EVIDENCE FROM CLASSIFICATION 31 



of evolution. This, however, is a metaphysical, 

 rather than a scientific question, and has no im- 

 mediate bearing upon the evidences for the theory 

 of evolution. 



As has already been pointed out, the evidence for 

 the theory consists of several distinct and independ- 

 ent lines of testimony, so to speak, and it will con- 

 duce to clearness of treatment, if each of these lines 

 is dealt with separately, though their action and 

 reaction upon one another must not be overlooked. 

 In the first place, we may take up the argument from 

 classification, which is the most obvious one and has 

 the additional historic interest of being the line along 

 which Lamarck and Darwin approached and reached 

 their primary generalizations. It was, in short, the 

 problem of species which led those great naturalists 

 to abandon the current belief in the fixity and im- 

 mutability of living types and to adopt the hypothesis 

 of development. To repeat, in part, the quotation 

 from Lamarck given in the first lecture: 'The diffi- 

 culty which I know, from my own experience, is now 

 felt in distinguishing species . . . has convinced me 

 that our species have but a limited existence and, 

 for the most part, differ from neighbouring ones only 

 by shades which it is difficult to express." (See 

 ante, p. 9.) 



The object of classification is to arrange the ex- 

 traordinarily manifold assemblages of animals and 

 plants in groups of ascending comprehensiveness, 

 which shall express, so nearly as the present state of 



