PROGRESS OF SYSTEMATIC ZOOLOGY. 389 



The doctrine of Circular Progression has been 

 propounded principally by Mr. Macleay; although, 

 as he has shown 13 , there are suggestions of the 

 same kind to be found in other writers. So far as 

 this view negatives the doctrine of a mere linear pro- 

 gression in nature, which would place each genus 

 in contact only with the preceding and succeeding 

 ones, and so far as it requires us to attend to more 

 varied and ramified resemblances, there can be no 

 doubt that it is supported by the result of all the 

 attempts to form natural systems. But whether 

 that assemblage of circles of arrangement which is 

 now offered to naturalists, be the true and only 

 way of exhibiting the natural relations of organized 

 bodies, is a much more difficult question, and one 

 which I shall not here attempt to examine; although 

 it will be found, I think, that those analogies of 

 science which we have had to study, would not fail 

 to throw some light upon such an inquiry. The 

 prevalence of an invariable numerical law in the 

 divisions of natural groups, (as the number Jive is 

 asserted to prevail by Mr. Macleay, the number ten 

 by Fries, and other numbers by other writers,) 

 would be a curious fact, if established ; but it is 

 easy to see that nothing short of the most consum- 

 mate knowledge of natural history, joined with 

 extreme clearness of view and calmness of judg- 

 ment, could enable any one to pronounce on the 

 attempts which have been made to establish such 



18 Linn. Trans, vol. xvi. p. 9. 



