i GEOGRAPHICAL DISTRIBUTION 1 5 



strictly speaking, impossible, since any group may have a 

 decided affinity to more than two others. This Classification, 

 beginning (as Birds themselves must have begun) with the lower 

 forms, takes us, except in the Oscines, as far as the Families, 

 which in most cases are fairly distinguishable, though of very 

 variable value. Coming to Genera, and still more to Species, 

 the opinions of authorities often differ so widely, that at present 

 an attempt to reconcile them is hopeless. It cannot be denied 

 that Genera and Species are merely " convenient bundles," and 

 that divisions of either, if carried too far, defeat the object for 

 which Classification is intended. Genera are only more distinct 

 from Species, and Species from Races, because the intervening 

 links have disappeared ; and, if we could have before us the 

 complete series which, according to the doctrine of Evolution, has 

 at some time existed, neither Genus nor Species would be cap- 

 able of definition, any more than are Eaces in many cases ; while 

 the same remark will apply to the larger groups. 



From these Races or Geographical variations we may not 

 unnaturally turn to Geographical Distribution. It will always 

 be credited to Ornithology that the interesting study of the Geo- 

 graphical Distribution of Animals was first placed on a scientific 

 basis as a result of the study of Birds. This was effected by Mr. 

 Sclater, whose division of the Globe into Six " Regions " the 

 Palaearctic, Ethiopian, Indian, and Australian, forming one 

 group the " Old World " (Palaeogaea)\ and the Nearctic and Neo- 

 tropical, forming a second the " New World " (Neogaeci) ; was 

 announced in 1858 (J. Linn. Soc. ii. pp. 130-145). His scheme, 

 being solely grounded on Ornithological considerations, was 

 accepted with scarcely any modification by Mr. Wallace in his 

 great work (Geograpli. Distrib. of Animals, 1876), and by the 

 majority of zoologists, though some demurred, and among them 

 Huxley, who, in especial reference to Birds, shewed (Proc. Zool. 

 Soc. 1868, pp. 313-319) that there was more reason to divide 

 the earth's surface latitudinally than longitudinally, and that 

 Four Regions were better than Six these four being (1) 

 Arctogaea, comprising Mr. Sclater's Indian, Ethiopian, Palae- 

 arctic, and Nearctic; (2) Austro- Columbia, corresponding with 

 the Neotropical; (3) Australasia; and (4) New Zealand the 

 last three being combined as Notogaea. In 1882 Prof. Heilprin 

 proposed to unite Mr. Sclater's Palaearctic and Nearctic under 



