our classifica- 

 tions 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 



^ From The Origin of Species. 



