The geographical distribution of animals, with a study of the relations ...

;GG DISTRIBUTION OF ANIMALS. [part i.inconvenient. The one question then remains, whether theNearctic region should be kept separate, or whether it shouldform part of the Paleearctic or of the Neotropical regions.ProfessorHuxley 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 tobe said for both views, but both cannot be right ; and it will beshown in the latter part of this chapter that the Nearctic regionis, on the whole, fully as well defined as the PalaBarctic, by positivecharacters which differentiate it from both the adjacentregions. More evidence in the same direction will be found inthe Second Part of this work, in which the extinct faunas of theseveral regions are discussed.A confirmation of the general views here set forth, as to thedistinctness and approximate equivalence of the six regions, isto be found in the fact, that if any two or more of them are combinedthey themselves become divisions ofthe next lower rank,or " sub-regions " —and these will be very much more important,;both zoologically and geographically, than the subdivisions ofthe remaining regions,.It is admitted then that these six regionsare by no means of precisely equal rank, and that some of themare far more isolated and better characterized than others ; butit is maintained that, looked at from every point of view, theyare more equal in rank than any others that can be formedwhile in geographical equality, compactness of area, and facilityof definition, they are beyond all comparison better than anyothers that have yet been proposed forthe purpose of facilitatingthe study of geographical distribution. They may be arrangedand grouped as follows, so as to exhibit their variousrelations and affinities.Regions.jt ( Neotropical ... Austral zone Notogsea.°') Nearctic ) -n ,Boreal zonePai^arctic ...P1I Ethiopian P1 , . .Palaeogaea' 0riental jPalaeotropical zone\IJArctogaaa.\ Australian ... Austral zone Notogsea.The above table shows the regions placed in the order followedin the Fourth Part of this work, and the reasons for which are