ON THE NATURAL SYSTEM. li 



alternative than to consider the primary circles of every group as 

 equal in rank and value. 



But I wish not to attach too much importance to a term, or, in 

 drawing up these tables of affinities, to depart more than is necessary 

 from the usual mode of exhibiting circular groups. I have, therefore, 

 in every instance, detailed the subordinate divisions of the aberrant 

 groups, although, without this explanation, such a plan might convey 

 an erroneous impression of their relative value. 



I must now advert to another, and, in my estimation, an unques- 

 tionable property of natural arrangement : this is, the direct union 

 of typical groups, without the intervention of those which are aber- 

 rant. A vague suspicion of something like this first occurred to me 

 when studying the affinities of the Laniadce, in the year 1824*. This 

 property, however, belongs but to very few groups, since it has only 

 been detected in such as are pre-eminently abundant in species, and 

 are not of a higher rank than families. Beyond such groups, the 

 higher we ascend, the more dissimilar are the typical groups in ap- 

 proximating circles ; until, in looking to a diagram of the vertebrated 

 animals, (such, for instance, as that in the Horce Ent., p. 318,) not only 

 does all appearance of affinity between the external or typical divisions 

 vanish, but it becomes even difficult, in some instances, to trace their 

 analogy. These inferior typical groups, indeed, may be said to have 

 three distinct relations of affinity : one to that which precedes it ; 

 another to that by which it is followed ; and a third which unites it 

 to a group out of its own proper circle. The two first, on this account, 

 may be termed internal ; the latter, external. This, however, is a 

 question so abstruse, and requires such nicety of investigation, that, for 

 the present, I should rather, perhaps, put it as a query, than consider 

 it as a demonstrated fact. At the same time, I must confess my utter 

 inability to reconcile, by any other theory, the evident and universally 

 acknowledged affinity between the Thamnophilina and the Myothe- 

 rinee ; between the Merulince and the Philomelina ; and more espe- 

 cially between the typical Setophagcs and the typical Sylvicoke. 



* Zool. Journ., i. p. 302. 



