xllV INTRODUCTORY OBSERVATIONS 



Entomologies, is its tendency to raise Zoology to the rank of a demon- 

 strative science. By proving that natural affinities were circular, it 

 established at the same time the existence of definite groups ; from 

 which, of course, if any part was taken away, and placed in another 

 group, a violation of natural affinities would inevitably follow, and both 

 groups be rendered artificial. Now this principle, as it appears to me, 

 has been either completely overlooked or essentially violated by the 

 disciples of this school. They express their opinion that a genus, 

 which seems allied to two different families, " may be placed in either, 

 according to its external characters*;" and if these two families are 

 in juxtaposition, " it is immaterial to which of them it may eventually 

 be referred." Now, if an arrangement be artificial, that is, framed 

 merely to assist the memory, this mode of proceeding would be very 

 well ; but if such a principle be admitted in the theory of Mr. Mac- 

 leay, it completely destroys all his idea of definite groups, and leaves 

 every one to describe their circles at their own good will and pleasure. 

 Again ; another most important definition, contained in the same 

 volume, relates to the nature and value of those groups which are 

 there denominated genera, and which are shown to contain certain 

 types of form, termed sub-genera. It is, moreover, proved that every 

 zoological genus thus characterized returns into itself, and forms a 

 circle. It matters not whether this definition of a zoological genus 

 agrees with that which has been given to the word by logicians ; yet 

 one of the most zealous disciples of Mr. Macleay has rejected his 

 application of this word, which is definite, and has advocated another, 

 confessedly founded upon metaphysical reasoningf and mere opinion J. 

 It is owing to these and to similar misconceptions, which the disciples 

 of Mr. Macleay have fallen into, that the theory itself has been of 

 late so severely attacked, and has even lost some of its supporters. 

 Certain, however, it is, that these inconsistencies are nowhere to be 

 found in the writings of this distinguished master. He has re- 

 peatedly warned his disciples on the facility of making circles and 

 quinary divisions, when unsupported by those tests which he has him- 



* Vigors, Zool. Journ., i., p. 397. t Zool. Journ., iii., p. 97. % Ibid., i., p. 341. 



