36 AFFINITIES AND CLASSIFICATION 



animals of saying which is most important, and yet 

 everyone feels that some one system alone deserves 

 to be called natural. The true relationship of 

 organisms is brought before one by considering 

 relations of analogy, an otter-like animal amongst 

 mammalia and an otter amongst marsupials. In 

 such cases external resemblance and habit of life 

 and the final end of ivhole organization very strong, 

 yet no relation 1 . Naturalists cannot avoid these 

 terms of relation and affinity though they use them 

 metaphorically. If used in simple earnestness the 

 natural system ought to be a genealogical (one); 

 and our knowledge of the points which are most 

 easily affected in transmission are those which we 

 least value in considering the natural system, and 

 practically when we find they do vary we regard 

 them of less value 2 . In classifying varieties the 

 same language is used and the same kind of 

 division : here also (in pine-apple) 3 we talk of the 

 natural classification, overlooking similarity of the 

 fruits, because whole plant differs. The origin of 

 sub-genera, genera, &c., &c., is not difficult on notion 

 of genealogical succession, and accords with what we 

 know of similar gradations of affinity in domesticated 

 organisms. In the same region the organic beings 

 are (illegible) related to each other and the external 

 conditions in many physical respects are allied 4 

 and their differences of same kind, and therefore 

 when a new species has been selected and has 

 obtained a place in the economy of nature, we 



1 For analogical resemblances see Origin, Ed. i. p. 427, vi. p. 582. 



2 " Practically when naturalists are at work, they do not trouble them- 

 selves about the physiological value of the characters.... If they find a 

 character nearly uniform,... they use it as one of high value," Origin, Ed. i. 

 p. 417, vi. p. 573. 



3 "We are cautioned... not to class two varieties of the pine-apple 

 together, merely because their fruit, though the most important part, 

 happens to be nearly identical," Origin, Ed. i. p. 423, vi. p. 579. 



4 The whole of this passage is obscure, but the text is quite clear, except 

 for one illegible word. 



