106 Mr. Vigors's Repli/ to some Observations 



But to return to the subject more immediately before us.- — 

 From the foregoing observations and the authorities which have 

 been adduced to corroborate them, it may be summarily concluded 

 that the subdivision of an extensive genus like Psittaciis is not 

 merely philosoplncally correct, but conformable to the usual 

 process employed in Natural Science. The only groups whose 

 value and denomination can be in any wise considered definite, 

 are species. All the superiour assemblages of every degree arc 

 perfectly arbitrary, and are subject to variation as the species 

 included in them, and the modifications of form discernible 

 among these species, call for further subdivision. The only 

 question to be considered in respect to this subdivision is the im- 

 portance of the characters on which the intermediate groups are 

 founded. We are thus brought to the second point which I had 

 proposed to notice ; and I shall proceed to the examination of the 

 chief objection which has been levelled against the new genera of 

 the Psittudthe, that they have been instituted " upon minute and 

 valueless differences." 



If 1 were asked to point out what appears to be the greatest 

 modern improvement in Natural Science, I should say that it is 

 that mode of arrangement which results from the conviction that 

 there are no divisions in nature ; and in which accordingly groups 

 are established, not upon the difference, but upon the variation of 

 their characters. The naturalist seeks out the typical characters of 

 his larger groups at the point where they appear most strongly 

 developed, and then tracing their various modilications until they 

 may be said to evanesce, and give place imperceptibly to the 

 succeeding characters of the ueighbouriug groups, he fixes upon 

 these various modifications as ideal marks of separation between his 

 subdi visional groups. He is in this manner guided, not ])y detecting 

 distinct or opposing characters, but by tracing out the modifica- 

 tions of the same. The first suggestion of this mode of viewing 

 nature, in contradistinction to that which is founded upon a 

 supposed separation of groups, was made by Linnaeus, whose maxim 

 " Natura uhique varia semper iamen eadem," directly acknow- 

 ledges this principle. He had not himself materials sufficient to 

 act upon it invariably; and yet many of the genera which he 



