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 Palsearctic 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 Pala?arctic, 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. 



>r | Neotropical ... Austral zone Notogsea. 



*> ) Nearctic ) -n ■, \ 



Pal.earctic ... Boreal zone 



P1 I Ethiopian L , f . . JArctogaea. 



Palseogsea' Oriental .. ,.. ( Palaeotro P lca l zone 



\ Australian ... Austral zone Notogsea. 



The above table shows the regions placed in the order followed 

 in the Fourth Part of this work, and the reasons for which are 



