CLASSIFICATION. 421 



duce a limb, and in appearance there is no analogy. But 

 it was suggested by Blumeiibaeh that the healing of a 

 wound in the higher animals really represents in a lower 

 degree the power of reproducing a limb. That this is 

 true may be shown by adducing _ a multitude of inter- 

 mediate cases, each adjoining pair of which are clearly 

 analogous, so that we pass gradually from one extreme to 

 the other. Darwin holds, moreover, that any such re- 

 storation of parts is closely connected with that perpetual 

 replacement of the particles which causes every organized 

 body to be after a time entirely new as regards its con- 

 stituent substance. In short, we approach to a great 

 generalization under which all the phenomena of growth, 

 restoration, and maintenance of organs are effects of one 

 and the same power x . It is perhaps still more sur- 

 prising to find that the complicated process of sexual 

 reproduction in the higher animals may be gradually 

 traced down to a simpler and simpler form, which at last 

 becomes undistinguishable from the budding out of one 

 plant from the stem of another. By a great generalization 

 we may regard all the modes of reproduction of organic 

 life as alike in their nature, and varying only in com- 

 plexity of development y. 



Limits of Classification. 



Science can extend only so far as the power of accurate 

 classification extends. If we cannot detect resemblances, 

 and assign their exact character and amount, we cannot 

 have that generalized knowledge which constitutes science; 

 we cannot infer from case to case. It will readily be 



* Darwin, ' The Variation of Animals and Plants/ vol. ii. pp. 293, 

 359, &c. ; quoting Paget, ' Lectures on Pathology,' 1853, pp. 152, 164. 

 Y Ibid. vol. ii. p. 372. 



