I GEOGRAPHICAL DISTRIBUTION 15 
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 Familhes, 
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 Races 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- 
eraphical 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 
Palaearetic, Ethiopian, Indian, and Australian, forming one 
eroup—the “ Old World” (Palacogaea); and the Nearctic and Neo- 
tropical, forming a second—the “ New World” (Neogaea) ; was 
announced in 1858 (J. Linn. Soc. il. pp. 130-145). His scheme, 
being solely grounded on Ornithological considerations, was 
accepted with scarcely any modification by Mr. Wallace in his 
great work (Geograph. 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. 315-319) 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 
