ANALOGIES OF GROUPS. 299 



be indisputably proved by analysis, that the MeliphagidcB 

 follow the Cinnyrid<e, and not the Pi-omeropida. This 

 disposition, again, would destroy the union of the three 

 aberrant groups into one, a fact which is all but esta- 

 blished by the Ptiloris paradiseus Sw. *, independent of 

 the many other mutual resemblances, of a general nature, 

 between the Promeropidce and the MeliphagidcB : it 

 seems, therefore, that we must account for this per- 

 plexing disturbance of such series on some other prin- 

 ciple. 



{SG'^.^ This brings us to the second question, whe- 

 ther this partial transportation of the series does not 

 depend upon mathematical principles of variation, re- 

 sulting from the different position which the groups on 

 one side of a circle occupy to those upon the other. 

 After much consideration on this abstruse question, I 

 regret not being able to answer it more fully : does it 

 not, in fact, belong more to the mathematician ? Be 

 this, however, as it may, I have uniformly observed 

 that similar transportations occur when typical are 

 compared with aberrant groups; but when all the groups 

 compared are typical, then these different types fall 

 into their natural series. As an instance of this, it must 

 be remembered, that, of the two groups we have been 

 comparing, one is an aberrant tribe, the other is a ty- 

 pical order : the subject, however, deserves much more 

 attention than I have yet been able to give to it. The 

 naturalist will readily perceive, however, that these ques- 

 tions are totally unconnected with that which regards the 

 definite denomination of groups, already noticed (268.), 

 whether they are typical or aberrant. 



{365.) This principle of definite denomination is most 

 important, as, from not having been then discovered, 

 all the diagrams of the "' Horse Entomologica;," where 

 these transportations occur in the situation of the groups, 

 are rendered completely erroneous. It is one of the 

 primary laws of nature that a typical group can never 

 become an aberrant one, and vice versa. 



• See ZooL Journal, vol. i. p. 479. j also North. Zool. vol. ii. p. 167. 



