66 DISTRIBUTION OF ANIMALS. [PART I. 
inconvenient. The one question then remains, whether the 
Nearctic region should be kept separate, or whether it should 
form part of the Palearctic or of the Neotropical regions. Pro- 
fessor Huxley and Mr. Blyth advocate the former course ; Mr. 
Andrew Murray (for mammalia) and Professor Newton (for birds) 
think the latter would be more natural. No doubt much is to 
be said for both views, but both cannot be right; and it will be 
shown in the latter part of this chapter that the Nearctic region 
is, on the whole, fully as well defined as the Palearctic, by posi- 
tive characters which differentiate it from both the adjacent 
regions. More evidence in the same direction will be found in 
the Second Part of this work, in which the extinct faunas of the 
several regions are discussed. 
‘A confirmation of the general views here set forth, as to the 
distinctness and approximate equivalence of the six regions, is 
to be found in the fact, that if any two or more of them are com- 
bined they themselves become divisions of the next lower rank, 
or “ sub-regions ;”—and these will be very much more important, 
both zoologically and geographically, than the subdivisions of 
the remaining regions. It is admitted then that these six regions 
are by no means of precisely equal rank, and that some of them 
are far more isolated and better characterized than others; but 
it is maintained that, looked at from every point of view, they 
are more equal in rank than any others that can be formed ; 
while in geographical equality, compactness of area, and facility 
of definition, they are beyond all comparison better than any 
others that have yet been proposed for the purpose of facilitat- 
ing the study of geographical distribution. They may be ar- 
ranged and grouped as follows, so as to exhibit their various 
relations and affinities. 
Regions. 
Neogeea } a eOrtoAl are Austral zone......... Notogea. 
pa Boreal zone ......... 
PAL@ARCTIC ... § ‘Arceas 
ae ETHIOPIAN ...... Palzotropical zone rp 
= ORIENTAL ........ pce P 
AUSTRALIAN ... Austral zone......... Notogeea. 
The above table shows the regions placed in the order followed 
in the Fourth Part of this work, and the reasons for which are 
