ANALOGIES OF GROUPS. 299 
be indisputably proved by analysis, that the Meliphagide 
follow the Cinnyride, and not the Promeropide. 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 Promeropide and the Meliphagide: it 
seems, therefore, that we must account for this per- 
plexing disturbance of such series on some other prin- 
ciple. 
(364.) This brings us to the second question, whe- 
ther this partial transpertation 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 al/ 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 “ Hore Entomologice,”’ 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 versd. 
* See Zool, Journal, vol, i. p. 479.3 also North. Zool, vol, ii. p. 167. 
